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.
Quote:[Patrick; Any biochemistry text will draw chemical reactions with circular arrows for each reactant. Things keep cycling each other. With an ET developer, it can either recycle both ingredients or have one 'pump' the other in activity.]
I have known since high school that if it is possible for the ingredients of a solution to form more than one set of compounds, they will be formed given the right conditions. Of course, if you want a particular set of compounds to be formed you have to know the conditions. I make prety good coffee because I know the right conditions to avoid the "fusel oils". Whether or not that is what they really are, I don't know
I have found that the activity of the p-aminophenol-ascorbate developer is not greatly diminished by using 0.01 moles of p-aminophenol, 0.05 moles of ascorbic acid and 0.06 moles of sodium hydroxide plus 10 grams of borax. The borax and sodium hydroxide may be replaced by 16.7 grams of sodium metaborate. Thus the recipe becomes:
ascorbic acid................8.8 grams
2.4 grams sodium hydroxide + 10 grams borax
sodium metaborate........16.7 grams
Water to 1 liter.
FP4+ for 8 minutes at 70 F will still be sufficient for most purposes.
I forgot to say that the above recipe is for the working strength solution.
Still the best and easiest to mix is the phenidone-ascorbate in water. Phenidone is less sensitive to bromide content than just about anything other than (perhaps) amidol. That means that it will make a long lived developer in a self replenishing system. The aerial oxidation in such a solution is to the ascorbate and its product is acidic, but the acidity is minimized by the buffering action of the borax. A liter of working strength, reusable developer can be made from 0.8 grams of phenidone, 10 grams of sodium ascorbate and 10 grams of borax. Note that the phenidone is at half the strength of the original formula.
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If it is easier, you may use 8.8 grams of ascorbic acid + 4.2 grams of sodium bicarbonate. Mix it in a little warm water and let the effervescence subside befor adding the phenidone and borax.
Don't even bother with the bicarb. 0.8 grams phenidone, 9 grams ascorbic acid, 25 grams borax and water to make a liter will do the job for either film or paper. If you keep your phenidone in a glycol solution, you can mix a batch in just a few minutes. You will probably want to dilute the stock for use. I'll come back when I can give more information.
FP4+, 6 minutes, 70 F; 7 miuntes, 68 F. Normal contrast, no problem with box speed + or - 1/2 stop.
Sorry, I didn't do exactly this, but I did do two things that proved to my satisfaction that my MC-TEA only needs more alkali to activate it, and that sulfite doesn't have any particular role in getting the metol-ascorbic acid synergy going.
Originally Posted by gainer
Instead of adding two teaspoons of sulfite to a liter of working solution I added two tsp sodium metaborate. The resulting developer was extremely active, developing Delta 400 to a contrast index of 1.9 in the same time it takes the sulfite mixture to get to 1.2. However, shadow detail was very poor, so I'll stick with the sulfite formula for now (especially since I have 5 lbs of the stuff).
I also tried using double the amount of sulfite (but no metaborate), which gave me about the same development time as the original amount.
If you should want to use acetaminophen (Tylenol) in place of p-aminophenol, the 5.45 grams of p-aminophenol will be supplied by 7.5 grams of acetaminophen or 15 of the 500 mg tablets. If you use the tablets, crush them to a powder. Add 1/2 teaspoon of ascorbic acid and 1/4 tsp of sodium bicarbonate to 40 ml water, let the effervescence subside and then add the acetaminophen and 4 grams of NaOH or 5.6 grams of KOH. Stir well and let it stand a while. Bring the water up to about 700 ml and add 2 teaspoons of ascorbic acid and 2 tablespoons of borax. Add water to make a liter.
You will probably have to dilute this developer at least 1+4 to make it managable. The best way to dilute these developers is to add more of the ascorbic acid-borax mixture. You can make 4 liters of it with 35 grams of ascorbic acid and 100 grams of borax. This way you need not worry about whether you will have enough of the developing agent in the working solution when you try such outrageous things as stand development for an hour with 1:50 dilution of the working solution. There will be as much of the ascorbate in the diluted solution as in the full strength, and that will ensure that the p-aminophenol or phenidone is continually regenerated. This is a chance to see if the usual statements about starved development and characteristic curves, Mackie lines, etc. are pertinent here.
Last edited by gainer; 08-03-2007 at 07:46 PM. Click to view previous post history.
Found another source of borax. Had only been able to find 20 Mule Team, and at last one source of that.
Pool supply stores have been referenced for hypo/fixer but hard to confirm actual product contents per some readers.
Here's one borax source:
NOT "Supreme Plus" - that has additional components, boric acid and fragrance. Still costs more than 20 Mule Team - strange that this is the case.
While I'm here, the same company has a sodium thiosulfate 'ChlorOut' product.
Haviland Chlor Out - I found MSDS(to confirm contents) the other day with alot of searching, but not tonight. Their web page will let you bring up Chlor Out for shopping basket but no MSDS - can't verify it's a current product. Lots of discounted 2# bottles on eBay, however.