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 10:23 AM. Click to view previous post history.
Could you at least take the time to define "trivial both in content and in testing"? I have a feeling that if you were to take the time you might find that 20 Mule Team Borax would pass the tests. There is no specific requirement for Chloride or Sulfate. I found it surprising that passing the carbonate test means that carbonate is less than about 1%.
Originally Posted by Photo Engineer
The foreword states that "This is one of a series of standards that establishes criteria of purity for chemicals used in processing photographic materials."
I'm of the opinion that what you are really saying is "Don't confuse me with the facts. My mind's made up."
I'm not saying you should use any particular brand or grade of anything. The cheap stuff does pass the test for iron. Whether its content of chloride and sulfate would cause it to fail the ammoniacal silver test, I do not know. Perhaps you could inform us on the basis of known specs in what ways the best is better than the technical powder for processing film.
All right, I'll describe trivial in testing first.
Carbonate test, add sulfuric acid to a measured amount of borate solution and if it fizzes it fails the test but if it does not, it passes. That is my definition of a trivial and rather useless test, chemically.
Trivial in content now. Halides and heavy metals are critical in some applications and these are not addressed fully, just a few as seen from your post. As far as solids are concerned, a visual inspection is all they ask for. This is trivial both chemically and in content or intent for the purpose at hand, which is photography.
Does that mean that you have in fact tested "the best" by those more stringent tests, or that you just don't trust the Photographic & Imaging Manufacturers Association, Inc. to know what is suffucient for film processing? You must have, at some time, tested 20 Mule Team Borax and "The Best" if you are so sure about the differences in purity.
Originally Posted by Photo Engineer
I have run qualitative and quantitative analyses on many materials. I would say that these are qualitative in nature and are not indicative of much. Also, as you mention in the original post, these are ANSI. Are they PMA as you now state? PMA does not define standards AFAIK. ANSI and ISO define the standards that Kodak uses.
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I've been thinking of a different tack here. This is about Borax and developers but lets define Borax for all photographic uses.
It is used as a buffer in fixes as well as in developers. Now, we know that Potassium ion will 'poison' a fix. This is stated unequivocally in Mees, Mees and James and Haist. Therefore, for photographic use, a Borax buffer would have to include Potassium level as part of its specification.
Do you see my logic about looses specification and specifications intended for photo chemical use?
The printout I got says at the top that it was approved 2/20/82 and reaffirmed 5/12/98. Secreteriat: Photographic & Imaging Manufacturers Association, Inc.
It is part of a series of chemicals used for processing photographic materials. None of the grades of borax that I have seen specs for have even mentioned Potassium, and I have seen a lot of them in the past few weeks, including pharmaceutical grade. Did you really get a guarantee of no Potassium? How would we know where to get the "best stuff"? I see your point about specifications. I have not seen how you know you have satisfied your needs. Do you know for a fact that your borax has been tested for Potassium?
The ANSI Standard claims only to imply a consensus of those substantially concerned with its scope and provisions. It further states "Although the ultimate criterion for suitability of a photographic grade chemical is its successful use in an appropriate photographic use test, the shorter, more economical tests described herein are generally adequate.
It would be a good thing if instead of saying that what would keep one from using the technical grade as specified by the manufacturers must necessarilly keep one from using it for any photographic purpose, to tell us what we more mundane uses we might put it to in the darkroom, especially since that grade has passed the use test over many years in many different developers.
Lots of typos. Not much sleep last night. Sorry.
Pat - I broke down and got the specification yesterday as well. But I only had to pay $17 from ANSI online!
Originally Posted by gainer
They are trivial tests! Nessler tubes in fact. (You have to work at a lab that has been in business for many decades to find a set of Nessler tubes. BTW, I just found a set of Nessler tubes in the lab last week!)
And I too was disappointed that ANSI was not more interested in the specific analytes we've been debating about for the last few weeks.
So I think the lesson to be learned here is found in the second paragraph, right after the line you quoted above:
"Although the ultimate criterion for suitability of a photographuc grade chemical is its successful use in an appropriate photographic use test, the shorter, more economical tests described herein are generally adequate."
What that tells me is that the ANSI spec is generally sufficient to descriminate between a grade that is useful in photography and a grade that is not sufficient for use in photography.
But, as PE points out, the real test is will the material work in the desired use. Buying a better grade than technical, like the NF (National Formulary) grade or especially the SQ which is very low in chloride, sulfate, and iron, guarantee that it would be suitable for all photographic purposes. (See http://www.borax.com/products1.html to find info on the grade Pat has been talking about.)
The only catch here is the SQ is a nuclear grade and is used for quenching runaway nuclear reactions. I but you would pay through the nose for that stuff. And no wonder it's so clean - you don't want to crap up your nuclear reactor with regular mule crap!
So did out those dusty, old Nessler tubes and get testing on your 20 Mule Team tech grade and show us that it does past the ANSI spec. I think it might pass all but the "reaction to ammoniacal silver nitrate" and maybe the "Appearance of solution" test. And that last one you can certainly do and let us know.
PS - if you need a set of Nessler tubes, here's some on eBay right now:
http://cgi.ebay.com/NIB-12ea-Nessler...sid=p1638.m118 only $15 for 12 plus shipping.
Last edited by Kirk Keyes; 12-28-2007 at 12:26 PM. Click to view previous post history.
We all know from watching the various CSI shows on the boob tube that identification of microscopic traces of anything is now a piece of cake.
A saturated solution of MC is clear as distilled water. I have no idea how much chloride-bromide it takes to fail the ammoniacal silver nitrate test. I am quite sure that a higher grade would be required for analytical work, but I'm also quite sure from my own long experience that for use in film and paper developers, MC is fine.
Now PE has thrown a new monkey wrench into the works. What if there is potassium in the MC and I want to use it to make fixer? First, I looked all through my copy of The Theory of the Photographic Process and could find no admonitions or even mention of the effects of potassium in fixer. Maybe there is a later edition than the third, but I think they would have known about it by then. But suppose we must avoid potassium in the fixer at all cost. How would it be removed from borax, especially if it is in the form of potassium tetraborate? Also, how much washing between developer and fixer would be required to prevent carryover from a potassium-containing developer, of which there are many? Perhaps PE was referring to color developer.
I must repeat my request that you guys also test what you buy to make sure you are getting what you think you got. I have used MC long enough to know it does what I expect of borax, but have you used it long enough to know that it does not do what you expect of it, or tested yours against MC to see if you could use it?
Last edited by gainer; 12-28-2007 at 01:03 PM. Click to view previous post history.
Mees, P 719, Mees and James, P 400 and Haist, Vol I, P 566 in which he states that fixers with Potassium salts are virtually useless. (Work of Frank and Schramm). Mees shows that K salts are roughly 4x slower as fixing agents.
So, I have found it in 3 places, besides having worked with Grant and others on some of this stuff.
Using Potassium Metaborate as a buffer in a fixer could paralyze its activity. A high percentage of potassium in Borate salts used to buffer a fixer might also slow it down or cause bad fixing.
A good stop or wash after a potassium containing developer will do a good job in preventing deterioration of the fix, but a standard test of the fixer will show either clearing time going up or silver halide being retained. Since we all check our fixer quality, this should not be a problem, right?
Patrick, you are questioning me on my home turf when you talk fixers! I learned from these people and many of the people that they refer to when I started at Kodak.