Is food grade chemistry OK for use for photography?

Kirk Keyes · Apr 22, 2009

gainer said:
I say if you are willing to pay the premium price and wait for shipment of a chemical that may or may not be better than what you could buy at the grocery, hardware or drugstore, by all means do it.

It looks like you're spreading some Fear, Uncertainty, and Doubt.

I seem to remember in one of the threads I linked to above that 20 Mule Team Borax (your favorite brand of borax) did not meet the specifications for Photo Grade Borax.

So you're making a false claim by saying that it may not be any better when it's demonstratable that it is not an equivalent chemical.

Kirk Keyes · Apr 22, 2009

gainer said:
Morton's canning salt has no additives.

Going back a day...

When Morton say that, they mean that they have added nothing to the salt they may have simply just dug out of the ground. Does that mean it's suitable for photographic use? If you read up a bit about how evaporite minerals are mined and purified, I hope you would realize that it probably means it is not.

If you look around Morton's web site - going past the food grades (which they sell about 11 different food grades) to the industrial grades, they state that they sell over 50 grades of sodium chloride. Are all those grades going to be suitable for photographic use, maybe, but you can't be certain without comparing specifications.

Another thing to remember, as you get into higher grades of chemicals, they become purer. So even though a particular grade of salt says "no additives", that doesn't mean it's pure NaCl, it means they didn't add anything to it from when it came out of the basic mining step. Higher grades have some impurities (and sometimes photographically relavent ones) removed, and that's why they cost more.

You can risk your film, but I prefer to play it safe. I guess it's like buying insurance. No body needs it until it's too late to get it.

gainer · Apr 22, 2009

OK, just how do you play it safe? How do you know what is in the nominal chemical you buy? I did a lot of searching, and only learned that ANSI provides specs for some photo chemicals, and testing procedures, but not sources that meet those specs. You depend on someone's honesty when they say they are selling photo grade chemicals. Furthermore, the iANSI nformation sheet for sodium Tetraborate, Pentahydrate and Decahydrate, begins :

"This is one of a series of standards that establish criteria of purity for chemicals used in processing photographic materials.
Although the ultimate criteria for suitability of a photographic grade chemical is its successful use in an appropriate photographic use test, the shorter, more economical tests described here are generally adequate." (Unerlining is mine.)

It seems that in order to be sure that you are getting the appropriate qualities in what you buy, you must either do the tests described in the ANSI paper, which may not satisfy your requirements because they do not insure analytical reagent purity, or do the practical photographic test, which I have done to my own satisfaction.

With regard to borax, there are only two kinds of impurities: soluble and insoluble. If you make a saturated solution of borax by adding, say, 100 grams of borax to a liter of water, there will be lots of sediment and about 5 grams of borax in solution along with about 95% of the original soluble impurities. Decant that solution and use it for cleaning. Now you have concentrated the insoluble impurities. add another liter of water and you have a saturated solution of borax with less the 5% of the original soluble impurities and none of the insoluble ones. You can make several more liters of this degree of purity from the sediment.

gainer · Apr 22, 2009

Kirk Keyes said:
Well, that's why you buy from quality manufacturers. (I can't recommend the people that made the Chinese Amidol a few years ago...)

And come on, I know you realize how silly your comment is here. If a bucket is not good enough, you're implying that the entire quantity of anything must be tested inorder to guarantee the quality of the entire lot. Now that's silly!

I think your ststement here shows that I have more experience with random sampling than you do. Every test has the possibility of random error of measurement, as well as consistent error. The analysis of samples by the method of minimum variance, provide an estimate of variance of each variable, and a measure of confidence in the mean. The fewer the measurements, the less the confidence. When a chemical is a powder, the distribution of impurities is likely to be non-uniform. No, I don't realize nor do I accept your judgement that my comment was silly.

Kirk Keyes · Apr 22, 2009

gainer said:
OK, just how do you play it safe?

I buy Photographic Grade as it's the cheapest grade can be trusted to meet the needs of photography. As I don't run curves with every batch (OK, almost...) and I don't check the resolution of my film/developer, I use what the industry has specified as "safe".

For less common stuff, ACS grade (American Chemical Society), and AR (Analyzed Reagent) grade are your next best choice. I have a ACS chemical specification book and I can look up stuff to see if there's interferences, and they list the associated test for each item in the spec for more reading enjoyment.

AR Grade, is most certainly overkill, as it's typically ACS grade where each lot sold by the manufactuer has the actual analysis results from the ACS analysis printed out so you can see what the result is.

alanrockwood · Apr 22, 2009

If I may offer an unsubstantiated opinion, the biggest source of impurities and contamination in photo solutions, regardless of the grade chemicals used is likely to be from the tap water used to make the solutions.

This of course does not apply to those who use purified water for making photographic solutions.

Kirk Keyes · Apr 22, 2009

That's a good point, Alan. I understand that Pat has relatively poor water available where he lives (high mineral content) where as I have really good water available here from the tap. But for critical applications, like emulsion making, I do use deionized water.

Kirk Keyes · Apr 22, 2009

gainer said:
It seems that in order to be sure that you are getting the appropriate qualities in what you buy, you must either do the tests described in the ANSI paper, which may not satisfy your requirements because they do not insure analytical reagent purity, or do the practical photographic test, which I have done to my own satisfaction.

And that's why I buy photograde as the work to ensure that it meets ANSI spec. has been done for me.

Photo Engineer · Apr 22, 2009

alanrockwood said:
If I may offer an unsubstantiated opinion, the biggest source of impurities and contamination in photo solutions, regardless of the grade chemicals used is likely to be from the tap water used to make the solutions.

This of course does not apply to those who use purified water for making photographic solutions.

I agree for emulsion making, but for normal processing this is not much of a problem in most areas.

One of the biggest problems in "bad" chemicals from whatever source is the fine particles that may be present and which may form a suspension in processing solutions. Both Patrick and I have mentioned this above. These suspended particles cannot be filtered out and can do great harm to a negative. The harm increases as negative size decreases as the apparent size of the particles increases.

I experienced a quite noticable improvement in my film work when I installed a very good water filter system in my darkroom. Filterable particles in the city water supply were a problem from time to time and could leave scratches and marks on my film and even on prints.

PE

Kirk Keyes · Apr 22, 2009

gainer said:
When a chemical is a powder, the distribution of impurities is likely to be non-uniform.

I think you seem to think that products are not mixed so that they have a generally uniform consistency...

Kirk Keyes · Apr 22, 2009

gainer said:
With regard to borax, there are only two kinds of impurities: soluble and insoluble. If you make a saturated solution of borax by adding, say, 100 grams of borax to a liter of water, there will be lots of sediment and about 5 grams of borax in solution along with about 95% of the original soluble impurities. Decant that solution and use it for cleaning. Now you have concentrated the insoluble impurities. add another liter of water and you have a saturated solution of borax with less the 5% of the original soluble impurities and none of the insoluble ones. You can make several more liters of this degree of purity from the sediment.

That sound's like a lot of work and fuss when I can simply grab my bottle of borax and and weight out 2 grams for D-76.

It's really about product specifications - do you want to use products that are designed to meet the needs of a particular use, or do you want to be fiddling around, second guessing, and spending a lot of time doing things to chemicals when you can just grab it off the shelf and be assured it's going to meet your needs.

And when something goes wrong - was it because you didn't let your borax solution settle long enough, or you didn't quite good your baking soda long enough, or your swimming pool pH plus had too much sediment in it, along with all the other things to go wrong in the darkroom, what does the average person do to figure out where things went wrong? I just hope they were not truly important photos.

Photo Engineer · Apr 22, 2009

Kirk Keyes said:
I think you seem to think that products are not mixed so that they have a generally uniform consistency...

Kirk;

I believe that you will find that as impurities increase, uniform consistency goes down. This is why you see separation in some powdered developers and fixes. The mix of chemicals can be considered a mix of impurities of different hydration, crystal habit, size and shape and this affects uniformity.

PE

gainer · Apr 22, 2009

Let me just point out a couple of things and then I'll quit.

I have been using 20 Mule Team Borax for as many years as I can remember with no sign of any defect in processing that was not the effect of a miscalculation on my part. The preparation of a saturated borax solution in large quantity that has no more than 5% of the original soluble impurities and none of the insoluble ones takes little time. If it has sediment to begin, its concentration will be a known function of temperature. It is easier to measure out 426 ml of this solution to make the basis of your liter of D-76 than it is to weigh out 2 grams of a less pure version. 420 to 430 is a smaller percentage than 2.1 to 2.2. Kodak's recommendation for accuracy of home brewed solutions was +or- 0.1 grams. The liquid concentrate is better for accuracy as well as for convenience and purity, especially when small quantities are to be used.

wogster · Apr 22, 2009

gainer said:
Let me just point out a couple of things and then I'll quit.

I have been using 20 Mule Team Borax for as many years as I can remember with no sign of any defect in processing that was not the effect of a miscalculation on my part. The preparation of a saturated borax solution in large quantity that has no more than 5% of the original soluble impurities and none of the insoluble ones takes little time. If it has sediment to begin, its concentration will be a known function of temperature. It is easier to measure out 426 ml of this solution to make the basis of your liter of D-76 than it is to weigh out 2 grams of a less pure version. 420 to 430 is a smaller percentage than 2.1 to 2.2. Kodak's recommendation for accuracy of home brewed solutions was +or- 0.1 grams. The liquid concentrate is better for accuracy as well as for convenience and purity, especially when small quantities are to be used.

When dealing with insoluble impurities, how much of this stuff will settle out if you mix it with water and leave the bottle on the shelf for a couple of days? Even in very small particles, so you can simply decant off most of the chemical and toss the last 100ml or so with the impurities.

Photo Engineer · Apr 22, 2009

Paul;

Sometimes a fine colloidal suspension which cannot be filtered out will remain in suspension forever! That is one of the key problems to this methodology. You just cannot be rid of it.

PE

Kirk Keyes · Apr 23, 2009

gainer said:
It is easier to measure out 426 ml of this solution to make the basis of your liter of D-76 than it is to weigh out 2 grams of a less pure version. 420 to 430 is a smaller percentage than 2.1 to 2.2. Kodak's recommendation for accuracy of home brewed solutions was +or- 0.1 grams. The liquid concentrate is better for accuracy as well as for convenience and purity, especially when small quantities are to be used.

You've left out some very important information here. Vital to anyone that is going to try this approach.

Before I get to that, I'd like to say that I have an inexpensive (<$20) digital scale that I bought new. It reads to 100g, with a resolution of 0.01g. Before you say it may be off by more than a gram as you mention above, I 've checked the linearity of its calibration with certified weights and it's right on, within 0.01 g at every weight I checked.

The solubility of most anything, including borax, is highly dependant on temperature. You've left out that very important bit of information. Looking at the following info: http://www.borax.com/pdfs/dist/Profile_Borax_Decahydrate.pdf
states that a saturated solution of borax decahydrate at 15C is 3.79% by wt, at 20C it is 4.71%, and at 25C it's 5.80%.

Now this does not match what you appearantly say the solubilty of a saturated solution of borax is in an earlier post - you state:

If you make a saturated solution of borax by adding, say, 100 grams of borax to a liter of water, there will be lots of sediment and about 5 grams of borax in solution along with about 95% of the original soluble impurities.

I take that statement to mean that 1 liter of water dissolve 5 grams of borax decahydrate when saturated. That's quite a bit off what the borax.com info says. You go on to say in my first quote here, that 426 ml of saturated borax will ge equal to 2.0 grams of borax. That equals a concentration of about 4.7 g/L. (So is it 5 g/L or 4.7 g/L? That a difference of about 5%.) But that bit really doesn't matter, as you are further off than 5%.

The borax.com table says at 20C, the solubilty of borax is 4.71% by wt (they don't say if that's %wt/wt or %wt/vol, but I'll assume %wt/vol since that's what most people seem to use.) 4.71% wt of 1L is 47.1g/L. 100 ml would have 4.71 g at 4.71%. Your value is off my nearly a factor of 10. That's a pretty big error. Maybe you meant that you would use about 42 ml of a saturated solution at 20C to get 2.0 grams of borax. I most certainly would have screwed up my D-76 if I'd followed your instructions.

More importantly, the solubility of saturated solutions is dependant on temperature. My darkroom can be 15C in the winter and above 25C in the summer. If I used this technique in my darkroom, I'd have to have a table of solubilities or a graph so that I could calculate the proper amount as the seasons change. That seems like a big pain in the butt, to me.

I still think that it's much easier to get my scale and weigh out 2.00 grams of borax. And it's a lot more accurate than following your instructions, especially when they have an error that off by a factor of 10...

wogster · Apr 23, 2009

Photo Engineer said:
Paul;

Sometimes a fine colloidal suspension which cannot be filtered out will remain in suspension forever! That is one of the key problems to this methodology. You just cannot be rid of it.

PE

Okay so the answer is not all of it, which I why I asked if that would work.

gainer · Apr 23, 2009

Yes, I made a huge boo boo. Somewhere in APUG I described the process with the right numbers. I am in fact happy that I only need 42.55 ml of the solution that was saturated at 20 C. I did say "about" 5, not exactly 5, and that was for the purpose of estimating the reduction of soluble impurities. I should have estimated that the first iteration would reduce the soluble impurities by about half, but that would have been wrong as well. The real reduction depends on the ratio of the volume of saturated solution in the clear liquor that can be decanted to the part the remains with the remaining borax. If we can decant or filter 80 percent of the water that we put in, we will have removed roughly 80% of soluble impurities along with about 47 percent of the 100 grams of borax, which is to be discarded or used for laundry or diaper pails. Oh, I forgot. We don't use diaper pails anymore. Too bad. We still have enough sediment to make a liter of borax stock solution that is definitely pure enough for D-76, and we have not had to weigh anything to the nearest gram, let alone milligram. And if we know the temperature of the final saturated solution, we know its concentration. If we decant that solution and keep it at a slightly higher temperature we can use it 43 ml per liter to make D-76.

I have not seen any sign of colloidal suspension in my borax solutions. If it is there and cannot be filtered out, it will probably be there in any grade of borax. Is a borax solution a favorable environment for a colloidal suspension?

Photo Engineer · Apr 23, 2009

Calcium salts tend to form colloidal suspensions in an alkaline environment. They can be as cloudy as milk or so fine that they are nearly invisible. They are removed during preparation of pure products by a method called flocculation similar to the method used to clear up a cloudy swimming pool.

The flocculating agent is then removed.

So yes, borax and carbonates are both favorable environments for colloidal suspensions, and no, they are not present in all grades as they can be removed.

And, the concentration of saturated solutions varies by as much as Kirk says, therefore leading to the possibility of extreme errors in alkali concentration between a hot and a cold day therefore changing the pH of the developer and its activity.

PE

richard ide · Apr 23, 2009

MY BRAIN HURTS

Photo Engineer · Apr 23, 2009

The ulitimate in what amounts to a colloidal suspensions of Calcium salts in water!

http://en.wikipedia.org/wiki/Whitewash

And, a very clear explanation of what can take place in a film if one has any Calcium salt left in it. A good acid stop and fix can sometimes help alleviate this problem, a fact that I had forgotten to mention earlier, but since so many use a rinse after development instead of a stop and use a neutral or alkaline fix, it was not foremost in my mind when I made the earlier posts.

PE

gainer · Apr 24, 2009

Incidentally, my factor of 10 boo boo is not as bad as one would think. Vestal and Schwalberg, some years ago, experimented with just that, using 20 or more grams of borax per liter of D-76, in an effort to get max speed. I don't remember what came of it, so I am about to repeat it myself. I ran out of hydroquinone, so am using catechol. This brings up the fact that for many photographic uses (I do not speak about such things as emulsion making) the exact concentration is probably not critical. (Two weasel words and a disclaimer in one sentence--reminds me of old NACA days.) Anyway, I'm sure that proper experiments will show that the activity of D-76 will not be appreciably changed by doubling the amount of borax, though its capacity may be.

My calcium supply for bodily health is my well. The water is clear and tastes very good, but clouds up when I use a carbonate in my developer. Consequently, I use a lot of metaborate or borax-hydroxide combinations in developers.

Kirk Keyes · Apr 27, 2009

gainer said:
Incidentally, my factor of 10 boo boo is not as bad as one would think.

I once had a physics professor who told the class that if one was able to measure basic, universal constants to within a factor of 10, then we were doing quite well.

Of course, he was talking specifically about measuring the gravitational constant, G, and the technique at hand was that used by Cavendish in 1798 where he used a horizontal torsion balance constructed from two heavy, lead weights mounted on a long beam. Additional lead weights were placed near the ends of the beam and the oscillation rate of the beam was measured.

Cavendish came quite close to what modern techniques for G measure. In the class, we used bowling balls, and a laser to measure the displacement of the torsion balance. With only about 40 minutes of time, we were within about a factor of 10, hence his comment.

However, for our homework, the professor did not give us a factor of 10 error for our resuts there. For that, we had to be much, much closer. A factor of 10 did not cut it at all...

I think I would be dissappointed in my "D-76" if I used 10 times too much borax in it. I suspect it would be a bit grainier, and not the nice, all-round developer that D-76 is known to be.

Philippe-Georges · Apr 27, 2009

gainer said:
Incidentally, my factor of 10 boo boo is not as bad as one would think. Vestal and Schwalberg, some years ago, experimented with just that, using 20 or more grams of borax per liter of D-76, in an effort to get max speed. I don't remember what came of it, so I am about to repeat it myself. I ran out of hydroquinone, so am using catechol. This brings up the fact that for many photographic uses (I do not speak about such things as emulsion making) the exact concentration is probably not critical. (Two weasel words and a disclaimer in one sentence--reminds me of old NACA days.) Anyway, I'm sure that proper experiments will show that the activity of D-76 will not be appreciably changed by doubling the amount of borax, though its capacity may be.

My calcium supply for bodily health is my well. The water is clear and tastes very good, but clouds up when I use a carbonate in my developer. Consequently, I use a lot of metaborate or borax-hydroxide combinations in developers.

What (or who) is boo boo?

Philippe

Kirk Keyes · Apr 27, 2009

leicam5 said:
What (or who) is boo boo?

Philippe

A "boo boo" is a mistake. Usually considered a little one, or used with little childern when referring to small injuries.

Is food grade chemistry OK for use for photography?

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