Is food grade chemistry OK for use for photography?

Hi,

I just got back from a wine making outfit and I noticed it had some chemicals that I use for my film and paper developers, like Citric acid, sodium metabisulfite and ascorbic acid. The prices were WAY lower than what I paid from my chemical supply house (which also comes with a steep shipping fee as well). Would the chemicals be OK to use for photo purposes and has anyone tried this before? I suppose I could buy some to try out, but I thought I would ask the esteemed experts here first. Thanks in advance.

They are probably fine.

As Jordan says, you will most probably be fine. The thing to keep in mind (and this is not said to put you off using the food grade materials), is that the photo-grade, and the food-grade chemicals will most probably be tested for purity on the basis of different contaminants.

For instance. The level of insoluble material in a material bound for a film developer is likely to be carefully monitored in QC, as insoluble bits on the film could make for a lot of spotting; whereas in something like sodium metabisulphite used for sterilising wine making equipment, higher levels of insoluble material are unlikely to be a problem.

Having said that! The food- and photo-grade materials you mention may actually come from the same feedstock, and just have to pass the appropriate quality tests.

The way I understand it, food grade chemicals are less pure than technical grade, which is usually good enough for home brew photo chemistry. That doesn't mean the stuff is not good. It may be perfectly fine. I would expect a simple stop bath made of citric acid and water to work perfectly. Developers made with food grade ascorbic acid, might need a little testing, since the sodium isoascorbate derived from the ascorbic acid is an active reducing agent . Come to think of it, you'd probably save a whole lot on food grade sodium sulfite as well.

For photo use, there is no difference between ascorbic acid and its mirror image, isoascorbic acid. I have used both. The body knows the difference, as the isomer is not Vitamin C.

The answer depends upon how critical you wish to be. If you are a purist and care about your film and prints to the Nth degree, then photo grade is the way to go.

If you are a hobbyist and do 4 rolls of film/year of the kiddies in the backyard with the dog, then you may wish to drop a notch and go with food grade.

Me? I tend to blend the two. I use Rodinal (pre-made), P'Cat HD with photo grade chems, and D-76, et al, with a blend of photo grade chems and the dreaded 20 Mule Team Borax, GASP!

I have not seen a problem with food grade chems, but that does not mean a problem couldn't exist. Use what works for you.

What is the definitio of Photo grade and how does it differ from Technical and Laboratory grades? What is Food grade? Why should Food grade not be at least as pure as Technical? Ascorbic acid is available in a technical grade, not intended to be used as Vitamin C. I have used it. I found that I can get 3 pounds of Vitamin C ascorbic acid from NOW Foods for the price of 2 pounds, not to be used as vitamin C, from the Chemistry Store.

Before I can logically reject a chemical that is only, say, 98% pure, I must know if the impurities are harmful in any way to my photographic processes. I cannot measure the small quantities required of some of them as closely as 2%. Don't quote the precision of some digital scales. They can measure to the microgram and still be off by a gram, and can be nonlinear to boot. Precision and accuracy are not the same, as one may learn in surveying and map making.

Enough ranting.

gainer said:

What is the definitio of Photo grade and how does it differ from Technical and Laboratory grades? What is Food grade? Why should Food grade not be at least as pure as Technical?

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Pat, we've covered all this before...

In fact, it is so well covered that it is easier to rehash than to uncover.

Kirk, it would have been more helpful of you to remind an 82-year old where to find the previous coverage, which would also inform th OP and those who folloewd where to find it, than to admonish me for "digging up dead horses".

I think that the answer here can be yes and no both depending on the chemical.

Food grade salts such as Sodium Chloride or Sea Salt are not usable in developers or fixers. Borax may contain harmful insoluable matter, and so may some carbonate salts. Sometimes, insoluable matter is added to prevent caking and these solid particles can become trapped in the film emulsion to form tiny white spots in the final print.

Since it is not easy to discern what is what, it is often best to stay away unless you are well trained in some aspect of chemistry or photography so that you can test for, or check your premise for a yes-no answer.

PE

See http://integrachem.com/grade.htm. Food grade appears to be higher than most others, next in line to analytical reagents.

Patrick, something may be chemically pure but contain an insoluable material. For example, Salt contains pure NaCl, but also is Iodized and contains Sodium Silicate. The salt is "pure" from a human consumption standpoint, but may not be for many photographic applications as we have discussed before.

You are adamant in your expressed opinions about chemistry, but I promise not to assist you in aerodynamics and human factors if you will believe me when I speak about chemistry! There are times when tables of purity such as you describe are faulty.

PE

A lot of food-grade, and alike, chemicals can be used for home brewing photo-products.
I am using them for years whit-out problems (till now), and buy them in professional cash and carry warehouses, to name a few :
Ascorbic acid -> patisserie
Sodium bicarbonate -> bakery
Sodium sulphite -> butchery
Sodium bisifite -> prepared meals
Citric acid -> patissery/brewery
Sodium hydroxide -> prepared and conserved fruits
Potassium hydroxide -> prepared and conserved vegetables
Soda -> soap
They all have a specific 'E' number and their quality/composition/application is regulated by the EEC.

Philippe

Alessandro Serrao said:

But you can always filter all particles out (I use coffee paper filters).
Reagent grade is way too expensive for me...

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Generally, photo grade is not reagent grade.

And, in some cases, the fines will go through a coffee filter. If the material forms a colloidal suspension, then it is probably too fine for your filter.

PE

Photo Engineer said:

Patrick, something may be chemically pure but contain an insoluable material. For example, Salt contains pure NaCl, but also is Iodized and contains Sodium Silicate. The salt is "pure" from a human consumption standpoint, but may not be for many photographic applications as we have discussed before.

You are adamant in your expressed opinions about chemistry, but I promise not to assist you in aerodynamics and human factors if you will believe me when I speak about chemistry! There are times when tables of purity such as you describe are faulty.

PE

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Adamant is not the word I would use to describe me. I have publushed formulas using salt, but I also specified uniodized salt, which is available at grocery stored. Canning salt also has no iodine. Vitamin grade ascorbic acid is also very pure. The grade I get from The Chemistry Store is not for human consumption, but still works quite well in photo use. Sodium bicarbonate from the grocery store is also very pure. I don't expect to find developing agents at the food store, unless you include Tylenol, Folger's coffee crystals and Vitamin C. Chesterton once proclaimed "We have passed from the age of common sense to the age of uncommon nonsense." If you want ademancy, look in a mirror. Meanwhile, please look at the web site I provided, you who want definitions of chemical grades.

Patrick, those salts may contain Sodium Silicate which is not good for film. Also, one person crushed Vitamin C tablets to get Ascorbic Acid, but those tablets contain an unknown percentage of filler which is usually starch. This changes the weight of AA present and also presents another rather insoluable material that might harm the film.

You keep ignoring these potential dangers over and over. That is my point. You are adamant tha they are safe and I am saying maybe and maybe not. Why take a chance?

PE

gainer said:

Adamant is not the word I would use to describe me. If you want ademancy, look in a mirror.

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gainer said:

Meanwhile, please look at the web site I provided, you who want definitions of chemical grades.

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Actually, Photo Grade is defined by standards orgaizations for several different photo chemicals but after looking into it years ago, I came to the conclusion that only the large scale manufacturer has the time and money to follow through with all the details involved... and that the only logical choice was to get the best quality I could afford.

I personally doubt the suppliers of chemicals (even if they advertise PhotoGrade) actually pay much attention to the problem, untill it becomes a problem anyway.

I myself ask for analytical data if it is not given, but it often is. But unless you know what you are lookng for it is just busy work for your supplier. Other than that, the best you can do is just keep an eye out for unusual behaviour... In fact, I have never had any problems myself, but the Chinese amidol might be an example of what can happen, even when one is trying to "do the right thing" but may not have the neccessary funds or knowledge to do so. Anyway, isn't that what using easy reach materials is all about? Trying to make do with what is available?

My take on this issue is that it is not optimal, but you probably could get away wth it, maybe even for a lifetime...

On the other hand, I would be much opposed to sending my film to a shop that admitted such practices!

Well, as one other person has said, to paraphrase him, we spend hundreds to thousands of dollars on a good camera and lenses and then buy the cheapest film and paper we can lay our hands on. And, if we mix up our chemicals from scratch, we do the same there. I just can't understand this philosophy and I cannot give advice that "might" cause a problem. I think that Ray's last 2 paragraphs say it very well.

I cannot recommend to you anything which I feel is not the very best and which might not live up to your expectations. I don't want you wasting your time and energy as well as the good money spent on good equipment and photo products on the chance you may get less than optimum results.

PE

The ascorbic acid tablets contain the amount of ascorbic listed on the label. The filler is extra. I tried it once to see if it worked. It did, but the resultant solution had a colloidal suspension of (probably) starch that could not be filtered out. I described all this in an article in Photo Techniques. For the person who has come near the bottom of cash reserves paying for camera and lenses, it may be useful to know that certain chemicals that are not analytical grade may be used with excellent results.

Some of my simplified formulas have enabled underprivileged children of New Zealand to experience the joy of photography, thanks to the efforts of Nicholas Twist.

Patrick;

Two things strike me here.

1. The person in question weighed the tablets and therefore was off in the amount of ascorbate by the amount of filler present. At least this is why and how I seem to remember it, and why it was pointed out.

2. In all of your comments, this is the first time that you have admitted here in your advice (AFAIK) that there is a non-removable solid in a chemical you are using. And, further, that chemical can lodge in swollen emulsion and cause spots by my reconing!

So, this uncertainty is what makes me reluctant to give the freewheeling advice you do. I strive for quality results through quality work. I won't take my film to be developed by a guy crushing Vitamin C tablets in the back room to mix his developer.

Thank you for finally admitting that there may be a problem in one of the routes you advise taking, and doing it here on APUG.

PE

gainer said:

Kirk, it would have been more helpful of you to remind an 82-year old where to find the previous coverage, which would also inform th OP and those who folloewd where to find it, than to admonish me for "digging up dead horses".

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OK - I'll save you time digging...

Here's a good one that it pretty specific to borax grades and purity;
(there was a url link here which no longer exists)

And another that goes that way:
(there was a url link here which no longer exists)

gainer said:

Food grade appears to be higher than most others, next in line to analytical reagents.

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Pat - that is a nice, general overview to chemical grades that you linked to. However, based on my knowledge of chemical grades, you are making a big assumption that the grades listed in that table are in any particular sequence of purity, i.e. ones listed further down the list are especially more or less "pure" than ones listed above, below, or adjacent.

The food industry world has different needs than the analytical chemistry world, and different needs than the photographic industry world. And so, the specifications of each use can be and often are different. Hence the different specifications for each industry. Sure, there may be some happy overlaps, but can you guarantee them all with your blanket statements? I do know of differences even between some photo and AR grade chemicals.

It says about Food Grade, "Food Grade is Integra’s line of high quality, economical chemicals suitable for use in food processing and production. They meet industry standard Food Grade specifications."

All this means is that it is suitable for the production of food AND it does not insure that it is suitable as a photographic chemical. High quality, sure, OK. But as has been pointed out many times in many threads, it may not be suitable in all areas for photographic use.

Pat, you have no basis for saying Food Grade is next in line to Analytical Reagents (AR grade). Have you examined the specifications of food grade compounds and compared them to AR or photographic grade specifications? Unless you have, you're simply guessing...

So I know you're going to reply, "try it, it works". Sure it "works". And as always, you are certainly free to do as you wish in regards to your film. But I really have to say that I liked Ray's post above about not wanting to take my film to someone that is using non-photographic grade chemicals to process my film.

I use food grade gelatin for carbon printing with great results...and have done so for around 15 years. So it might be worthwhile to use some food grade chems as subsitutes for a more pure grade...but a little testing is in order.

Vaughn

Vaughn said:

I use food grade gelatin for carbon printing with great results...and have done so for around 15 years. So it might be worthwhile to use some food grade chems as subsitutes for a more pure grade...but a little testing is in order.

Vaughn

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And that may be true for carbon printing but not for emulsion making. Also, you have to get the food grade without humectants and other addenda sometimes added to food grade gelatins. This includes carboxy methy cellulose and sorbitol among others.

PE

Photo Engineer said:

Patrick, something may be chemically pure but contain an insoluable material. For example, Salt contains pure NaCl, but also is Iodized and contains Sodium Silicate. The salt is "pure" from a human consumption standpoint, but may not be for many photographic applications as we have discussed before.

You are adamant in your expressed opinions about chemistry, but I promise not to assist you in aerodynamics and human factors if you will believe me when I speak about chemistry! There are times when tables of purity such as you describe are faulty.

PE

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Morton's canning salt has no additives. Intructions say to use this canning salt because table salt tends to leave a sediment.