How pure is pure enough?

[silent1]

I was looking at the local supermarket for distilled water to use in

mixing photo chemicals. I'm not sure it's necessary; all the film I

developed in high school was done in chemistry mixed with tap water,

but tap water varies a great deal from place to place, and I live in a

city now (with lots of chlorine in the water).

 

Unfortunately, I didn't find any actual "distilled" water; I did find

a couple brands of "purified" water that was marked as "deionized or

reverse osmosis filtered." That got me thinking -- the drinking water

I buy in bulk, refilling my own 2- or 3-gallon jug, is reverse osmosis

filtered, as well as carbon and micron filtered, same as the

"purified" water that was marked for 99 cents per gallon. Would this

kind of filtered drinking water be pure enough (at 39 cents per

gallon) to get reliable results in photo chemistry? Are there other

known problem factors in water supply other than pH and dissolved

calcium (for instance, water system chlorine, dissolved iron oxides

from rusty pipes, etc.)? Should I just use tap water and not worry

about it (the water here is soft enough, just overly chlorinated)?

[db1]

I just picked up distilled water today for 58 cents a gallon at Wal-Mart. Got a Wal-Mart in your town? I'm sure you do.

[johnmarkpainter]

It will vary depending on your local water supply.

 

Steam Distillation is more complete....Reverse Osmosis water quality will vary

depending on the quality and maintenance of the Filter system.

 

I would try to get information on the content of your water supply and go from there.

 

Chlorine is easy to filter out with cheap filters.

 

jmp

[lex_jenkins]

Even tho' I talk a lot here about using distilled water and filtering my tap water I'm not really *that* picky about it.

 

As long as I don't actually see any particles floating around or settled at the bottom of my filtered water I consider it good enough for most uses. I'd apply the same standard to bottled water - if you don't see any residue at the bottom it's probably good enough.

 

I use distilled water for making stock solutions of all my chemistry as well as for working solutions of film developers.

 

I use filtered tap water (which runs through a water softener on our well pump) for stop bath and film wash water. A single Brita pitcher makes enough filtered water for two rolls of 120 film.

 

I use ordinary tap water for washing prints. I'm planning to install either a faucet or inline filter for all my photoprocessing needs, tho', mostly because of occasional problems with actual chunks of lime deposits breaking off from the insides of our plumbing and becoming embedded in print emulsions - RC prints seem more vulnerable to this than fiber prints, for some reason.

 

I wouldn't worry much about chlorine from city tap water or bottled water - let it sit for 24 hours and the stuff will dissapate.

[chris_eve]

If chlorine is your only problem, just let the water stand for a few hours before use in a plastic container ... most of it will gas off. There's a noticeably greater amount of chroline in our local water in the summer, you can smell it as you run the tap, but I've never noticed any problem with colour or b&w chemicals. However, if I draw hot water from the tank rather than cold direct from the main I've had colour shifts with C41 film, so I don't do that any more.

[winfried_buechsenschuetz1]

When I was not yet using one-shot developpers I used tap water only for developper dilution. But before using it, I boiled it for 10 minutes and let it rest over night. It's amazing what kind of stuff falls out after boiling and resting. I only used the top half of the (unstirred) can of water I prepared and never had any problems with the developers.

 

For all other agents such as fixing baths etc plain tap water will be sufficient.

[pascal_miele]

If you can drink it.....you can use it for dev !

 

The chemicals for photo use are not 99.9999999 pure, it's only industrial grade.

 

Pure water is a unnecessary luxe (except for some special process like some alt process)

[doremus_scudder1]

Donald,

 

Purified water is certainly alright for mixing photochemicals. Most tap water is as well. The main concerns with tap water are:

 

Hardness, (calcium carbonate) which can change pH of developers and therefore activity. If your water quality is consistant, this is not a huge problem, just calibrate (I have harder water in my European residence than in my darkroom in Oregon and have two different developing times for PMK).

 

Dissolved minerals, mostly metals, that can alter chemical activity and wreak havoc with toners, fixer life, etc. City tap waters usually do not have much of this type of contamination. Well water is the chief culprit. If you have a well and lots of dissolved minerals, you should think about a reverse-osmosis or other filter system for your drinking water anyway. Drinking water filtered in these ways is fine for photo purposes.

 

Suspended solids that get stuck on film/paper emulsions. These filter out as well.

 

One note of interest, softened water that has been softened using ion replacement has a lot of salt(s) in it. If you use this for your final wash, you can get salt crystals resulting from evaporation deposited on your negatives. The same holds true for hard water: It can leave mineral deposits as well. Therefore, the distilled/purified water is a good idea for a final wash and probably more important there than for mixing developer if you have reasonably drinkable tap water. I wash in tap water (my film, I mean) and give my film a final 2-5 minute bath in distilled water mixed with a wetting agent. This I use one-shot to avoid mineral build-up which would then get re-deposited on the film. I've had no problems with water spots on paper as long as I squeegee well.

 

Cheap inline filters are available that filter down to 5 microns. I have one on the line to my film washer. Brita and Pur systems on taps are excellent as long as you replace the filters regularly.

 

In your case, I would just use tap water for everything except the final rinse. Chlorine is not that big of a factor in photo processing. On the other hand, if you have a charcoal filter system already, just use water from it for photo purposes. It will eliminate the chlorine.

 

So, bottom line, use the cheapest purified water you can find for final wash and maybe developer mixing (or see if your tap water will give acceptable results for the developer) and stop worrying about contamination problems.

[tim_curry]

In the southwestern U.S. we have very hard water (Tucson is reputed to be the kidney stone capitol of the U.S.). At a local "water store" here distilled water is going for $0.30 per gallon if you bring your own container. I use distilled for mixing chemistry and final rinse. For stop bath, washing, etc. I just use tap water, especially since the tap water is now finally below 94f.

 

The biggest problem you could have from tap water is a variation in development times when using OTHER PEOPLE'S TIMES from tables you find. Once you have done film tests with your own darkroom, the main concern is just to use the same chemistry, thermometer, stop, fix, etc. Consistency of technique is more of a concern at that point than water.

[conrad_hoffman]

I use filtered tap water for everything. If it tastes ok and doesn't have junk floating around in it, it's probably fine for photo. If you're really concerned, boil it. That will take care of the chlorine and much else will settle out. Distilled is overkill unless you get it really cheap or you're doing calibrated lab work.

[jorge_oliveira2]

I have a problem with my tap water. Tiny little spots in the neg...

 

Filtering the water took care of it.

[tim obrien]

Ya sit down and develop one roll (or sheet) of film in distilled water and one in tap water, filtered or not. If you can tell the difference, you have your answer, if you can't, you have your answer.

 

Me, I have seen the difference, and all my films get developed in steam distilled water, get stopped in tap water, get fixed in hypo made with distilled water, washed in tap water and final washed in distilled water with LPN. I am pretty happy with the results. It takes about a liter of water to do the day to day processing for one roll of 120 or two rolls of 35mm, two liters of water for 5 sheets of 2 1/4 x 3 /4 or 3 1/4 x 4 1/4 or two sheets of 4x5. at 20 cents a liter, what the hey?

 

Keep up the good work Donald.

 

tim in san jose

[Andrew in Austin]

25 cent a gallon filtered water from the neighborhood grocery store's vending machine seems good enough. It makes a good cup of Joe, too.

[patrick_gainer]

Hard water is better than soft for drinking. Incidence of heart disease is lower where the water is hard.

 

I don't like my hard well water for developers with carbonate as it forms a cloud which eventually precipitates, taking part of the carbonate with it. Developers using borates are fine with it. I use rain water, water from my dehumidifier or store bought distilled water to avoid the calcium and magnesium.

[mike_scarpitti]

Most mfrs of developers assume they're gouing to be mixed with tap water and adjust the formulaes accordingly.