Citric Acid

Rlibersky · Feb 10, 2006

Is there a purity issue with buying Citric Acid from a local wine making company. They sell it for 3.25 a LB as opposed to Photo Formularies 6.95 a LB.

df cardwell · Feb 10, 2006

Using it for stop bath or in a film developer ?

That's the issue... don't know what's in the stuff from the wine making guys.

Probably be OK

.

avandesande · Feb 10, 2006

Rlibersky · Feb 10, 2006

df cardwell said:
Using it for stop bath or in a film developer ?

That's the issue... don't know what's in the stuff from the wine making guys.

Probably be OK.

Was thinking of using it with MS Amidol Formula.

David A. Goldfarb · Feb 10, 2006

I use it in such a small quantity (3g/l in Smith's amidol formula), that it wouldn't make much of a difference to spend the extra $3. Once or twice a year I'll go whole hog and use 15g to decalcify the espresso machine, since even at $6.95 a pound it's a heck of a lot cheaper than the little 15g packets they sell in the grocery store.

sanking · Feb 10, 2006

If you use it in really large amounts you can get it for as low as $1.40 a lb. here, http://chemistrystore.com/citric_acid.htm

Sandy

David A. Goldfarb said:
I use it in such a small quantity (3g/l in Smith's amidol formula), that it wouldn't make much of a difference to spend the extra $3. Once or twice a year I'll go whole hog and use 15g to decalcify the espresso machine, since even at $6.95 a pound it's a heck of a lot cheaper than the little 15g packets they sell in the grocery store.

gainer · Feb 10, 2006

Rlibersky said:
Is there a purity issue with buying Citric Acid from a local wine making company. They sell it for 3.25 a LB as opposed to Photo Formularies 6.95 a LB.

Makers of wine for sale are bound by regulations we could not abide. Smoking an empty bottle with a sulfur candle to sterilize it requires them to list sodium sulfite on the label. I'll ask some friends who sell wine, but I suspect that they would not use less than the best purity they can get. Even if regulations do not require utmost purity, taste may.

avandesande · Feb 10, 2006

Food grade chemicals go through much of the same handling and purity safeguards as pharmaceuticals.

dancqu · Feb 10, 2006

Rlibersky said:
Was thinking of using it with MS Amidol Formula.

Ball Citric Acid, 6 ounce bottle. Look for
with the canning supplies. It may go by
the name Sour Salt. Perhaps the
Kosher department?

Photographer's Formulary offers most chemicals in
very small to very large amounts. Some of those small
amounts go a very long way. Dan

Photo Engineer · Feb 10, 2006

Many of you don't understand the fact that food grade is often less pure than photograde.

Just as an example, photograde sodium chloride (NaCl) must be virtually 100% free of bromide and iodide salts, but food grade may contain quite a bit of both of those salts.

Photograde chemicals must be free of iron salts, but food grade may contain them at low levels that would ruin a photographic emulsion.

In this case, if the citric acid is reasonably pure, it will work in a stop bath or fixer, but in a developer would require at least a test for results. I would say that purity of stop and fix chemistry is much more lax than developer purity.

I would also add that some impurities when present in developers affect image strutcture more than image quality so that the tone scale might be fine, but the grain or sharpness might suffer.

Of course, I've been trying to explain this for several years, but most people tend to ignore the fact that food grade and photo grade are different. Pool supplies are a whole other painful topic, especially sodium carbonate which may be quite impure for pool use and not very good for your film. Just as an example, if the impurity is very fine sand in sodium carbonate (or in citric acid for that matter) what do you think that sand is going to do during development?

Just some 'food for thought'. Pun intended!

PE

rjs003 · Feb 10, 2006

Citric acid in wine making is used for cleaning of the wine making equipment. We mix citric acid and sulfuric acid with several gallons of water to form a cleaning solution;which is used to clean the hoses, pumps and tanks that are used in the wine making process. Yes these chemicals are food grade.

avandesande · Feb 10, 2006

Yeah if you are manufacturing millions of dollars worth of film stock you need to be sure about these things but in reality they would make little difference in a home-made emulsion. (citing the salt case)

Bet you dollars to donuts the citric acid PF has and you buy in the food store come from the same factory and is of the same purity.

Photo Engineer said:
Just as an example, photograde sodium chloride (NaCl) must be virtually 100% free of bromide and iodide salts, but food grade may contain quite a bit of both of those salts.

Photo Engineer · Feb 10, 2006

avandesande said:
Yeah if you are manufacturing millions of dollars worth of film stock you need to be sure about these things but in reality they would make little difference in a home-made emulsion. (citing the salt case)

Bet you dollars to donuts the citric acid PF has and you buy in the food store come from the same factory and is of the same purity.

A very very tiny impurity of either iodide or bromide in an AgCl emulsion will make a huge change in an emulsion, of up to 1 stop in speed or one contrast grade. I just did that experiment today to test this out!

PE

Maine-iac · Feb 11, 2006

Photo Engineer said:
Many of you don't understand the fact that food grade is often less pure than photograde.

Of course, I've been trying to explain this for several years, but most people tend to ignore the fact that food grade and photo grade are different. Pool supplies are a whole other painful topic, especially sodium carbonate which may be quite impure for pool use and not very good for your film. Just as an example, if the impurity is very fine sand in sodium carbonate (or in citric acid for that matter) what do you think that sand is going to do during development?

Just some 'food for thought'. Pun intended!

PE

Theoretically, you may be correct; in practice, I've been using common over-the-counter products like Arm & Hammer Washing Soda or pH Plus (both carbonate) from a pool store or Vitamin C powder or crystals from the health food store for years, in all my formulas, and I have never had a bad experience that I could trace to the chemicals involved. To my own stupidity, yes, but not to the purity of the chemicals. Even when I've used Vitamin C that has Rose Hips in it, the only thing that happens is that the tiny particles of rose hips do not dissolve and precipitate out on the bottom of the beaker. No effect on the developer at all. I've concluded that Pat Gainer is right when he insists that many photographic processes work well when the standard of "close enough for government work."

Larry

Photo Engineer · Feb 11, 2006

I would like to explain something.

I am in favor of the adage "use what works for you". So, feel free to ignore anything I say on this and any other topic.

OTOH, as a scientist and engineer, I feel it my duty to warn you all of possible pitfalls. In fact, I have been in the situation of "I told you so" too many times, and this has sensitized me to the problem. I get lots of e-mail from people asking for help after the fact, and I answer them all.

So, Larry, have you checked to see if those little particles of rose hips are getting into your film and leaving small dark spots on the negatives, or are they scratching the negatives? Others have observed that. Once a particle gets trapped in the swollen gelatin, it won't come out. Look closely under a jewelers loupe. You may or may not see a problem.

If it works, use it, but if not - please don't say I have not given all of you fair warning of the potential pitfalls.

PE

avandesande · Feb 11, 2006

Chemicals are only as good as their assay. I used to work for a tiny place, we made pharmaceutical precursers and sent the stuff to italy for 'fda processing' and was sent back to the states. We made food flavorings that went by the same treatment. We also sold chemicals that went into the Aldrich catalog. I have cut up 12kg ingots of sodium and had sweat roll off my nose and sizzle on the surface.

There is no guarantee that if you buy stuff from a manufacturer that it will meet your needs, food grade or otherwise. You just have to understand the impurities the best you can and then do test runs to determine if the materials will work for you.

sanking · Feb 11, 2006

Ron,

Just curious, do you filter your emulsions? If so, with what kind of filter?

Sandy

Photo Engineer said:
them all.

So, Larry, have you checked to see if those little particles of rose hips are getting into your film and leaving small dark spots on the negatives, or are they scratching the negatives? Others have observed that. Once a particle gets trapped in the swollen gelatin, it won't come out. Look closely under a jewelers loupe. You may or may not see a problem.
.

PE

gainer · Feb 12, 2006

I wouldn't say that ignoring what PE has to say is the right thing to do. A better term is "take it under advisement". Check it out in your own circumstances. Working in a test and design lab is perhaps more critical than commercial photography. Certainly you must be as sure as possible that anything you discover or design wasn't just some accidental impurity that might not be in the next batch. It's not always possible to get the reagent grade, and so a knowledge of what impurities are most likely to be present and what finding out what effect they can have on the product is, I would think, an important part of testing. For example, I know my well water is very hard, and I know some developer formulas need either demineralized water or a chelating agent.
I'm rambling, but I just want PE to know that I take what he says under advisement. If I don't think the advise is necessary, I test it without rejecting it out of hand. Who knows, I might be wrong some day.

Jordan · Feb 12, 2006

When I was a grad student, members of another research group evaluated the purity of some of the anhydrous reagents provided by Sigma-Aldrich (a highly trusted chemical supplier to the academic research community). They found significant water content in some materials, straight from the Aldrich warehouse, and lower-than-stated reagent concentrations (due to water-induced decomposition) even in hermetically sealed bottles.

I guess the moral of the story is that you need to test your materials carefully before committing them to anything critical. You can often get away with lower than photo-grade materials, but sometimes even research grades may not be pure enough.

Photo Engineer · Feb 12, 2006

To all;

As I said before, use what works for you.

Sandy;

I don't filter my emulsions due to time constraints, but I would for critical work. I would use a stainless steel filter for the purpose. I do use a paint filter at times though for washing emulsions to hold back the emulsion and let wash water through. The stainless steel grade is important. You cannot use any grade of SS that is magnetic, as the level of impurities is too high for the emulsion.

I do pick up some small particles in my coatings due to lack of filtration, and when I go to serious film coating, I will be filtering the emulsion. But, you would be surprised at how uniform the coatings are. You see, the gelatin emulsion coats the dust and the dust therefore becomes part of the image. I don't recommend that for critical work though such as a film coating.

Another good practice is to degas your emulsion using an aspirator and 'jolt' it with low pressure to allow bubbles to form and come to the surface. Filtration after the vacuum jolt will help in this bubble removal. I have an aspirator for this purpose and will try to bring it with me this June for you to see.

PE

Gerald Koch · Feb 13, 2006

I once found a dead moth in an unopened 1# bottle of reagent silver nitrate. So much for quality control.

People tend to think of photograde chemicals as being of high purity. But, the only restriction on photo grade chemicals is that they do not contain anything which would cause adverse effects to photographic emulsions. There is no requirement that they be particularly pure, in fact they may be less pure than food grade or other grades. For example, 1% sodium sulfate in a particular lot sodium sulfite would probably be allowed but even the very smallest amount of sodium sulfide would not.

Photo Engineer · Feb 13, 2006

Gerald Koch said:
I once found a dead moth in an unopened 1# bottle of reagent silver nitrate. So much for quality control.

People tend to think of photograde chemicals as being of high purity. But, the only restriction on photo grade chemicals is that they do not contain anything which would cause adverse effects to photographic emulsions. There is no requirement that they be particularly pure, in fact they may be less pure than food grade or other grades. For example, 1% sodium sulfate in a particular lot sodium sulfite would probably be allowed but even the very smallest amount of sodium sulfide would not.

Gerald, you just made my point.

That same 1% impurity of halide salts in pool grade sodiium carbonate could ruin a developer.

That same 1% impurity of iodide in chloride could ruin an emulsion.

And the list goes on. Generally you do want a reagent grade of chemicals for photography, that being about 'photograde'.

I will say again however; use what works for you.

PE

dancqu · Feb 13, 2006

Rlibersky said:
Is there a purity issue with buying Citric Acid from
a local wine making company. They sell it for 3.25 a
LB as opposed to Photo Formularies 6.95 a LB.

There may or may not be an issue. There is no issue
when purchasing Photo Grade. As PE has pointed out
Photo Grade is not just an advertising gimmick. Check
that out for yourself by searching the WWW for a few
chemicals used in the darkroom. Then compare impurity
tolerance levels against food and another grade or two.

For myself I will continue to support this industry. This
is no time to be tight fisted. Let those in the home-brew
wine and beer business and those in the swimming pool
business sink or swim on their own. Dan

Citric Acid

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