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Scratch mixing developers: a problem?


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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

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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.

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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.
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>> 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.

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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.)

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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

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"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?

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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.
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>> [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? http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=006LnU

And is this the link? http://www.genchemcorp.com/products/sodiumsulfitea.shtml

 

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.

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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.

 

Regards.

 

Ron Mowrey

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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.

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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.

 

Dean

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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.
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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.

 

-Mike

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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

permanent.

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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 www.chemistrystore.com 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.

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>> 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, http://www.genchemcorp.com/products/sodiumsulfitea.shtml, 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.

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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.

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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.

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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

 

Introduction:

 

(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.

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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

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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.

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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.

 

Regards.

 

Ron Mowrey

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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

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