Catechol-Metol : LUSENET : B&W Photo - Film & Processing : One Thread

I'm experimenting with a Catechol-Metol film developer and trying to find the right times for APX 100 and Efke films. The recipe is from the 30's and the results so far seems good. This is the recipe:

Warm water 750 ml Metol 9g Catechol 9g Sod. Sulfite 60g Sod. Carbonate 60g Cold water to 1000 ml

Dilute 1+9 or 1+19.

Does anyone know how the catechol and metol work together?

-- Patric (, August 03, 2001


Much like hydroquinone and metol. the only diference is that catechol is a tanning developer. Catechol formula is o-dihydroxybenzene and hydroquinone is p-dihydroxybenzene, as you can see the only diference is in the placement of the hydroxyl group, this might be significant in the superadditivity effect, but I suspect it is not. Without doing a complete mechanism study is hard to tell but it is my feeling that metol/catechol and metol/hydroquinone behave very similarly. It is one of the reasons I dont use metol in my formula, I think your stain will improve if you reduce the metol quantity, plus you will get a better "compensation" effect from the stain with less metol. The only draw back to reducing metol is the smaller EI. Ok, good luck with your formula.

-- Jorge Gasteazoro (, August 03, 2001.

Jorge is right on with his comments. The ratio of metol to catechol is too high to benefit from the unique qualities of catechol, even though catechol and metol are mildly superadditive. My guess is this formula stains very little, if at all. This is because metol is doing most of the work and the catechol is not oxidizing enough to provide the staining byproducts of oxidation. In part this is due to the ratio, but also because the alkaline component (carbonate) is not high enough to sufficiently activate catechol in this formula. If you reduced the metol to 1 or 2g, and extended your developing times roughly 50%, you would begin to see the potential of these components.

A more modern and well regarded formula is Pyrocat-HD. It uses 5g cat, 1g metol, 2g sodium bisulfite / 100ml distilled water; this is combined with a 100% solution of potassium carbonate (100g/100ml H20), mixed at 1:1:100 with water. Development times are between 10 and 13 minutes. There is an alternative formula for Pyrocat-HD which calls for phenidone in place of metol. You can find the details at

-- Ted Kaufman (, August 03, 2001.

Thanks! You're right, I got no stains on the negs. The good things though is the very fine grain and better result with APX 100 than with D-76. I've always got strange mid-tones with D-76 and this film.

The Pyrocat HD developer seems interesting. I will try it when I buy Potassium carbonate later this fall.

Here is another Catechol/Brenzkatekin developer I will try, Mimosa No. 3:

A Sodium Sulphite 30 g Pyrocatechin 20 g Potassium Bromide 0,5 g

B Sodium Carbonate 120 g

For use, mix 1 part of I and 1 part of II with 10 parts of water.

I wonder though if the Bromide will affect the staining? Any thoughts?

-- Patric (, August 04, 2001.

Ok, I will make this easier for you. The potassium bromide is there as an antiffoging agent, I have never seen fogging with my formula and I don't use potassium bromide or any other antiffoging agent. as a matter of fact with Tmax 100 my b+f is 0.03. In any case if you want to add it it wont dimish your stain. The sodium carbonate (Na2CO3) is there to activate the catechol by increasing the pH as it will decompose into sodium hydroxide. You might as well save yourself some money and add about 5 to 8 grams of sodium hydroxide instead of 120 grams of sodium carbonate!

-- Jorge Gasteazoro (, August 04, 2001.

Thanks. I've seen Sodium Hydroxide being sold as "Caustic Soda" at the stores. I will check the purity before I buy. Buying from a pharmacy will be more expensive.

-- Patric (, August 04, 2001.

Patric, Sodium hydroxide and caustic soda are the same thing, with the same purity. The thing you have too look for is wether it is technical grade, analytical grade etc. For our purposes technical grade is good enough.

-- Jorge Gasteazoro (, August 04, 2001.

That's what I meant, Jorge. I will call the company that makes the household chemicals and hear what grade it is. Probably technical grade, but is it 85% or 99% Sodium Hydroxide? Good to know before mixing the developers.

-- Patric (, August 05, 2001.

I dont get it, are you buying a solution or are you buying the pellets? (solid) if you are trying to buy a solution dont waste your time, go and buy the solid sodium hydroxide. In a pharmacy they will try to sell you a solution of sodium hydroxide that only costs $0.30 to make for $5.00. I dont know where you live but photgraphers formulary and Bostic & Sullivan ship all over the world, check theit web site and get it form them, not a pharmacy.

-- Jorge Gasteazoro (, August 05, 2001.

I live in Sweden. The household Sodium Hydroxide comes as pellets. Are you saying that the hydroxide in pellet form are 100%? Maybe I'm a little confused since the sulfite and carbonate somes in crystal, monohydrated and anhydrous form. The pharmacy sell 1 kg, 1000g, sodium hydroxide for $30.

-- Patric (, August 05, 2001.

You got it! if you buy the peellets that is 100% sodium hydroxide, you cand then do the solutions as you want, and/or just weight 5 to 6 grams and add it to your developer. No need to buy a solution and then figure out how much NaOH is in the solution etc. BUY THE PELLETS, 100% NaOH.

-- Jorge Gasteazoro (, August 05, 2001.

Ah, I forgot, when you disolve the pellets you will generate heat, so be careful! Yes the other compounds you mention come in many different hydrated forms and also in anhydrous form, but not the sodium hydroxide. Now sodiu hydroxide is hygroscopic, so it will pick up moisture from the atmosfere if you leave the jar open too long, so open it, weight what you need and then close it again, and you should have enough to last you for many, many gallons of developer.

-- Jorge Gasteazoro (, August 05, 2001.

Thanks again! I called the chemical company and the chemist there said that the pellets are close to 100% hydroxide, but that they use a very small amount of salt when they make the pellets.

-- Patric (, August 06, 2001.

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