Experiments with Metol and ascorbic acid.
The factors affecting developer activity are temperature, pH,
concentration, products of aerial oxidation, products of silver halide
reduction, and the orientations of the heavenly bodies.
According to some experimental results reported in "The Theory of the
Photographic Process" as little as 0.05 moles (6.3 grams) of sodium sulfite in
a liter of Metol developer will double the rate of development that is
obtained when no sulfite is present, pH being held at 8.7 in both cases.
It is explained that oxidation products of Metol restrain development, and
that sulfite counteracts these products by forming the sulfonate.
Ascorbic acid will do the same degree of acceleration without sulfite, also at pH 8.7. In this case the oxidized Metol is reduced back to its original form. The ascorbate is itself oxidized and pH is decreased in the process. The decrease in amount of active Metol in the one case or the decrease of pH in the other may not cause much difference in capacity and storage longevity between a Metol-sulfite and a metol-ascorbate developer. However, it would seem that a well buffered working solution might tip the balance in favor of the ascorbate.
I will explore first a 0.05 molar concentration of Metol, which is
approximately that of D-23, together with a 0.05 molar concentration of
ascorbic acid. It remains to formulate the alkali needed to make the pH less
than that at which an ascorbate becomes a developer and great enough to ensure activity of Metol.
I calculate that 0.1 moles of sodium hydroxide will neutralize the 0.05
moles of sulfuric acid attached to the Metol base plus the 0.05 moles of
ascorbic acid, leaving 0.05 moles each of sodium sulfate and 4-(methyl-
amino)phenol and 0.05 moles of sodium ascorbate. The net pH thus far is still
not alkaline enough to develop film in a reasonable time, nor does it have the
necessary buffering action to keep the pH from going lower yet. A few grams of borax should bring the pH up to about 9.2 but even 20 grams will have little
more effect on pH and should give a cushion against reduction of pH during
The resulting recipe is:
Ascorbic acid.....8.8 g
Sodium hydroxide..4 g
Water to 1 liter.
The concentration of Metol is about 13% greater than in D-23 and the
concentration of sodium sulfite is nil.
The pH of this mixture, which I measure with test strips to be about 9, is
below that at which the ascorbate is a developer of any consequence. The
initial activity of the mixture is about that which could have been obtained
with sulfite in place of the ascorbate, so it does not seem that synergism
between Metol and ascorbate is the explanation.
The ratio of borax to caustic in this formula is quite close to the
effective ratio in sodium metaborate. 14.5 grams of sodium hydroxide and 69
grams of borax in a liter make a solution that is often used as a substitute
for 10% sodium metaborate. 276 ml of such a solution, or 27.6 grams of Kodalk if you prefer, will contain the equivalent of 4 grams of sodium hydroxide and about 20 grams of borax. It may be easier to get sodium metaborate than sodium hydroxide through the UPS. The recipe then becomes:
Ascorbic acid......8.8 g
Sodium metaborate..27.6 g or 276 ml of 10% sodium metaborate solution.
Water to 1 liter.
All ingredients are quickly dissolved in room temperature water. HP5+
developed for 8 minutes at 68 F gives normal contrast, showing that the
solution could be diluted. In fact, diluting with an equal part of water
increased development time by only 25%, probably because the pH of this
solution does not change much with dilution. 125 ml diluted with 125 ml of
water did a 36 exposure roll of HP5+ to normal contrast in 10 minutes, which
means of course that a liter of the above formula will do 16 standard rolls
without reuse. As a matter of interest, twice the above recipe can be squeezed into one liter.
By the way, don't be confused by the fact that there exist 4 mol and 8 mol
metaborates. A gram of one has the same number of atoms of sodium, boron,
oxygen and hydrogen as a gram of the other. At 53.6 C, without losing any
water, Na2B2O4.8H2O becomes NaBO2.4H2O which is stable to 105 C. In other words, the distinction between 4 mol and 8 mol sodium metaborate is academic, not practical when we specify solution strength in terms of weight per unit volume. You may see this for yourself at www.borax.com.
I am attaching a scan of a 10x print from FP4+ developed 8 minutes, 68 F. This is not of very high resolution, but may serve to illustrate gradations. I have also attached a higher resolution scan of a small part of the same print. If you print the high res. scan to 6x9 inches, you will see about a 50X magnification of that part. I have no idea how these will show up, but you can imagine that the originals are better.
As it turned out, the attachments showed up at the end of the thread on superadditivity started by PE. My fault.
Last edited by gainer; 06-03-2007 at 11:23 AM. Click to view previous post history.
Now on to your second paragraph. Indeed Potassium Alum is used in fixes and it slows down fixation and causes silver retention. This is why hardening fixes began using ammonium salts to take into account the synergy between thiosulfate and ammonium ion. In effect, you can balance out the effect of potassium but only to some extent. Elimination of the potassium will allow even faster fix rates and better fixation.
As for the use of borax in fixers, they are used in many alkaline fixers as a buffer. If the level of potassium were to be too high, it would negate the effect of having an alkaline fixer entirely and make it as slow as an acidic fix of much the same formulation. Washing would probably be slowed as well.
As far as having references here, yes I do. I have hundreds of textbooks on photographic emulsion making and processing, books on theory and books on system design. So, when I wrote that note giving references, I had 3 textbooks open next to me to those pages reading exactly what was said.
And, I have done lab experiments, some of them with Haist standing next to me either guiding or observing, invovling these processing principles.
And, since we have no spec for potassium in tetraborate or boric acid in the standard you published, we don't really know how it would work in some instances.
So there is no further doubt about potassium salts in fixers, here is the passage from Haist.
I don't even remember how this got into a pissing match. All I wanted was some clear idea why 20 Mule Team Borax was not as good as so-called photo grade for my purposes and those I propose. I could get no specs for whatever grade you use for allowable soluble impurities. I could find lots of guaranteed specs for sodium tetraborate pent- and decahydrate, but never got an answer as to which one you would accept for practical use in developers. I have never proposed a formula for a fixer. I have never proposed a developer formula that I have not used myself. Until recently, I never used significant quantities of borax that I told anyone about.
I do not understand why I am accused of confusing others and am told to keep my nose out. You are the one telling others that 20 Mule Team Borax has impurities that keep it from being properly used for developers without telling them what to use in its place except to get it from a photochemical dealer, also unspecified, who might in fact be repackaging the same produce you get in the grocery store.
When I proposed a way to reduce soluble impurities by a factor of 16 or more you had a lot of "Yes, but"s. I think that AR grade is an unnecessary cost for most of us, and that for most of us who might want a small amount of more pure borax, the differential solubility method will work quite well. As I said, I did quite well in the Chemical Engineering Lab course. I was simply unable to handle courtship, being principal oboist for the University-Community Orchestra, and a 21 credit hour course load including the seond semesters of both Physical and Organic Chemistry lecture and lab courses all at once. I was not the first, nor the last to have that happen. I could have repeated Organic chemistry but chose instead to change to Aeronautical Engineering. If that makes me an idiot, then at least I am a well educated idiot.
Photo Engineer;565289]"Now on to your second paragraph. Indeed Potassium Alum is used in fixes and it slows down fixation and causes silver retention. This is why hardening fixes began using ammonium salts to take into account the synergy between thiosulfate and ammonium ion. In effect, you can balance out the effect of potassium but only to some extent. Elimination of the potassium will allow even faster fix rates and better fixation."
I never proposed the use of potassium salts in any fixer.
"As for the use of borax in fixers, they are used in many alkaline fixers as a buffer. If the level of potassium were to be too high, it would negate the effect of having an alkaline fixer entirely and make it as slow as an acidic fix of much the same formulation. Washing would probably be slowed as well."
IIRC, I asked what would borax be doing in an acid hardening fixer.
"As far as having references here, yes I do. I have hundreds of textbooks on photographic emulsion making and processing, books on theory and books on system design. So, when I wrote that note giving references, I had 3 textbooks open next to me to those pages reading exactly what was said."
OK. I believe you. But it still remains difficult to see how trace amounts of potassium chloride or even potassium borate apply to those comments.
"And, I have done lab experiments, some of them with Haist standing next to me either guiding or observing, invovling these processing principles.
And, since we have no spec for potassium in tetraborate or boric acid in the standard you published, we don't really know how it would work in some instances."
I didn't publish it, I repeated it from the ANSI-PMA Standard for borax for photographic use.
Ridicule is the lowest form of argument. Argument from authority is not much higher when other bases are available.
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You asked why I thought that the standard you published for Borax was trivial and useless for photo products. I pointed to the fact that it had no standard for presence of potassium salts and was therefore unsuitlable for application to fixers.
You questioned the authority on fixers and indeed the use in fixers, or in fact, any problem with the use of potassium alum in fixers.
So, I iterated the problems and gave the literature references which you also questioned. Then, I posted the data from the reference itself.
So, by line chapter and verse, I have tried to point out the error in the poor standard you posted, and you replied with what was essentially "yes, but" or "I can't find a reference".
So, that is how this took place. I questioned the standard and stated my reasons for both developers and even more importantly for fixers. You refused to accept my answers as being either factual or correct, and so I gave instances to prove my case.
No, the problem was not my refusal to accept answers, it was my refusal to accept your interpretation of the problems. I am quite sure you provided accurate answers to the problems you posed, but they were not all the problems I wanted solved. If you had from the start identified your source for the borax you recommend and a set of specifications for it so that anyone else could search for other sources of equal product, I would have been happy. I still might have proposed a way to make cheaper product work for special occasions, who knows?
As it happens, all the impurities you have supposed might be in what I now fondly call "Mule Crap" are either very much more soluble than borax or insoluble. That includes all the likely potassium compounds. That means they may be reduced by the method I described to whatever percentage might be desired by successive solution and filtering. If you use the last solution as the product, you can dry it to powder if desired or use it as a known percentage solution. Now if I just knew the specs you require for your particular work, I could devise an engineering approach to providing it from cheap stuff and you could decide whether it is worth the trouble. I should remind you that the high quality stuff is not always available in small quantities, so you might have to buy a 50# bag to get a few ounces.
I'm going to lean back, relax, and let you teach us all chemistry. Have fun.
In the meantime consider whether you are doing a real service to quality photo processing or are merely putting a means into peoples hands to play around with by your use of pool and laundry chemicals and the use of volumetric measure of solids.
Remember, if some newcomer to photography follows any of your advice and gets a bad result, you may discourage him from continuing. This is the responsibility that I feel with every post I make.
There are two levels here, fun photography to see what can work, and serious photography in which we want a good, repeatable process.
I can tell you what must not be in Borax except in very tiny trace amounts.
Insoluable materials (dirt, sand and etc...)
Those are at the top of my list and should be absent from good Borax. And, high quality stuff is always available in small quantities. I can get 100 - 1000 grams of analytical or reagent grade Borax any time I wish. It is available on-line.
I have tried to tell you that I did NOT publish the ANSI-PMA standard. I did not question the literarure references except to note that one of them is not in my copy of the third edition of "The Theory....." on the page you quoted or anywhere else. And it has not appeared there by some miracle since then. And instead of replying with the date of printing of your copy, you chose to ridicule my intelligence and my knowledge of chemistry. I'm sure your copy has a later printing date than mine, which is the fifth printing of the third edition.
Originally Posted by Photo Engineer
I don't mind your questioning of the ANSI Standard, but please don't blame me for it. It specifically applies to most common photographic uses, and has more disclaimers than the stuff that is supposed to make a utility pole out of a penis.
You didn't publish them?
Originally Posted by gainer
What is this?
And I called the tests and specs trivial and meaningless after that post, and then things were off and running.