Is food grade chemistry OK for use for photography?

[Photo Engineer]

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

Exactly my point and to the point of your post about Vitamin C tablets. Not everyone knows this though and as you suggested the use of Vitamin C tablets here earlier and now admit that a suspension forms in the developer due to the added filler, this represents the core of the problem and the potential danger.

It can create problems for people who are unwary or unaware of the potential problems in doing what you advocate. You say above "the resultant solution had a colloidal suspension of (probably) starch that could not be filtered out". And I say that this could have ruined film for someone unaware that this could be a problem and had taken your advice!

I am trying to get all of the facts out there so that people can make informed choices. You are dancing around your position in order to justify it. I'm saying that there are cases where it can blindside you and without proper knowledge you can ruin film by penny pinching in this manner.

Ray Roger's comment, "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! " is very apropos here!

PE

 

[gainer]

Patrick;


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

I admitted that long before I met you online, publicly, in articles in Petersen's Photographic and Darkroom and Creative Camera Techniques and its successor Photo techniques.

We all know that there are chemicals that will not be graded as a food simply because they are not foods or food additives. When it comes to things like Metol, Phenidone and its cousins, p-aminophenol, hydroquinone, catechol, pyrogallol, etc., we will not be buying them at food stores. Sodium bicarbonate is esilly converted by heating to anhydrous sodium carbonate of quite high purity because the bicarbonate IS considered a food additive as well as a medicine. What does that leave us that we could get as a food that we might also use as a photo chemical? Morton's canning and pickling salt is cheap and pure, with NO additives. I have mixed many 20 Mule Team Borax solutions and have never seen a sediment or any other indication of photgraphic impurity. In fact, 20 Mule Team Borax has been specified in at least one of my textbooks for use in D-76.

 

[Photo Engineer]

Patrick;

NaHCO3 -> Na2CO3 with heat, I grant you, but it also does this... Na2CO3 -> Na2O + CO2.

Then Na2O in any moist air does this: Na2O + H2O -> 2NaOH

Now, the exercise for the day for you is this. Please tell the inexperienced chemist how he knows he is converting Sodium Bicarbonate into anhydrous Sodium Carbonate or the more dangerous and higher pH Sodium Hydroxide? How does one tell, what temperature does it take place at, what is the degree of conversion...? Etc. bloody damn etc.... Did you warn them of this?

This simple reaction can also cause a fire if done in aluminum equipment. Did you tell them this? You have to remind your readers of this as well. What else have you left out?

PE

 

[alanrockwood]

PE and Pat,

Don't you ever get tired of fighting with each other?

How about give it a rest?

Alan

 

[Photo Engineer]

PE and Pat,

Don't you ever get tired of fighting with each other?

How about give it a rest?

Alan

Alan;

I would love to do that. But, you are begging the issue.

I am trying to give answers that supply high quality and Patrick is supplying answers that may or may not work, depending, and also imply a risk or liability.

So, you should make a stronger statement IMHO than just a simple one such as you did. Otherwise nothing is accomplished.

You have the opinions of several chemists and Patrick. The chemists seem to agree pretty much while Patrick, a non-chemist, has other opinions.

What do you think should be done? What would you do in a similar situation where someone is giving dubious suggestions? Don't cop out now....

PE

 

[alanrockwood]

Alan;

I would love to do that. But, you are begging the issue.

I am trying to give answers that supply high quality and Patrick is supplying answers that may or may not work, depending, and also imply a risk or liability.

So, you should make a stronger statement IMHO than just a simple one such as you did. Otherwise nothing is accomplished.

You have the opinions of several chemists and Patrick. The chemists seem to agree pretty much while Patrick, a non-chemist, has other opinions.

What do you think should be done? What would you do in a similar situation where someone is giving dubious suggestions? Don't cop out now....

PE

PE,

Speaking of chemists, I have a PhD in chemistry, and I find that both Patrick and you have interesting things to say, but when the two of you mix there is a lot of "bad chemistry" going on. One could take that several ways, and I invite all to do so.

Regarding the dissociation of sodium carbonate to make sodium hydroxide by heating the sample, yes it is possible, but not easy. Here is a link that discusses the problem.


http://books.google.com/books?id=NJ...=book_result&ct=result&resnum=1#PRA1-PA213,M1

Basically, it is not hard to dissociate sodium bicarbonate to produce sodium carbonate by heating the sample, but it is a lot harder to go the next step to produce sodium hydroxide by heating the sample.

 

[Photo Engineer]

Alan;

Thanks for the effort. Patrick and I have talked on the phone and agreed to disagree, sorry to say.

As for the formation of Sodium Hydroxide, I recognize what you say, but Patrick suggests heating on a stove over an open flame or electric coil with no temperature monitoring. As far as I can see in your reference, the situation refers to solutions of Sodium and Calcium Carbonate, but this is solid Sodium Carbonate that can go to any temperature your stove can supply unless you know what you are doing!

As for "bad chemistry", I have spent over 30 years in the lab and have seen Sodium Carbonate on a hot plate give off CO2 gas!

Now, the final question is this Alan. Given what I have stated here, and what Patrick has said, and factoring liabilities for accident or even just bad results with film processing, which do you wish to "assume" as your legacy to analog! I think you might alter your opinion when you consider the alternatives rather than the emotional one you express in your post. I do understand what you are saying though.

PE

 

[srs5694]

What do you think should be done? What would you do in a similar situation where someone is giving dubious suggestions? Don't cop out now....

How about you bookmarking previous threads on the topic and, when a post comes up that you disagree with, post a single link to whatever thread(s) you believe is/are relevant. Alternatively, put together a document that covers the issues and post it on your own Web site, and link to it whenever you feel it's appropriate. Either way will help avoid rehashing the same argument over and over and over and over and over and over and over and over again. Responding as you do just re-ignites the same tired debate. Posting a single link with a short sentence saying "I disagree, and here's why: (link)" would be less incendiary.

I don't mean to pick on you exclusively, PE; this particular dance requires at least two participants. Therefore, I offer precisely the same advice to Pat.

 

[Photo Engineer]

SRS;

Very good idea, but after multiple encounters here and on PN, I am truly getting tired. Imagine this. You are a surgeon who has spend a lifetime learning a complex profession and someone on the internet with a good education but in no way related to surgery is starting to give surgical advice.

How would you feel?

AAMOF, Patrick has just admitted that there is a potential problem which we identified years ago. Fillers in some cheap chemicals can harm your results. So, should I go on and on? I'm almost as old and tired as Patrick and have spent a lifetime in photographic science and engineering with a view to quality results. From my POV, he is a dilletante. Think on that for a bit and then come back to me with the references yourself. I really don't care anymore. You guys can use whatever crap you want to develop your films and papers. And, you take the responsibilty for the results. He takes the responsibilty for any accidents!

As Ray Rogers said, you might go for a lifetime with good results.... Or not!

PE

 

[srs5694]

I'm almost as old and tired as Patrick and have spent a lifetime in photographic science and engineering with a view to quality results. From my POV, he is a dilletante. Think on that for a bit and then come back to me with the references yourself.

It's your fight, not mine. Why ask me to dig up your references?

That said, Kirk Keyes posted two in an earlier message in this thread:

(there was a url link here which no longer exists)

(there was a url link here which no longer exists)

 

[Photo Engineer]

SRS;

I am fully aware of Kirk's post. Thanks though. And I understand your position and hope you will understand mine.

Best wishes in whatever road you take.

PE

 

[richard ide]

I find it very hard to believe that some people will use impure chemicals just to save a little money. There are enough variables in photography and photographic processes that introducing others is absolutely nuts. For example photo chemicals have minimal traces of iron present. Suppose that "food grade" has a harmless amount of an iron compound present for it's intended use but surpasses the limits required for photography. You have just introduced a potential problem. If a chemical I need is not available in photo quality, then AR is a quality I know will cause no problems and the analysis is on the label or easily accessible. Some products will cause no problems but one needs the background to make an informed choice.

 

[Sirius Glass]

I come here to learn about photography and get consistent results. Being told that I can do this or that and not being warned that doing either have problems or carry risks is being to less than useless information.

If one is going to make chemical recommendations then they need to disclose all the relevant information, not just the information that stokes their own ego.

Steve

 

[Kirk Keyes]

Like many other chemists I know (PE included), I find playing and tinkering with chemsitry a lot of fun. Even something like coffee-based developers have a place.

But I also agree completely with Richard Ide - for me and my photography, to entrust my hard earned photographs to anything less than photographic grade chemicals is something I find no value in.

And I appreciate Patrick's "back of the envelope" approach to engineering, I am also stupified by his appearant lack of appreciation of engineering specifications. That's what I find to be at the heart of these discussions - does one use materials that are designed for a specific use, or does one use materials that are superficially equivalent, ones that when pushed to the limits are not always completely equivalent.

A superfically nice looking house can be made using 1/4th inch masonite substitued for exterior grade plywood, 1x2s in place of 2x4s, or aluminum wire in place of copper. Sure, it looks like a house, it functions like a house, and it may last for some years, but when that first windstorm comes along, down it comes like a house of cards. Some may say that's still good enough, but I prefer things to be done a little more robustly. And so it goes with photographic chemicals, for me.

 

[Philippe-Georges]

Now the question is: next to the food grade what's the higher grade suitable for photography?

As an example (see attachment), here is the whole list of what one can find via one supplier for KBr, a rather 'simple' chemical in photography. I could not find it's counterpart of food grade, so I took the Ph. Eur. grade (ref. RdH 02110-500G-R), rather affordable for half a kilo...

Philippe

 

[gainer]

I don't recall leaving anything out in my original presentation. I specified Pyrex or stainless steel, moderate heat, which was to cease as soon as the little geysers quit forming. Furthermore, NaOH + CO2 => Na2CO2 which many of us who left the lid off the NaOH container have found. I told the readers to weigh the bicarb before and after heating and what change of weight to expect when the conversion was complete. I also suggested that a loose lid be put on the container while heating. Unless the hot NaO leaves the container, it will be in the presence of a CO2 atmosphere several times more concentrated than allowed for human habitation. The melting point of sodium carbonate is 851C which, IIRC, is about red heat.

 

[Photo Engineer]

Patrick;

Aside from the incorrect equation in your post, the melting point is indeed 851C, but the decomposition point is 400 deg C which is well within the reach of some here and might be achieved if the carbonate is unattended.

PE

 

[Vaughn]

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

You are 100% correct.

I would not use Knox Unflavored Gelatin (KUG) for something as exacting as emulsion making. Fortunately, KUG does not contain speedy cellulose D...sorry, but "methy" made me laugh, for which I thank you as I needed a chuckle!) nor sorbitol. At least it is not labeled as having those. And while it might be interesting to try to make a batch of carbon tissue using a flavored, sweetened and colored gelatin, I'll leave that up to someone else to play with.LOL!

But in the end, using food grade chemicals is a chancy thing...and what money one might save might be lost with badly processed film and loss of images.

Vaughn

 

[Photo Engineer]

I was eating hot mentos and drinking cola when I wrote that!

I have seen KUG both plain and with added ingredients listed on the side of the box. I have not looked lately, but those extra ingredients may have been removed. Certainly if it is unoxidized and non-photograde, it contains a lot of the sulfur containing amino acids such as methionine and others. It also degrades to release allyl thiourea during heating with water. It would probably also be high in calcium content due to the method of manufacture of ossein gelatin.

Anyhow... Thanks for the post Vaughn. My bad methy cellulose. When used correctly it is a moving experience.

PE

 

[alanrockwood]

Alan;

... As far as I can see in your reference, the situation refers to solutions of Sodium and Calcium Carbonate...

PE

No, the reference is not refering to solutions of sodium carbonate. The lowest temperature in the table for the dissocation of sodium carbonate is 700 Celsius. Water cannot exist as a liquid at that temperature. The critical temperature for water is 374 Celsius. Above 374 Celsius water is incapable as existing as a liquid, regardless of the pressure. Above that temperature it is what is known as a supercritical fluid, which is not liquid.

To give another perspective on that temperature, 700 Celsius is 40 degress above the melting point of aluminum.

 

[Photo Engineer]

Well Alan, sorry I misread the table then. You must be a Physical Chemist and I'll admit to being a lowly Organic Chemist.

At the bottom of that page you refer to, it talks about the conversion percentages of various concentrations of Sodium Carbonate solution and the use of Calcium Hydroxide to give certain percentages of Sodium Hydroxide. This infers to me a conversion in solution and the ability to draw down Sodium Hydroxide from such solutions, but I was not exactly sure what you referred to when the article talked about solutions and calcifications and how it related to our discussion here. After all the soda lime process has been known for several centuries and this is what was being described in the text as a way around direct heat conversion. Direct conversion is possible according to the article and you give a value of 700 C while my table gives 400 C.

Above the table, it says that forming Sodium Hydroxide by heating Sodium Carbonate is possible but not recommended. Which, of course, I agree with and was referring to myself.

Going back to the table I have, it gives a decomposition temperature of 400 C for Sodium Carbonate. This is about 20 deg cooler than the melting point of Zinc. It is also about 1000 degrees below the melting point of Iron and also about 300 degrees lower than the melting point of Aluminum. So, at red heat in an ordinary Aluminum or Iron pot, from the data I have at hand, I think that Sodium Carbonate can begin to decompose at the red heat of the electric coil on an electric stove if left unattended or if being improperly attended.

I have to stand by saying that it is a bad idea to heat Sodium Carbonate hydrates on a stove in a pot to drive off water and make the anhydrous salt by guess and by golly!

I think that Kirk's house analogy is very much to the point here.

PE

 

[gainer]

All this without having read my original article in Photo Techniques (It was darkroom and Creative Camera Techniques then).

The mistake in the equation was obviously a typo.

It is not necessary to reach 400C to make the carbonate. Aluminum melts below red heat. One can tell when the process is complete simply by the feel. When agitating the pan of bicarbonate by swirling motion, as long as CO2 is being omittted, it feels like swirling a pot of liquid. I am not exactly uneducated in chemistry. I started in Chemical Engineering at WVU and switched to Aeronautical Engineering after my third year, having made good grades in qualitative and quantitative analysis.

It is in fact my opinion that one should not have blind faith in the purity classification of any chemical. The tests that provide these classifications can only be made on random samples of the particular chemical. If you are using a bucket of the chemical, it may or may not have the actual charactristics of the tested samples. If there is even a small variance in those samples, the relatively tiny sample you select may have as much as three times that variance. The appropriate test is using it in the procedure you intend to use it in. PE has uses for certain chemicals that are more sensitive to certain impurities that would hardly be noticed in my photographic life, which is already 70 years old. As an experienced photo chemist, he surely can test every chemical he plans to use, and really should do so rather than rely on another's grading process.

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.

 

[alanrockwood]

Well Alan, sorry I misread the table then...

...This infers to me a conversion in solution and the ability to draw down Sodium Hydroxide from such solutions, but I was not exactly sure what you referred to when the article talked about solutions and calcifications and how it related to our discussion here....
PE

I probably should have been more clear in stating that I was referring to table 7-5 for the heating of the dry chemicals.

 

[Kirk Keyes]

It is in fact my opinion that one should not have blind faith in the purity classification of any chemical.

Well, that's why these things are tested in order to become graded. And you don't need blind faith with Analyzed Reagent grade as you can get a certificate of analysis of each production lot if you wish.

 

[Kirk Keyes]

The tests that provide these classifications can only be made on random samples of the particular chemical. If you are using a bucket of the chemical, it may or may not have the actual charactristics of the tested samples.

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!