Experiments with Metol and ascorbic acid.

gainer · Jun 2, 2007

gainer submitted a new resource:

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

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

craigclu · Jun 3, 2007

Your scans weren't attached, Patrick.

How did the negatives perform, photographically? Do you have a sense of curve shapes yet? I've had nice results with my equipment and techniques with metol-based concoctions lately so this caught my attention.

Thanks again for your energy and expertise in these matters!

gainer · Jun 3, 2007

craigclu said:
Your scans weren't attached, Patrick.

How did the negatives perform, photographically? Do you have a sense of curve shapes yet? I've had nice results with my equipment and techniques with metol-based concoctions lately so this caught my attention.

Thanks again for your energy and expertise in these matters!

My attachments got attached to the end of the superadditivity thread started some time ago by PE. My bad. You can see them there.

I like the results very well. Metol-ascorbate has a little advantage over phenidone-ascorbate in that Metol has more tanning action. The relief effect seems to make edges a little different due to the diffraction. I have done essentially this same thing using phenidone, but cannot dissolve 0.05 moles of it. 0.01 moles, 1.62 grams, of phenidone substituted for the Metol is quite potent, however. Only half the hydroxide is required since phenidone has no attached acid molecule.

psvensson · Jun 4, 2007

Interesting formula, but there seems to be a lot developer relative to the activity! By comparison, I use a version of MC-TEA plus sulfite that has approximately the following amounts in the working solution. It is slower than the developer you describe here, but not in proportion to the amount of developing agent. Without sulfite, this developer does practically nothing.

1l water
metol 0.3g
ascorbic acid 1.9 g (actually C-1000, health-food store version that is about 40 percent less active than pure ascorbic acid)
triethanolamine 8.3ml
sodium sulfite 10g

Delta 400 35 ml 75F 14min.

psvensson · Jun 4, 2007

Hm, looking at all the components in two developers, not just the developing agents, they're not that different. The formula on top is about 40 grams of stuff in a liter of water, mine is 20g. And my development time is probably 70 percent longer.

gainer · Jun 4, 2007

It is possible that the difference in pH is enough to stimulate synergism. I have had developers with about the ratio of Metol-ascorbate without sulfite but with carbonate that are very active. Around pH=9 which you should get with borax in place of the TEA you might find you don-t need the sulfite. The research I based my experiment on used 0.05 moles of ascorbic acid at pH=8.7. I have to go now. Will return.

gainer · Jun 4, 2007

My purpose in these experiments was to get a practical feel for the results I saw in "Theory of the Photographic Process". Sometime I feel that there might be an advantage in a "thick", less active developer over the thin but very active ones we see a lot of now. My idea was one that would be more or less self replenishing. Phenidone would be a better candidate for that because of it lower sensitivity to bromide build up.

The pH is between 9 and 10 according to my test strips, and it won't change much with dilution because there's a lot of borax in there.

I'm still trying to figure out what you have. There may be as little as 4.5 grams of TEA in a liter that is not neutralized by the ascorbic acid and the sulfuric acid on the Metol. I have a table that tells what pH one might expect.
It says 4.5 grams of TEA/100 ml of solution should give a pH about the same as borax. You have only about 1/10 that amount. It would be a good thing to know if the sulfite was acting as sulfite or just as extra alkali. You could try using 10 grams of borax instead of the sulfite to see what happens.

Cheers,
Pat Gainer

gainer · Jun 5, 2007

Another point is that the curve from Mees & James shows that the effect of either ascorbic acid or sodium sulfite increases as mole fraction rises to about 0.05, then levels off with further increase. Thus 10 g/l sulfite is well above that point while 1.9 g/l even of full strength ascorbic acid is far below. If you were to bring the ascorbic acid up to 8.8 g/l (as an ascorbate, of course) you might see the activity increase without sulfite. However. I don't think you have quite enough pH without the sulfite. It should be about 9.

I have a feeling that it is the molar concentration of either the ascorbic acid or the sulfite that counts, not the ratio of either to the Metol, as long as the pH is right.

psvensson · Jun 5, 2007

Yes, I'll try adding more TEA instead of sulfite and see where that gets me. I concocted this mixture to save on TEA, the only ingredient I can't obtain close by.

psvensson · Jun 5, 2007

Here's the thread Patrick is referring to:
(there was a url link here which no longer exists)

gainer · Jun 5, 2007

While you are about it, add 8.8 grams of ascorbic acid and 6.6 ml of TEA to the liter of working solution without sulfite and check the activity.

Meanwhle, I cut the Metol to 0.01 moles /liter (3.44 grams), used 8.8 grams/l of ascorbic acid and 16.6 grams of sodium metaborate, and the activity is almost what it was with 0.05 moles of Metol.

gainer · Jun 6, 2007

I'm ashamed to say it, but 8.5 grams of Metol are 0.025 moles, although the resulting solution contains 0.05 moles of 4(methyl-amino)phenol after the sulfuric acid has been separated. The 3.44 grams actually make 0.02 moles of 4(methyl-amino)phenol. By some bit of luck, or maybe my brain was working then, I got the amount of hydroxide right so the solution pH is as close to 9 as my pH strips will tell me.

I found that the developer using phenidone gives about 1 f-stop more film speed, although I used the box speed with the Metol version and got good shadow detail. I guess the phenidone version would be good for unavailable light.

gainer · Jun 6, 2007

I'm not entirely sure about that difference in speed. A difference in fog density can look like a difference in speed at first glance.

gainer · Jun 10, 2007

This is copied from the post on edge effects. Mix 1/2 teaspoon of Phenidone with a little isopropyl rubbing alcohol to make it easier to dissolve in water. Mix a couple of ounces of water, 2 teaspoons of ascorbic acid powder and 1 teaspoon of sodium bicarbonate and stir til the effervescence subsides. Warm it slightly to get more CO2 out. Add this mixture, the Phenidone, two teaspoons of borax and enough cold water to make 1 liter. Use it full strength or diluted as you would use D-76. At full strength it can be reused for at least 8 36 exp. or 8x10 films. All the teaspoon measures are levelled standard cooking measuring spoons.

gainer · Jun 18, 2007

Now let's play with p-aminophenol.
Paraminophenol is not very soluble in water. The potassium aminophenolate is quite soluble and a very active developer. Before we knew it as the proprietary Rodinal, Hurter and Driffield referred to a developing agent named rodinal, which I think might have been potassium aminophenolate. We can make a 0.05 molar solution of this rodinal from 0.05 moles of potassium hydroxide and 0.05 moles of p-aminophenol base, add to it 0.05 moles of ascorbic acid and another 0.05 moles of sodium or potassium hydroxide and some borax and end up with a kinder and gentler Rodinal expedient. Maybe.

This recipe is:

5.45 grams of p-aminophenol base
8.8 grams ascorbic acid
28 grams of sodium metaborate
Water to 1 liter.
( the 28 grams of metaborate includes the equivalent of 4 grams of sodium hydroxide and a bunch of borax.
I doubt that you will want to use this stuff full strength.

You can make a 2-part concentrated developer as follows.

Dissolve 22 grams p-aminophenol base and 35.2 grams ascorbic or erythorbic acid in about 400 ml propylene glycol. Add glycol to bring volume to 500 ml. This is solution A.
Dissolve 110 grams of sodium metaborate in water to make 500 ml. This is solution B. If you do not have metaborate, use 16 grams of sodium hydroxide or 22 grams of potassium hydroxide plus 76 grams of borax
Mix equal parts of A and B in water. A typical dilution would be 1:1:25. A typical development time for FP4+ would be 8 minutes at 70 F.

Photo Engineer · Jun 18, 2007

If the ascorbic acid were regenerated, then this would be an electron transport developer. Unfortunately, if the other agent is consumed, it is not an ET developer. It is superadditive though.

PE

gainer · Jun 18, 2007

Photo Engineer said:
If the ascorbic acid were regenerated, then this would be an electron transport developer. Unfortunately, if the other agent is consumed, it is not an ET developer. It is superadditive though.

PE

Say what? I am confused. That's a normal state of mind for me, but I need education. I think the ascorbic acid is consumed and the other agent is not, at least until the ascorbic acid is no longer able to function as a a reducer of the other agent. That seemed to be the conclusion reached by the experiment reported in Mees & James. What sort of concoction would keep both agents from being consumed? Don't give away any secrets if that is what this is about.

It appears that you have said that if either agent is consumed, it is not an ET developer. I don't recall seeking an ET developer. I've gotta go eat. I'll mull it over and try to figure out what you said.

Photo Engineer · Jun 18, 2007

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. Both types can be ET, but the former, with total cycling is distinctive enough to be clearly an ET developer. The latter requires many tests to show if it is an ET developer. It may or may not be. It may just be ordinary superadditivity.

The clue in this in the latter case is if either agent is virtually inactive alone even at high concentrations. Placing a large amount of the most inactive into the developer, and a tiny amount of the other (which is recycled) will give a very active, long lived developer with high capacity. The one at high concentration and with low activity is being used up to regenerate the small amount of the other agent.

PE

gainer · Jun 18, 2007

Photo Engineer said:
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. Both types can be ET, but the former, with total cycling is distinctive enough to be clearly an ET developer. The latter requires many tests to show if it is an ET developer. It may or may not be. It may just be ordinary superadditivity.

The clue in this in the latter case is if either agent is virtually inactive alone even at high concentrations. Placing a large amount of the most inactive into the developer, and a tiny amount of the other (which is recycled) will give a very active, long lived developer with high capacity. The one at high concentration and with low activity is being used up to regenerate the small amount of the other agent.

PE

Now I feel better. That is what I thought I was doing, although I agree that 0.05 moles of p-aminophenol is probably not a relatively small amount for a working solution considering that Rodinal has less than 1/5 that much in a 1+50 working solution. The pH of Rodinal is quite high, while my experimental stuff is between 9 and 10, probably that of a borax solution.

The working solution I use with the concentrate diluted 1+1+25 has only about 0.8 grams/liter.

I should test to see how little I can use.

gainer · Jun 18, 2007

Another factor is that if the developer contains only sodium ascorbate at the pH of borax, we will wait all day for something to happen.

gainer · Jun 19, 2007

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

gainer · Jun 24, 2007

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:

p-aminophenol(base).....1.1 grams
ascorbic acid................8.8 grams
2.4 grams sodium hydroxide + 10 grams borax
or
sodium metaborate........16.7 grams

Water to 1 liter.

FP4+ for 8 minutes at 70 F will still be sufficient for most purposes.

gainer · Jun 24, 2007

I forgot to say that the above recipe is for the working strength solution.

gainer · Jun 27, 2007

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.

gainer · Jul 1, 2007

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.

Experiments with Metol and ascorbic acid.

Privacy & Transparency

Privacy & Transparency