Scratch mixing developers: a problem?

Discussion in 'Black and White' started by rowland_mowrey, Jun 16, 2004.

  1. I have seen several posts here that recommend using the swimming pool
    pH adjust Sodium Carbonate in developer solutions.

    I was out buying pool supplies and thought "What the heck, why not.
    Save some money on the reagent grade." Then, I looked at the label
    and it said 98% pure.

    "Well, what does that mean", sez I to me.

    After thinking about it, it could mean additional water of hydration,
    if any, it could mean any other element such as lead, iron, copper or
    even halide ions such as bromide, chloride, and iodide, in fact; it
    could mean just about anything including sand.

    Considering this, I figure that if it were something like sand, I
    wouldn't want to trust my negatives to it, and if it were a halide
    ion contaminant, I wouldn't trust the repeatability of any developer
    mixed with this chemical. Iron contamination can fog film and paper.

    I know that some of you have had good or excellent results this way,
    but on the other hand, you may have been lucky so far. I don't know
    and there is really no way to tell.

    I don't know about you, but I just ordered another 5 lbs of Anhydrous
    sodium carbonate from my regular supplier of high quality chemicals.
    I don't want to take a chance with my films and paper prints, and I
    thought I would let you know my feelings.

    I want to enjoy my photography, not worry about it.

    Ron Mowrey
  2. I presume you know for a fact that the stuff you got is in fact high grade?

    I can't see how a supplier of chemicals for swimming pools could get away with including lead or most other heavy metals. I believe the label implies that the 2% are inert ingredients. At any rate, you can get the MSDS sheet on the internet.

    I found out that way the the Chem Out sold by BioGuard for swimming pool use is 100% sodium sulfite.

    By the way, how do you know what purity you actually need for photographic work? I seriously doubt that the manufacturers of commercial developers use reagent grade or USP.
  3. Photographic work requires photographic grade chemicals. These are purer than industrial grade but less pure than USP and reagent grade. The 98% purity is fine; where the problem might lie is if the 2% contains a lot of metallic impurities. You could always give it a test.
  4. >> I seriously doubt that the manufacturers of commercial developers use reagent grade or USP <<

    Actually, I imagine they pretty much all either use photographic grade or do specific analytical screening of commercial grade.

    On occasion, a question has come up here to the effect of "what is photographic grade?" when buying chemicals. Although I don't think I previously responded to any of those questions, I'm sure you two guys, in particular, can appreciate the existence of a substantial set of ANSI (and presumably now also ISO) standards for photo grade chemicals.

    Those photograde standards typically specify both purity and allowable levels of specified "contaminants" based on the forseeable uses of those chemicals. For example, ammonium thiosulfate would normally be used in fixer and trace amounts of iron would not be of much concern. However, sodium sulfite could readily be used in either fixer OR developer; due to the possible use in developer, the specified iron limits would be very low. So on occasion, someone who uses a non-typical process might find that even photograde chemical are not good enough in some cases.

    Although I've had substantial experience in these areas (for Ron's info, I know what C-42 is), I don't personally scratch mix my own. However, if I WERE to start scratch mixing, I think I would kind of take Ron's viewpoint for serious work. If I had personal knowledge about specific brands (either via chemical analysis or knowledge of the manufacturing process or simply from previous use), I'd be willing to use them. As far as just playing around with my own non-critcal work, I guess I'd be willing to try cheaper off the shelf alternatives.

    A line I've used quite a bit in the past, when someone I know asks for photo advice, is, "which do you have more of: time or money?". I think this kind of applies here.
  5. Some years back, I had occasion to chat with someone who happened to be employed by a very large chemical manufacturer that shall remain nameless. He mentioned that his employer sold large quantities of chemicals (I think the one he mentioned specifically was potassium bromide, but I may be wrong, it's been many years) to a very large photographic materials manufacturer that shall also remain nameless.

    Anyhow, he said that the photographic manufacturer would evaluate samples of different batches, and then after examining the results of their tests, advise the chemical manufacturer as to how long to store the chemicals (and perhaps at what temperatures, etc., but I cannot recall) before shipping them.

    These instructions pertained to each batch. The photographic manufacturer went to great lengths to ensure that each batch would be properly aged and handled prior to shipment.

    The workers at the chemical manufacturer, according to the person mentioned above, then loaded up and shipped whatever loads of the chemical they had on hand, with no regard to dates, times, batch numbers, etc.

    He told me that it was no big deal, since they'd be testing it again anyway when they received it. (I believe that may have been conjecture on his part, but I have no way of knowing.)
  6. Inert ingredients indeed.

    Sand is inert, but harmful as an abrasive in a developer.

    NaCl and NaBr are inert in a swimming pool chemical, but 2% in carbonate means that for every 100 g you have 2 g of halide salt, or if you are mixing a developer that requires 50 g/l of carbonate, you are getting 1 g/l extra halide. That can do a lot to a developer.

    That is a hypothetical example, and I doubt if lead is present, but Iron salts or copper salts would be inert by that definition. A mix of halide salts would be inert. Why bother when I can get good chemicals elsewhere that are at least photographic grade.

    BTW, I used reagent grade at KRL to scratch mix all chemicals. The specs were passed on to the mix room and then to the scale up mix lab and they followed our recommendations for purity level, whatever they might be.

    Ron Mowrey
  7. "These are purer than industrial grade"

    Don't be sure about that. A while back I posted a link to a company selling Sodium Sulfite. The photo grade was the lowest quality.

    The real question is does it make sense to run a plant making multiple grades of the same chemical? I'm going to go out on a limb and say for most things no. It's not like thier adding stuff to the chemicals are they? Is the photo industry really big enough to have plants providing chemicals just for them? Or is the photo industry a relatively small drop in the bucket?
  8. Life is full of FUD (fear, uncertainty, & doubt), and I'll admit to thinking more than I should about chemical purity. For serious research, reagent grade chems are great, but I wouldn't want to pay the price. They're vastly more expensive then a few decades ago. Mostly I buy from Photographer's Formulary, but just haven't had any problems with the pool chems or borax from the supermarket. Actually, we don't know where PP gets the stuff either, or its chemical analysis, though some of the grinding (milling?) leaves much to be desired. A while back I had some communications with Bill Troop on the topic, and it seems most chems are much purer today than in the past. As an example, we have no idea what the actual content of G. Crawley's potassium carbonate was when he formulated FX2. He used a crystalline form with some unknown percentage of bicarbonate and who knows what else. Mixing per his recipe today probably doesn't give you the same developer he originally tested. There were other routine contaminants in some developers that aren't present today, and could have a profound effect on the results. Apparently there are several processes to produce glycin, and the end result is different for each one. Consider that any chemical company worth its name would have a spectrograph of some sort. Way back, they had to run a series of tests, and if they didn't test for a particular contaminant, they didn't know about it. Today, there's no question about the content, at least as far as the maker is concerned. IMHO, your odds of getting extremely high quality chemicals today is far better than in the past, and you won't find the chem companies making a bunch of different grades unless economically justified.
  9. >> [Conrad] ...and I'll admit to thinking more than I should about chemical purity. <<

    Ok, I'll admit to knowing more about it than what I say here.

    >> [Robert Davis] The real question is does it make sense to run a plant making multiple grades of the same chemical? I'm going to go out on a limb and say for most things no. <<

    Well, sure, sometimes it makes sense. Let's say your bulk material has some contaminants but is acceptable for a certain grade; you would ship it "as is". In order to sell as another grade, you might run it through some sort of purification process; possibly multiple purification steps are needed, but you would likely stop as soon as you achieved the specs.

    Alternatively, there may be different manufacturing processes. One process may be extraordinarily cheap and makes a fine technical grade chemical. But perhaps that process introduces something known to be a potential contaminant for photo use. so the plant may have two different manufacturing processes. If they make a pharmaceutical grade, the entire process is subject to a large train of requirements, at least in the Us. It's probably not economical to make technical grades on a pharmaceuticl line.

    >> [Robert] Don't be sure about that. A while back I posted a link to a company selling Sodium Sulfite. The photo grade was the lowest quality. <<

    Robert, is this the thread?
    And is this the link?

    In that link, here is something I see under specifications for anhydrous sodium sulfite (this is just like one of the examples I used above):

    Iron (Fe) 10.0 ppm max[for photo grade], 20 ppm max[technical grade], and 40 ppm max [food grade].

    I would answer Robert back with, "don't be so sure the photo grade is lowest quality". Apparently the iron level is considered more critical for photographic use. This is probably because it might be used in developers. If you were going to use it for a FIXER, however, hopefully you know that iron is not much of a concern and the plain technical grade is fine.

    I guess the bottom line here is that different grades can be used for different purposes, and different impurities are allowable for different uses. If you use official photo grade for everything, you're probably pretty safe. Alternatively, if you are short on money (but have time) or simply enjoy playing with the chemistry, it might be worth trying alternatives. Just don't be too upset if one day your process goes bad for no apparent reason.
  10. Bill;

    Thanks for that last post. I was looking up similar information for a post and you saved me a lot of trouble.

    Suffice it to say, most reagant grade chemicals are 99% pure, not 98% pure. That 1% may or may not be important, but what Bill says is true. Photographic grade is special stuff.

    Here is an example. When EK buys photograde NaBr, it must be nearly completely free of Iodide and Chloride. When EK buys NaCl photo grade, it must be free of Bromide and Iodide. Why? The other halides cause serious problems if found in the developer, and they will ruin an emusion.

    Iodide can even do bad things in bleaches and bleach fixes. Iodide and some sulfur compounds can, under certain circumstances, just about halt bleaching reactions in FeEDTA bleaches and fixes.

    I just put that original post up in the public interest after an observation on a shopping trip. I didn't buy the carbonate at the pool store. I came home and ordered another 5 lbs from my favorite supplier. I'm not trying to scare anyone or raise a false alarm. I honestly don't know if there is a problem at all. It is just a public service post.

    I do know this. If the impurity is as harmless as sand, I still don't want it in any of my solutions.


    Ron Mowrey
  11. But photo grade isn't reagent grade. Is it?

    Onto the difference between the food grade Sodium sulfite and photo grade.

    Iron is the only area with lower levels for photo grade then food grade. What are the odds that the photo grade is just stuff not good enough for food grade? It's not like the food grade has to have more iron. Just that it's allowed to have more. Those standards are the bare min that the product will conform to.

    I guess my point is photography is just one more industrial process.
  12. You might just try sending the company an email. While at the grocery store I noticed Arm & Hammer Super Washing Soda for $3.00 for a 55 0z. box. The sodium carbonate I usually buy is called Spa Time and costs $6.00 for 18 oz. It says 100% sodium carbonate on the container. I emailed the Arm & Hammer co. and asked them the content of their washing soda, explaining my intended use (one of Pat Gainer's formulas) and they emailed me back the following day telling me that their product is 100% pure sodium carbonate. I don't know how pure anything can really be, but Arm & Hammer's indication was that they don't put anything else in it, so I tried it. Works like the Spa Time stuff as far as I can tell, and it's easier to get too.

  13. I buy chemicals from a recognised supplier of photographic chemicals (Rayco Chemicals of Barnsley, Yorkshire). It's not worth the risk to buy chemicals of unknown assay. Years ago I used to buy chemicals from a company called Analytical Supplies. The biggest unknown in mixing one's own brews is the water supply.
  14. I don't have any experience in the chemical business, but I wouldn't be surprised at all if
    the biggest difference between the grades was what label they slapped on the container.
    As somebody else already mentioned, chemicals are purer today than they were years ago,
    so I could see the company having orders for technical grade, food grade, and photo
    grade just grabbing 3 different containers off the shelf (or from the warehouse, etc) and
    putting the proper labels (as per the order) on each.

  15. Rowland, It is worth mixing with the purer Photograde. I speak from
    experience. I did some testing of Neofin Blue recipe as well as a few others
    for effects. The intial tests were very good but when it came time to go out and
    field test, the developers had set for a week and although the development
    was the same, I got some chemical burns on the film. Truth be told, there was
    a slight sediment of what I'm not sure of (chemicals) and I tried to decant as
    slow as possible. At the time, I was using Arm and Hammer Washing Soda
    and 20 Mule Team Borax. The recipes that I had said that B/W didn't need
    photograde but after doing the same tests later that year (well, it was in the
    spring at around the same time the first tests were done...) with photograde, I
    had no problems at all. It's great to experiment but don't let it get to the point of
    needlessly chasing your tail! Prints you can reprint but negatives are
  16. The question is not what is inert for a particular use, but what will the regulating body allow to be stated as inert. The hTh pHPlus says 98% sodium carbonate, 2% inert ingredients. If sand were present, it would not stay in suspension, and if it were fine enough to be colloidal, it probably wouldn't hurt the film. We won't count water, which is the most likely, seeing that anhydrous carbonate tends to become monohydrated at the slightest provocation.

    Chloride might be counted as inert, but I doubt that bromide would be. We can't even get bromide in Bromo Seltzer anymore. I tried adding sodium chloride in copious amounts to D-23 and Rodinal with little effect. Of course, bromide and especially iodide would be a different story, but I have had enough experience with pHPlus to know it is not there in significant amounts.

    You can dissolve pHPlus to saturation in distilled water and not see any cloudiness or precipitation (other than due to cooling).

    I have ordered a 17 pound pail of anhydrous sodium carbonate from for $15.98 + shipping. They always send an assay sheet with their chemicals, so I will let you know how pure it is. If it suits your scruples, I think that is a good price. It's even cheaper if you buy a bigger pail. They also have potassium carbonate and a number of other chemicals we strange people like to have around.
  17. >> Iron is the only area with lower levels for photo grade then food grade. <<

    Robert, it's misleading to say this!

    On the web site you formerly listed,, I see five other items listed where General Chemical's photograde HAS specs listed, but the food grade does not. So the photographic grade is more stringent in these areas. Although strictly speaking your statement is also correct since food grade does not have ANY level listed.

    These items are: Sodium Sulfate, Alkalinity (as Na2CO3), Insoluable matter (Ca, Mg, NH, pHppt), Thiosulfate (S2O3), and Water Insolubles.

    There seems to be a lot a naivety about the chemical business. I think I'm starting to see what's going on here from Michael Schiller's post about the company "...grabbing 3 different containers off the shelf (or from the warehouse, etc) and putting the proper labels (as per the order) on each.". Industrial use would typically have forklifts loading your order. When you use industrial quantities, you are in a position to get ANSI/ISO photograde materials. If you are buying a quantity that you can carry in your arms, you probably don't have the ability to demand ANSI\ISO photograde.

    I can see that hobbyist suppliers might purchase photograde, then repackage smaller quantities for resale. Alternatively, they might buy a certain grade from a supplier, then do their own abbreviated photographic tests, then repackage it as photograde; this would not mean it meets ANSI\ISO, just that this supplier calls it photograde.
  18. A couple more comments; I'm not saying it's a bad idea for someone to use other grades; it's a choice sort of based on whether you have more time or money on your hands, or whether you experiment for fun. If you DO experiment with non-photograde, any problems will be entirely yours; the chemical manufacturer will probably not help. If you do commercial processing, I don't think you should take chances here.

    One more item, I believe that Patrick Gainer is a very smart, sensible and practival fellow, and one can see that he is not using substitute chemicals blindly. In his last post on hTh pHplus, one can see that he has evaluated the possible effect of chloride (at least in D23 and Rodinal), bromide and iodide (he's already pretty sure there's not significant amounts) and he has (possibly unknowingly) approximated one of the typical ANSI photograde tests by examining a strong solution for cloudiness or precipitation. (Patrick, let me know if you're interested in any specific ANSI details.)

    Ok, last item; Ron (Rowland) is also a very smart fellow, but one who has some pretty extensive industry experience in doing well controlled testing. As such, he's probably seen all sorts of unanticipated interactions come up, and probably prefers to minimize these in his personal processing. I tend to take this viewpoint myself. My own substantial industry experience is from the standpoint of a high volume chemical/film/paper user, so I have also seen quite a few unexpected problems. And although I think these are often fun to troubleshoot, I don't currently care to have them coming up in my personal, low volume work.
  19. Well, yes, I would like to know what the regulations are about stating active and inert ingredients. I doubt that a supplier can be held free of blame if a statement of inert ingredients is taken literally by someone using the product for other than the purpose intended by its manufacturer or distributor, only to find that there are ingredients that are not absolutely inert.

    My well water has ingredients that make it not so good for photo use when I use carbonate, but it is in fact better for drinking than pure water. People who drink this kind of water have fewer heart problems. I had an analysis done once, and a good many active ingredients were found that were not harmful to one who drinks it, but they would not pass as inert ingredients. I think something that is labelled "inert" should be about as inert as silica or nitrogen or helium, or at least only present in trace amounts. I can't think of any of the alkali metal compounds that could be considered as inert in a swimming pool or hot tub. If sodium or potassium bromide or iodide could be called "inert", then sodium carbonate can also. Harmless, maybe. We certainly can swim in sea water, more comfortably than in chlorinated water, but most of us would agree that the chlorine is the lesser of two evils. If the solids extracted from sea water were as much as two pwercent bromide, .... I'm rambling.
  20. Hi Patrick. Sorry, I don't actually have Sodium carbonate specs available; however here is some POTASSIUM carbonate data, probably limits are very similar.

    >> what the regulations are about stating active and inert ingredients <<

    Well, the ANSI specs don't refer to things as such; rather they simply say what certain limits should be and explicitly describe a test method. I'll practice my typing a little with a few excerpts. (no good way to copy except maybe some digital camera snapshots.) If you see anything funny, ask as it may be a typo!

    ANSI PH4.229-1987
    ... for photography (chemicals) - potassium carbonate, anhydrous and sesquihydrate


    (This standard is one of a series that establishes criteria of purity for chemicals used in processing photographic materials.
    Although the ultimate criterion for suitability of a photographic-grade chemical is its successful performance in an appropriate use test, the shorter, more economical tests described in this standard are generally adequate. ...

    3. Summary of Requirements

    Assay (K2CO3): 98.0% (m/m) min

    Assay (K2CO3)-1.5 H2): 98.0%-102.0% (m/m) min

    Appearance of solution: To pass test

    Volatile matter in K2CO3 at 150 deg C: 2.0% (m/m) max

    Volatile matter in K2CO3-1.5 H2O at 150 deg C: No requirement

    Bicarbonate (HCO3): 0.25% (m/m) max

    Free Alkali (as KOH): 1.0% (m/m) max

    Heavy Metals (as Pb): 0.001% (m/m) max

    Iron (Fe): 0.001% (m/m) max

    Halides (as Cl): 0.06% (m/m) max

    Reaction to Ammoniacal Silver Nitrate: To pass test

    Now, some BRIEF description of a couple of the tests:

    The assay: Basically, take about 3.0 grams of the sample and weigh to the nearest 0.0001 gram, and dissolve in about 50 ml water. Using methyl orange indicator, it's titrated with a certified standard 1 M HCl solution to a yellow to red color change. [Warning to the non-trained person: the ANSI standard contains DANGER warnings with respect to the HCl, so don't try this unless you're sure you know what you're doing]. The calculations are: [(ml HCl)(M)(factor)]/grams_of_sample = % assay; for anhydrous, factor is 6.91; for the sesquihydrate, factor is 8.26.

    For the halides: Basically, make a reference solution of NaCL in water; I didn't read this carefully or check calcs, but it looks like they are ultimately making a reference solution to duplicate the spec limit. Then, solutions of both the reference and the test chemical are slightly acidified with Nitric acid, then finally a bit of a silver nitrate solution is added. The two solutions are compared (Nessler color comparison tubes); Any turbidity in the sample shall not exceed that of the halide standard solution.

    These general kinds of methods are typical for many of the ANSI tests.

    Other chemicals have somewhat different limits. For example, KBr has specific limits for Chloride and iodide as 0.2% max and 0.01% max, respectively.

    I don't know for sure how many ANSI photo chemical standards there are, but it definitely exceeds 50.
  21. Guys;

    Here are some practical answers to some of your comments and questions.

    D76 has no halide in it. Using carbonate with a halide impurity introduces halide into the developer. As Patrick says, this would not appear to be a problem. Lets look more closely though.

    A hypothetical Selectol Soft uses a 5 g of a 10% solution of NaBr in one liter. That would be about 0.5 g/l of NaBr. Lets say it also uses about 50 g/l NaCO3. If 2% of that were bromide, that is 1 g/l of NaBr added to the developer. That tripled the amount of NaBr in the formula.

    If that is the only change, then you see a speed loss and perhaps a contrast increase. If you are using a pure chloride emulsion paper, it could be a disaster.

    Now, assume that the impurity is NaCl and you are using either a film or a paper with Bromide emulsions. Not a problem. Change to a chloride emulsion and you see strong retaining action.

    At the worst, if the impurity is Calcium Carbonate, you see turbidity and sludge and you can get this into the emulsion.

    I hate to disagree with Patrick, but anything that is in suspension can get into the emulsion, in the interstices of the swollen gelatin. Especially if the particles are fine which would be the case in something suspended or in fine sand particles for example.

    If this dries down, it forms a whiteish filmy scum throughout the film, and can affect the printed image. It is very hard to get out.

    This is why so many commercial formulas include antisludging chemicals such as calgon and quadrofos. The calcium and heavy metal sludges can adversely affect your negatives and prints. The finely divided particles in suspension can get into the gelatin.

    Note that I said CAN, not WILL. I don't say you will have a problem. I'm saying that I don't want to chance it personally after I have spent hours shooting pictures, mixing chemicals, and developing the negatives...etc..

    I want to enjoy, not worry and I just wanted to share some of my concerns.

    Ron Mowrey
  22. I missed the connection between D-76, which has no carbonate, and impure carbonate. Probably a typo.

    Still, for a chemical meant to be used in swimming pools and spas I don't think any soluble bromide could be considered inert or labelled as such, certainly not 2%.

    Different people worry about different things, and that's their privilege, and sometimes their duty. Such worries about foodstuffs are a religious obligation for many. If I had ever had any problem with a developer that could be attributed to impure carbonate, I would have spread the word. If I find, on the other hand, that a cheaper grade of a chemical is photographically as good and reliable as a more expensive grade, I will also spread that word. I make no money from these recommendations. I try to keep from spending any more of my retirement annuity than I must in order to enjoy the hobbies I have and learn something in the process.

    I'm certain Rowland Mowrey has lower expectation of poor results by using highest quality materials. I only question whether the extra cost is the only guarantee of higher quality, or if there is an assay available or better yet, that we could perform, to back up the claims.

    If I could do a simple test to show if the contaminants that Ron worries about are truly present in my cheap stuff and not present in the expensive stuff, I would be convinced that it would be worth the money. Describing the worst case scenario is not going to convince me, because I have never seen that scenario unfold.
  23. Patrick;

    What you say is correct. There very well may be a low probability of bad things happening in B&W film and paper processing. What started me on this was the series of people with minor problems with scratch mix developers posted here, and the observations that pool chemicals are not photo grade.

    I didn't mean anything specific, as D76 is just a hypothetical example, being a Kodalk developer. I just picked it out due to it being no halide I couldn't think of a no bromide developer off the top of my head, with carbonate. It was my error in not being more detailed in my post. Sorry.

    Dektol or Selectol scratch mix examples above are more to the point being aimed at papers and therefore sensitive to any halide impurities, and being carbonate developers.

    I do worry about suspended matter in my film developers as I have seen it ruin otherwise good negatives. This should be avoided at all costs, as colloidal solid matter is anathema to films whatever their chemical nature is. They fill intersices in the gelatin, when swollen, and are usually impossible to remove. So, in that one point I seem to disagree with you. This point, regarding suspended matter should not be lost among the other comments here.

    I am quality conscious, due to my past training and as I mix a lot of color processing chemistry from scratch, and a tiny error there can make a big mess and cost a lot of money. I too am retired Patrick, but to me, the film and labor in taking pictures and printing them are more valuable. In my limited time to devote to photography, I want it to come out right the first time.

    Today, for example, I spent an hour loading up 10 sheets of my stash of 4x5 Super xx, and my wife and I spend 2 hours trekking through a wild bird preserve observing swan, ducks, and geese and their families and taking pictures. Tonight, I want to process them and have them turn out perfectly. I don't want to lose them as my stock of Super xx is limited and I can't keep driving out to the field and hiking to the site... etc.

    The question asked above was, which do you have more of, time or money? I would add, which is more precious to you, time or money? I find that my time is worth more to me than money as I will probably run out of time before my pension plan runs out of money (ie, the pension stops when I stop). So, I don't want to have to keep retaking pictures due to possible darkroom errors. I want reliable darkroom chemistry.


    Ron Mowrey
  24. Ron, questions-

    What wild bird area did you visit?

    When you referred to chloride emulsions, did you have any specific product in mind?

  25. Conrad;

    We were at Braddock Bay State Fish & Wildlife Management Area. There was a specific part we visited, but the name escapes me. We have quite a few around here.

    As for chloride and chlorobromide emulsions, most papers are either chloride or chlorobromide. Addition of bromide to a developer being used for a chloride paper will restrain it heavily, adding chloride will restrain it mildly, and iodide may desensitize it completely, IDK, not having done that latter addition. Adding chloride to a developer for bromide emulsions may have no effect at all or it may increase contrast. Adding bromide will restrain a bromide slightly, and adding iodide will restrain or desensitize it heavily. Chlorobromide emulsions fall in between.

    Ron Mowrey
  26. Ron

    You've rised an interesting point.

    Sometime ago, I've added sodium chloride to FX-37 1+5 to develop PX. To my surprise, negs were densier than before the addition (technical NaCl).
  27. Jorge;

    Sodium Chloride is a silver halide solvent and would act as such in a developer. It could increase contrast of a fine grained bromoiodide emulsion if added at the right strength.

    If you added enough sodium sulfite to a chloride paper developer, you would get an image while fixing the paper at the same time. For example, D76 used as a developer for a chloride paper, develops an image and fixes out the remaining silver halide.

    I don't recommend that.

    The image is not very good, and the fixing isn't very good, but they both take place making D76 a weak monobath for chloride papers.

    I've done it much to my dismay.

    Ron Mowrey
  28. Thanks Ron. I was curious about the emulsions because I was led to believe that almost no pure chloride emulsions were still made (maybe Azo?), and that everything was chlorbromide. I've heard of Braddock, but have to check a map for the location. I'm over in Canandaigua and often visit Hi Tor (sp?), Grimes Glen in Naples, and whatever else I can find on this side of Rochester.
  29. Conrad;

    I love Grimes Glen and Clark Gulley. There are a few more in Naples, 4 total to be specific, and I often go there. Also I go over to Breakneck Gorge on Seneca lake and Rock Creek on Seneca lake (with permission of the owner). There is also a very large gorge on the grounds of Windswept farm that I have climbed through with the permission of the owner. Letchworth and Stoneybrook are also very nice if you go off the beaten path or out of season.

    I love to fossil hunt at Kashong as well.

    Give me a call sometime if you would like to join me. I would also like to learn about some of your favorite spots.

    As for chloride emulsions, there are quite a few out there surprisingly enough. But many are chlorobromides with varying degrees of chloride.

    Since NaCl is a silver halide solvent and a development restrainer both, it is difficult to decide how to use it in a given developer with any of those emulsions. Sulfite is a preservative and a silver halide solvent, and it has to be well balanced.

    Developer design is a very exacting science as well as an art.


    Ron Mowrey
  30. Ron,

    I understand your viewpoint, but I still don't know how you know that the carbonate you buy is any purer for photo purposes than the hTh brand of pHPlus. How do you know that someone isn't taking carbonate out of the pHPlus barrel and selling it for photo grade, which it might in fact be anyway? Can you test it for photographically active but legally inert ingredients? If there is a simple test, the rest of us would like to know how to do it.

    If I were going to be worrying about the purity of the cheap stuff, I would worry as much or more about the purity of the expensive stuff. How do I know I will not wind up paying more for the same disaster? Is it claimed to be 100.00% pure?

    That is why I would like to know the legal meaning of such terms as "inert" and "100%" and so on. Until then, I will do my testing the best way I know how.

    Sodium chloride is not a concern in film developers. In my tests for my P.T. article "Salt to Taste" I tried amounts as great as 100 grams per liter of D-23 and Rodinal with very little effect on film speed or development time. 4 grams of sodium ascorbate per liter of Rodinal had more effect on grain and resolution than 100 grams of pure sodium chloride.

    Do you have a reason for believing that the halides are likely impurities in the manufacture of sodium or potassium carbonate, and that they would be considered as inert ingredients?
  31. Patrick;

    As I stated above, I have no evidence one way or another.

    I merely made an observation that I thought others needed to be aware of in light of certain posts regarding difficulties with hand mixed developers and my own observation from reading the labels of several boxes of sodium carbonate at pool stores.

    I have no evidence that a chemical source is better or worse than any other source, however other posts in this thread do indicate that there are reasons to believe that photograde does have some meaning. My own experience has also taught me that same lesson.

    I made an observation about suspended solids in developers which is a real concern to me, as I have seen it ruin photographs. That is the only major point that I have made that I have raised as a concrete issue based on personal observation, and you have disagreed with it.

    That observation is a real concern and has gotten lost in the arguments over the purity of different chemicals.

    As for the impurities themselves, as little as 0.1 g/l of NaCl added to a developer for AgCl paper emulsions causes a significant speed change and contrast change. I don't have the time, money or inclination to make every possible test for every possible paper. I just want to let people know that their might possibly be a problem with purity levels and depending on the product they are using it could blindside them.

    Getting back to suspended matter, there is certainly a possible problem with it if you see any in your developer. So, if the inert material is not soluable and remains in suspension, I recommend not using it for the development of critical fims. Your further thoughs on this would be useful.

    Your experiment using sodium ascorbate is interesting. In alkaline solution, it oxidizes rapidly, and can oxidize on the shelf. Just like any reducing agent in our atmosphere. It then ends up with a fair amount of 'so called' intert material in it.

    When I ran experiments with developing agents in solution, they were analyzed before and after use for the developing agent in question, and all samples were stored under a nitrogen atmosphere. They were compared with samples left out in the air. It was always a surprise to me to see how much reductant was 'gone' due to aerial oxidation in samples in the bottle on the shelf as well as in the mixed solutions.

    I myself ran a developer experiment, and half way through, found that the sample of one chemical was about 50% pure or less to start with. Therefore, I had about 1/2 of the chemical that was useful. It worked wonderfully though, but I later found that the impurity was the better reagent than the chemical I thought I was testing. I had them make me more of the 'pure' chemical and it wouldn't work properly, so I got discouraged and let it sit around, then retested it and lo and behold, it worked better. That is how we found the correct chemical additive for our future experiments.

    There is a lesson to be learned here Patrick that experiments, even if repeatable, may not be repeatable by someone else or you may not be able to repeat your own results if tested with new chemicals. I am agonizing with some of that right now myself, or I wouldn't have started this kind of thread.

    Even if you think that you have repeated the results, what quantitative result do you have to back up the first experiment and the repeat? This is a question that I ask myself. I try and repeat every experiment fresh and after a few days. I track my results over time to gain a feeling for repeatability.

    So, here it is then. If the carbonate is varying between 98% and 100% pure and the impurity is truly harmless, then you have a 2% variation in alkalinity at the very least from batch to batch. It is up to the user to determine if that variation in total alkalinity is of concern. If the inert material is finely suspended matter, then I contend that it will probably hurt images on film.

    To be clear on my position here, I believe that truly soluable inert materials are harmless. If they are truly photographically inactive.

    I also believe that developers can vary by as much as 2% - 5% with no significant problem for the average person. Some people may even be able to tolerate a 10% error or deviation. Professional or critical users will probably see a deviation if it is 2% or less.

    That last paragraph is an opinion. The comment on suspended matter is not opinion.


    Ron Mowrey
  32. Does make one wonder about certain glycin developers like that Harvey's 777 formula, Dassonville D-3 autotoning, and even Ansco 130. They can all be murkey suspensions and give the uninitiated little confidence. For paper it probably doesn't matter, but I filter all my film developers. I find filtering through clean cotton works well, followed by a couple days settling. Filter paper is more effective, but the slow dribble can't be good for oxidation. I suppose if I were really fussy I'd set up a vacuum filtration system.

    Patrick gets to the heart of my skeptical thoughts- we have no way of knowing the purity of pretty much anything supplied to us. I have enough experience in industry to know that many, if not most, companies don't operate to the standards we might like to think. ISO 9000 is no guarantee, in fact most companies I've dealt with seem to work to a lower but consistant standard after their ISO certs. Probably too busy doing paperwork to worry much about the products. Receiving a guaranteed assay with every bottle would be nice, but these days I'm just happy when a company will sell something to a private individual. I long for the idyllic days of carefully purified photo chemicals described in my old Mallinckrodt catalogs! As a practical matter, I use the pool and supermarket products, but am always on the lookout for unusual behavior or appearance. I also keep a small stock of the same items from Photographer's Formulary, so at least if I have a problem, I can compare. So far, knock on wood, I ain't been burned.
  33. Well, I use the settling method.

    Fitration is slow and does increase oxidation.

    I usually get no suspended material in prepared formulas, and they dissolve faster. Hand mixes have more sediment and are harder to dissolve. That is personal experience and industrial experience speaking.

    But, I can't always buy what I want prepared. So, I have to hand mix.

    I store some of my critical solutions under nitrogen here. I have a tank of N2 and a distribution line scavenged from an old nitrogen burst setup. It seems to help a lot.


    Did you read the above about the other hiking opportunities? I have a web site to refer you to.


    Ron Mowrey
  34. Sorry to get in on this so late, but-

    Patrick wrote, "...I still don't know how you know that the carbonate you buy is any purer for photo purposes than the hTh brand of pHPlus. How do you know that someone isn't taking carbonate out of the pHPlus barrel and selling it for photo grade, which it might in fact be anyway? Can you test it for photographically active but legally inert ingredients? If there is a simple test, the rest of us would like to know how to do it."

    Patrick, it's not a matter of one being any purer than the other, it is a matter of meeting the specifications that have been decided for any particular use.

    The only assurance you can have that your substitute materials are equivalent to the photograde or even reagent grade chemicals that are used in making photochemistry is to actually perform (or have someone perform) the tests that are used to certify any particular chemical for the intended purpose. There was already a listing above of the requirements for photograde sodium carbonate. Those tests are generally pretty simple in nature and could really be performed by someone with just a few simple pieces of lab equipment. Simple things like a balance, a buret, and some Nessler tubes - that's it. (Nessler tubes are just glass tubes that are about 15 inches long and 1 inch in diameter have volume lines on the side and caps. They are intended to be used to compare turbitiy or color intensity by looking from the top into the bottom, through the center of the tube. This is how things in chemistry labs were measured before the invention of spectrophotometers.)

    As you saw, the tests for the carbonate were really simple, such as dissolve a known amount in water and observe for cloudiness, acidify a solution of known concentration and add some reagents and observe for cloudiness and compare with a standard, titrate a known solution with a known titrant, dry at a specified temperatuer and determine the weight loss... These are tests that you could easily do, and most others on this board as well if they really wanted.

    As far as your question about what is inert - the answer to that completely lies in the intended purpose for the chemical. Something that is designed for swimming pools (as an example) is most likely going to have a different set of specifications than the photo grade stuff. As Ron says, bromide and chloride are a concern for photochemicals, and as you see above, there was the Nessler test to measure the amount of halogens by adding silver nitrate to make a precipitate with any halogens (chloride, bromide, iodide) present in the carbonate. In a photograde sodium carbonate, halogens ARE NOT INERT. In your pool grade chemicals, halogens ARE INERT, as they have no detrimental effect on pool chemistry and are probably not tested for because of that. It is the intended purpose that determines what is inert.

    So by buying photograde carbonate, you have some assurance that the reagent has been QCed to meet the specifications required for photography grade chemicals. Buying pool grade, you do not.

    Now as you have found out, for your purposes, pool grade has been of sufficient quality that you have obtained acceptable results. That's great. And if you want some more assurance, you could easily do some of the QC testing to see if your substitute sources meet the stated photo chemicals specifications. Many of those tests are really easy to do, as I mentioned above. And you may find that they in fact do met the specifications, but you can't be certain without doing the tests.

    And speaking of if both chemicals are coming out fo the same initial barrel, that is certainly possible, but the certification you get when buying a particular grade means that someone has taken some of the material from that barrel and certified it. Some things may pass with no extra work done, and other things may need some significant purification steps involved.

    And since we are talking about sodium carbonate, next time you are in Trona, CA, check out the soda ash plant there, or if in Moab, go to Dead Horse Point and look down on the Potash plant which is very similar. While Sodium Carbonate (which is also called soda ash when in the anhydrous form) can be made synthetically, much of it is made by mining it. It can be found in evaporite lakes like the one at Trona, or buried deposits similar to the one at Potash, UT (which produces the potashium equivalent, potash). The ore is dissolved and if underground, pumped to the surface, and the saturated solutions are then put into evaporating ponds that are open to the environment and subject to any dust conditions. The solutions dry by evaporation, and as that happens, different chemicals such as chorides or sulfates will drop out of solution at different times. The liquid can be pumped out and the precipitated left behind and recovered. Ultimately the solution is dried and the bulk of the solid materials are collected. This evaporatite is then heated to remove water to make the soda ash. This is then shipped as the bulk chemical that may be refined further for other uses or used as is. Some of the chemicals that are recovered from the evaporation process are sodium carbonate, sodium bicarbonate, sodium chromates, sodium phosphates, and sodium silcates. Limestone is often recovered as well. Much of the soda ash produced itself is used directly in the manufacture of glass and detergents.

    So after all that, I guess I'm saying that while substitute chemcials may be just fine for photo grade work, you can really tell without looking at the specifications for the different grade.

    Using the pool grade sodium carbonate as an example, I suspect that what you are getting there is industrial grade soda ash and it has no more refining than simply letting the dissolved ore that has been pumped from the ground go through a series of evaporation ponds that are open to the air, and then scooped up by an earth mover or front-loader and then shipped off to eventually end up in your developer.

    Without testing, you have no assurances that your chemicals are sufficiently pure for your intended purposes.
  35. Actually, I was thinking about what tolerable impurities would be present in pool-grade sodium carbonate. While chloride is certainly a potential contaminant of mined sodium carbonate (as Kirk described) I think it is also likely present in prepared sodium carbonate... My copy of Mellor's Inorganic Chemistry states that "nowadays" (ie. the 1950s) it is produced electrolytically by electrolysing a solution of sodium chloride to produce an aqueous hydroxide solution and then forcing CO2 through it to crash out the carbonate. I don't know if this is still the major synthetic method for sodium carbonate production.

    For pool purposes, I would think that while chlorides would be acceptable contaminants in sodium carbonate (the pool contains chlorine water, after all) bromides and iodides would be no good. Theoretically the hypochlorite in pool water could liberate free bromine or iodine from the salts. While bromine would probably be okay in the pool (some pools use bromine as a disinfectant IIRC) I think the iodine would be unacceptable.

  36. All halides are to some extent bad, if uncontrolled in developers.

    All halides are, for all practical purposes, inert in a swimming pool, even iodide. (after all, iodine is a good disinfectant and is used as such)

    Patrick says that he saw no effect of adding massive quantities of NaCl to a film developer. May be so, but I wonder what MTF or RMSG looked like. Or, I wonder what the toe of the film looked like and what the pushability was in that developer. Something changed and just because a human eyeball couldn't see it didn't mean it wasn't there. It may have been bad or good. IDK at all. On that basis, he seems to dismiss the effect of halide contaminants on film sensitometry.

    Until I see some quantitative data to support that statement, I am sceptical.

    The comments I made about suspended matter have been largely ignored here. That is another concern.

    As for mined vs synthesized sodium carbonate, it would be my opinion that industrial grade carbonate would be better mined, and reagent or analytical grade would be better synthesized. Just an off the top of my head reaction due to the expected costs of purification of the ore to analytical grade vs making the material from pure starting materials. IDK for sure.

    Ron Mowrey
  37. Jordan - The other common commercial process is the Solvay process [for Ernest Solvay] for the manufacture of sodium carbonate (washing soda/soda ash). It's kind of similar to what you describe. The Solvay process takes ammonia (a strong base) and carbon dioxide and passes them into a saturated sodium chloride solution to form soluble ammonium hydrogen carbonate, which then reacts with the sodium chloride to form soluble ammonium chloride and a precipitate of sodium hydrogen carbonate (sodium bicarbonate) - if the temperature is maintained below 15?C. The sodium hydrogen carbonate is then filtered off and heated to produce sodium carbonate.

    The Solvay process was the main source of soda ash until the Wyoming trona (the mineral, not the town) deposits were discovered. However, it is more expensive than mining natural sodium carbonate deposits, so I think now the bulk of commercial soda ash is mined. In addition, the waste products of the Solvay process are harmful to the environment and could cause serious waste management problems.

    Iodine in a pool would not be detrimental, as Ron says, it is a fine disinfectant as well.

    Ron, I was trying to address your concerns about suspended matter - it certainly is a concern. First off, the trona deposited in the bottom of a basin millions of years ago and then were covered with thousands of feet of of earth (Wyoming deposits), or dried up in the last several thousand years from inlands lakes and have been exposed to the elements (Trona, CA). There's a lot of dirt involved in those two processes. And it will certainly be introduced in the mining process, as well as in the evaporating steps of the solutions. I've been past Trona,CA - it is out at the north end of the Mojave Desert, a pretty dusty place. The Potash mine near Moab is in a dusty environment as well. Anywhere you can refine minerals that have been pumped in solution out of the earth and dring them in open ponds on the surface is going to have to be a pretty dry spot, and most likely dusty.

    As to synthetic vs. mined soda ash as the starting point, it may be that most of the refined sodium carbonate we get starts out as mined. The soda ash industry figures I was looking at says that the #2 use of soda ash is in making the sodium compounds I mentioned above (which included sodium carbonate). It was right in betweeen making sode-lime glass and detergents. SO it appears that most of the sodium carbonate does start out as mined soda ash. Remember, it probably costs more to make the "pure" reagents needed to make the synthetic sodium carbonate than it does to more highly refine the mined soda ash into higher grade sodium carbonate. The process to more highly refine the soda ash may only involve recrystallization, under cleaner conditions than the middle of the desert...

    So that's why the specification for the photograde carbonate presented above had the test to check the turbidity of a solution of carbonate at a known concentration. That test has got to be the easiest of all the tests in the specification to do. I think it would be intersting for Patrick to do some of those tests as it may sway some readers to his side of the issue. It could certainly ease some of your concerns if the materials came up to meeting the specifications.

  38. Ron,

    I respect your opinions, but fail to see the logic. 2% change in sodium carbonate concentration will not make 2% difference in pH, and if it did, how much difference will it make if pH is 9.8 or 10.2 instead of 10.0? There is more error than that in controlling developing time and temperature.There is much more tolerance than that in printing.

    You might try reading my article in P. T. entitled "Salt to Taste" before you accuse me of anecdotal reporting.
    How do I know my results are consistent? Most of my experiments involve H&D curves. I have in fact found differences in density between two theoretically identically exposed adjacent frames of 35 mm film developed at the same time in the same tank of developer. I am still trying to find out what caused these differences, but there is no way I can blame the carbonate because I did not use carbonate, nor did I use borax. The alkali was triethanolamine, wnich may have had impurities. If so, they were not of the sort that could result in uneven development. The solution was homogeneous and perfectly clear. Most probably, the difference between frames was due to slight variations in shutter speed from one frame to the next.

    Many photographers recommend diluting HC110 directly from the syrup. Dilution B then takes 15.625 ml to make 500 ml of working solution. Must I worry if I only get 15.3125 ml or if I overdose to 15.9375? Will I see the difference if I make 510 l of solution or 490 instead of 500? These are 2% differences. You are saying that mismeasuring 15.625 ml by +/- 0.03 ml will make a difference that may ruin a picture. Sorry, I don't believe it.The tolerance in film manufacture is 1/3 f-stop in film speed. Who knows what the tolerance may be in the manufacture of HC110 and in the tolerances of its components?

    If you have not the wherewithal to do a chemical analysis of everything you buy for the darkroom, you can do a photographic test before you do the negative that will make or break your reputation or your heart. If you mix your own developers, you may stand a chance of getting more than a few liters of consistent developer out of a single batch of each ingredient. It doesn't make any difference where you got the ingredients if they produce the desired result. If they do not, by all means use a different source, but be sure to test it as well.

    If I buy sodium carbonate for 65 cents a pound and it does the same job as that I was buying for $5 a pound, tell me again why I should not use the cheaper one.

    As to sodium ascorbate, yes, it can oxidize quite readilly, but not if it is kept truly dry. I use ascorbic acid and when I want the ascorbate, I neutralize it with sodium bicarbonate or sodium hydroxide. The acid keeps much longer as dry powder. A way to keep it even longer is to keep it in a non-aqueous stock solution, for which propylene glycol is convenient.
  39. Kirk, Mellor seemed to suggest that the Solvay process had been supplanted by the electrolytic process by his time (I don't have it in front of me now so I'll have to check later) due to the availability of cheap electric power. I understand that iodine is a good disinfectant but it also has a tendency to stain things. Probably not a problem at concentrations that would be introduced by oxidation of adventitious iodide.

    I looked through the MSDSes of three "pH Plus" compounds available on-line, and the stated Na2CO3 purities were 95%, >99.8%, and 100%. MSDSes are not necessarily correct in terms of these kinds of numbers, but it does seem that there is brand-to-brand variation.

    I would agree that insoluble particulates would certainly be a concern for many applications.
  40. Patrick;

    I did not say a 2% variation in carbonate would cause pH to vary 2%. I said that a 2% variation would cause a 2% variation in alkalinity (total alkalinity is a measure of buffering power).

    Since, during rapid development, the pH of an emulsion can become the home for a lot of released protons, a good buffer is required in high and repeatable concentration for the solution to work evenly. A variation of 2% can cause quite a distinct color shift in color photographic materials just by changing the development rate of the layers with respect to one another by the change in buffering capacity. Anyone out there care to calculate the local pH in a 100 micron thick emulsion with 1 g/meter square of silver developing to 50% completion? You will be amazed at the result. But don't worry, if you throw in diffusion of the alkali, it works out ok in the end.

    I can have 2 developers at the same pH by measurement, and one will yield totally different results than another due to buffer capacity.

    In the final analysis, I did say that a 2% - 5% variation would probably not be serious for most people. I would add here that -5% in one batch and +5% with another batch might be a bit extreme though.

    I also said that macroscopic examination may not show differeces, (densitometry being one macroscopic measurement), and went on to suggest that perhaps MTF and RMSG should be examined to be fully revealing of how well and how consistant a developer is.

    That is perhaps why some commercial developers appear to us to be so expensive. The mfgr has done a lot of tests beyond just densitometry.

    So, Patrick, I believe that you have used normal testing procedures to verify your developers (densitometry and pictures). Your work would not have been published if you had not run this type of test. Having run tests exhaustively for the pre-release of EK products, I know how costly and extensive they are. I also know that the average user could not possibly have run all of the experiments due to the instrumentation involved and their cost let alone the time involved.

    And, I point out again that you have not addressed the issue of suspended solids in developers. Your opinion would be useful on this beyond dismissing it as a non-problem.

    Remember, I only started this thread as a commentary on an observation about using pool supplies, and soliciting input, and what further caused my post here is the number of complaints about bad or non-repeatable results from hand mixed developers.

    Ron Mowrey
  41. Guys;

    Here is an afterthought I had after posting something in another thread about C41. It is worth while repeating here.

    I was doing the original work on Ektacolor 30/37 paper but before that, I tried to come up with a new developer for the current product using a new development time and temperature combination to see how far it could be pushed.

    I had mixed up 12 color developers that gave exactly the same sensitometry with one batch of paper under a variety of processing times and temperatures. Then I reran the test with a dozen or so other batches of paper, and the production developer gave identical results to the original emulsion, but each of the other batches of paper gave different results in each of the other developers.

    I learned an important lesson from this. The film or paper is designed to fit through a given narrow window of development. It is checked within that window. Going outside of the window may work for one or more emulsions, but may not work for everything.

    Ron Mowrey
  42. If you want to talk about color developers, leave me out. I don't do color printing. I have upon occasion developed Ektrachrome, but not in several years.

    I also want to enjoy my photography, but if I must worry about infinitesimals, I won't. I am not going to go out of my way to convert anyone to my viewpoint on many things. If anyone wants to do experiments to prove I am wrong in any matter that makes a difference, let it be so.

    Where solid matter is concerned, if it is too lerge to fit into the interstices of the gelatin, I won't worry about it. If it bothers me, I will filter it out. If it's small enough to form a colloidal suspension, maybe I will test to see if it is damaging. You said you had evidence that it could be, but didn't say what the evidence was. As I said in one of these posts, I have seen suspensions of calcium and/or magnesium carbonate due to the reaction of sodium carbonate and my well water. These are not colloidal in that they eventually settle out or can be filtered out. There is no connection to the purity of the carbonate because such suspensions are inevitable when you use carbonate in hard water unless you use a sequesterant. I don't like to do that when I am working on something that I mean to publish for obvious reasons.
    I still have not found a meaningful interpretaion of the 2% inert ingredients. Absolutely pure monohydrated sodium carbonate could be said to have 6% inert ingredients. Any degree of hydration less than 6% could be anhydrous with a small percentage of inert ingredients. I will see if I can get a more definitive answer from hTh.
  43. Patrick;

    Unless a developer is mixed with distilled water, it is probably going to have particulate matter in it either from the municipal supply in the form of insoluble granules of matter or the presence of 'hard' ions such as calcium and etc. that precipitate during mixing of the developer.

    In addition, many European water supplies use Ozonolysis for reducing bacteria count, while American supplies use chlorination. Some supplies use bromination.

    All of these variations, as far as is possible, are taken into account with the preparation of B&W and color chemistry on a commercial scale. In fact, part of this is why you have 'European' and 'domestic' chemical supplies from EK. Most photographers are totally oblivious to these facts.

    I can tell you unequivocally that making developers that are prone to forming particulate matter (suspended particles) or working with water that has suspended matter will trap them in the gelatin during process. Even colloidal sulfur formed during decompositon of the fixing bath will lodge in gelatin causing a hazy appearance.

    There is no practical way of removing most of these colloidal particles or 'scum' short of vigorous treatment in sequestrant solutions or organic solvents. This is not advised.

    One of the most prevalent precipitants are ferric and ferrous hydroxide from bleaches and bleach fixes (blixes). These are almost impossible to remove as well, but most people don't know they are present as they are so slight (usually) or have the same color as a color negative d-min.

    As I said before, I am concerned about final quality. Lacking a proper densitometer and sensitometer, and lacking micro measuring equipment, I am unable to test developers other than using gross methods such as the eyeball. I am very concerned that I know that developers can perform on a macro scale quite well, but on a micro scale (1, 10, or 100 micron lines for example) can perform poorly. In fact, suspended micro particles can interfere with MTF and RMSG when trapped in gelatin.

    Therefore, while I appreciate what you and others are trying to do, I am unconvinced of the overall repeatability of many scratch mixed developers for all photographic parameters. Just see the comments on this site, for examples.

    I am not going to trust my results to qualitative measures of chemicals from dubious sources whether they be color or B&W. I am bringing my concerns to the attention of others, and it seems that there is some degree of support for my position which is merely one of caution and reservation, not one of condemnation.

    Thanks for your answer.

    Ron Mowrey
  44. OK, forget swimming pool carbonate. I just received a 17 pound pail of anhydrous sodium carbonate that according to the MSDS that came with it is 100% sodium carbonate. It cost $15.98 + shipping. Is it alright with you guys if I use it?
    I have never seen the symptoms that you attribute to colloidally suspended matter in the interstices of gelatin. The only milky or hazy appearance I have seen went away when I returned the film to the fixer. I guess I have been lucky. But then, most colloidal suspensions I have seen were not water clear. The suspended matter I have seen was not colloidal and precipitated after a time. I have used city water that smelled strongly of chlorine without problem on black and white, except perhaps the removal of the emulsion if I left it in water too long. My well water is not well suited to the use of carbonate of any degree of purity, so I use a borax-NaOH buffer in its place which does not form the precipitate of calcium and magnesium carbonate..

    I'm not telling anyone what to do. I tell a lot of people what I do and the results I get.

    100 grams of non-iodized salt per liter of D-23 made some difference, but did not improve resolution. Rodinal with salt had somewhat mushier grain, but no better resolution. Rodinal 1+50 with 4 g/l of sodium ascorbate did have finer grain and better resolution.
  45. Patrick;

    What was your measure for granularity? Did you measure any other factors such as sharpness? Just curious.

    Also, it is virtually impossible to make any chemical 100% pure. No chemical produced on earth by any man made process is 100% pure. I guarantee that.

    We can come close, but the closer we come the price goes up. Way up!

    Ron Mowrey
  46. You could see for yourself if you can find the back issue. I can't find my own copy since my grand daughter -in-law started organizing my mess.

    The comparison of grain and resolution was done by side-by-side comparison of 40 0r 50 power (Ican't remember which) enlargements. The grain was clearly visible. The difference in resolution was also clearly visible. The Rodinal with ascorbate had much of the appearance of plain Rodinal in that the grain was well defined but smaller. Widths of fine lines were different which I attributed to some degree of infectious development in the plain Rodinal.

    In engineering there is a difference between a specification of 100 and 100.0 and 100.00, the 0's after the decimal signifying the accuracy of the number. The MSDS sheet specified 100%. I don't see anything to get excited about. As you say, nothing is 100.00% pure, but then neither is the expensive stuff. With that specification of 100%, we should be able to presume a purity that will round off to 100%, or in other words, 99.5 % or better. Only if that is not true can we accuse the manufacturers of lying.
  47. Patrick - that's part of the issue here. An MSDS is not a certification of purity - it is a safety guideline that the Dept. of Transportation, industrial hygenists, firefighters and other use to determine the safety associated with a substance. That 100% figure you see most probably means that the sodium carbonate does not have any other added ingredients and that for all practical (read - safety) purposes, is behaves as 100% sodium carbonate. Firefighters do not care if there are minor amounts of something in the sodium carbonate unless it would cause it to behave differently, such as when they spray water all over it. But a MSDS is not an assay of purity.

    You mention accuracy, but what about the error associated with those numbers? If an MSDS says 100%, is that 100 +/- 0.1%, or 0.5%, or 1.7%? We can't tell. That's where having an analyzed reagent or at the least tested to meet the criteria set out in the product specifications is better. Error limits are given to truly know what the error limits are - you can not really be certain that the error is equal to the rounding step, as you assumed above. It most likely is not.

    I've also seen assays on analyzed reagents come up above 100% - that just kind of reflects the nature of the chemical and the method used to determine the assay. It may not really mean the assay is wrong or bad, but it may be just as accurate as an assay that comes up a little under 100%. It's just the nature of the methods used...

    And it's not that the supplier is "lying" about anything. They are just following the guidelines set out by their industry, and those guidelines may not match the guidlelines that the photographic industry follows. That's what Ron is concerned with.


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