Pyrocat: Versions and Mixing Directions

[sanking]

Pyrocat – Versions and Mixing Directions

I am attaching mixing directions for various versions of Pyrocat, including –HD, -M, -P, -MC and -PC. I am indebted to Pat Gainer for his advice and recommendations for mixing the glycol based versions of Pyrocat, including Pyrocat-HD, -MC, and -PC.

Pyrocat-HD is the original Pyrocat formula and is still the most popular judging by sales and questions I get about it. The other formulas, which include Pyrocat-M and Pyrocat-MC, and Pyrocat-P and Pyrocat-PC are recommended primarily for rotary processing, where they tend to give slightly greater acutance than Pyrocat-HD.

All of the Pyrocat formulas are acutance developers that give good pictorial rendition when used at dilutions of 1:1:100 to 2:2:100 with normal agitation. When used at higher dilutions with reduced agitation they become high acutance developers with very pronounced adjacency effects. Pyrocat can also be used as a two bath developer. See instructions at end of this message.

Some of the characteristics of all of the Pyrocat variants are:
1. Good acutance.
2. Tight grain pattern with some grain masking from stain.
3. Lower levels of general stain, even with long development times, than most pyrogallol based developers.
4. Does not cause uneven staining or streaking when developed in Jobo.
5. Can be used with dilute solutions and minimal agitation for very pronounced adjacency effects and enhanced apparent sharpness.
6. Very inexpensive to use.
7. Stock solutions last a long time. A year or slightly more when mixed in water, and up to several years when Solution A is mixed in glycol.

All of the Pyrocat versions use the same Solution B, which is a 75% solution of potassium carbonate. It is possible to substitute a 20% solution of sodium carbonate but if you do so the working formula must be mixed at 5X the amount of Solution B. Thus, a dilution of One Part A + One Part B + 100 Parts water when using the 75% potassium carbonate solution would become One Part A + Five Parts B + 100 Parts water.


A. Pyrocat-HD (For one liter of Stock Solutions A and B)
Part A
Distilled Water (50° C) 750 ml
Sodium Metabisulfite 10 g
Pyrocatechin 50 g
Phenidone 2.0 g
Potassium Bromide 2.0 g
Distilled Water to make 1000 ml

Part B
Distilled Water 750 ml
Potassium Carbonate 750 g
Distilled Water to make 1000ml

Mixing Directions for Stock B.
1. Start with 700ml of distilled water.
2. Weigh out 750g of potassium carbonate and add the chemical very slowly to the water, with constant and rapid stirring. If you add the solution too fast, or don’t stir enough, it will be impossible to dissolve all of it in the water. As you add the chemical an exothermic reaction takes place and the solution will warm up appreciably.
3. Add distilled water to 1000ml.
Tests show that the Pyrocat-A stock solution is stable in partially full bottles for up to a year. If shelf life of longer than one year is desired I recommend mixing Stock A in glycol. Stock Solution B has indefinite shelf life.
Mixing one-liter of Pyrocat-HD Stock A solution in propylene glycol.

1. Weigh out all of the chemicals for Stock A.
50.0g of pyrocatechin, 10.0g of sodium metabisulfite, 2.0g of Phenidone and 1.0g of potassium bromide.
2. Pre-heat 750ml of propylene glycol to about 150F in a water bath or hot plate stirrer.
3. Add the pyrocatechin to the warm glycol and stir until dissolved. Should take no more than about a minute.
4. Add the phenidone and stir. Should dissolve completely in about a minute.
5. Add the bromide and sodium metabisulfite to about 50-75ml of hot distilled water at about 120F. Stir until completely dissolved, and then add this solution to the propylene glycol solution.
6. Top off the solution with glycol to 1000ml.

Pyrocat-HD Stock Solution A, when mixed in propylene glycol, has a shelf life of several years.

B. Alternative Pyrocat-HDC mixed in glycol.
Pyrocat-HDC

Stock A
Propylene Glycol at 150F 750ml
Pyrocatechin 50 g
Phenidone 2.5g
Ascorbic Acid 4.0g
(Mix in the order noted and stir until dissolved)
Glycol to one liter.

Pyrocat-HDC gives almost identical results as –HD with most films and development methods.

C. Pyrocat-P (Solution A mixed in water)
Stock A
Distilled Water at 120ºF 750ml
Sodium Metabisulfite 10.0g
p-Aminophenol 5.0g
Pyrocatechin 50g

D. Pyrocat-PC (Solution A mixed in glycol)
Stock A
Propylene Glycol at 150F 750ml
Pyrocatechin 50g
p-aminophenol 5.0g
Ascorbic acid 4.0g
(Mix in the order noted and stir until dissolved)
Glycol to one liter.


E. Pyrocat-M
Stock A
Distilled Water at 120º F 750 ml
Metol 2.5g
Sodium Metabisulfite 10g
Pyrocatechin 50g
Water to 1000ml

Notes:

1. Mix the chemicals in the order given and stir until dissolved before adding the next chemical.

2. The use of the potassium bromide restrainer used in Pyrocat-HD is not needed with Pyrocat-P and Pyrocat-M because of the lower pH threshold of metol and p-aminophenol than phenidone.


F. Pyrocat-MC

Stock A
Propylene Glycol at 150F 750ml
Pyrocatechin 50 g
Metol 2.5g
Ascorbic Acid 4.0g


Mixing directions. Start with about 8ml of TEA at room temperature and a spoonful of water. Now add 2.5 g of metol and stir to make slurry. This is eventually going to make a liter but you can start in a 1/4-liter cup. After the slurry gets a little more fluid, add 15-20 ml of some warm propylene glycol. Now you can transfer the metol slurry to the 750ml of warm propylene glycol and stir until dissolved. Now add 50 grams of pyrocatechin and stir until dissolved. Add 4.0g of ascorbic acid and stir until dissolved. Add glycol to one liter.

Alternative mixing directions. Heat the glycol to about 250 F and all of the chemicals will readily go into solution with no water required. Mixed this way the solution will be even longer lived. Add glycol to one liter.


Pyrocat as two-bath developer. Many two-part developers can be used as two-bath developers. Barry Thornton's Diaxactol was originally marketed as a two bath developer, though apparently not a very good one as it was later re-marketed as a single bath developer.

Pyrocat-HD can also be used as a two-bath developer with excellent sharpness. For this I recommend a 1:10 dilution of both Parts A and B, with solution temperatures at 75F.

1. Water bath for three minutes. Not necessary for most films but I recommend the water bath for Fuji Acros, Tmax-100, Delta 100, and most fine grain films of ASA 100 or less.

2. Six minutes in Part A, with two inversions at the beginning, and two inversions at the 1/4, 1/2 and 3/4 points of development.

3. Pour our Solution A and pour in Solution B. No rinse between. Initial agitation two or thee inversions, then two or three inversions at the 1/4, 12 and 3/4 points of development.

4. Pour out B, pour in water and leave for five minutes.

The purpose of the relatively long time in B and the final water bath is to allow developer exhaustion for maximum adjacency effects.

When used this way Pyrocat-HD is a high acutance compensating developer.

Pyrocat-HD negatives with the two-bath method described above have higher acutance than with one bath development and intermittent agitation.

Both Solution A and Solution B can be re-used several times within a three-four hour period but should be discarded at the end of a development session as they will go bad in about 10-12 hours.

[Jim Noel]

Thanks for the update.
Jim

[Lee L]

Sandy,

Thanks very much for taking the time to post this in one place.

Lee

[Jeremy]

Can we make this an article or "sticky" post? Thanks for putting this all in one place, Sandy.

[mikebarger]

It is in the articles section under staining developers

[john_s]

Sandy, there's an error "dichromate" should be Carbonate.

[sanking]

Sandy, there's an error "dichromate" should be Carbonate.

Thanks. I corrected it.

As a carbon transfer printer I have dichromate on the brain.

Sandy

[john_s]

I had never before seen the alternative mixing directions for Pyrocat-MC (without a little water). Is the list of ingredients just those in the list under the heading "Stock A" or should one use some TEA as well?

Could that amount of heat (250degF=120degC) do some damage to any ingredient? I have mixed some formulas at lower temperature than recommended by allowing lots of time for dissolution (a week in the boot/trunk of the car on long trips). Would this be worth a try for this formula?

[sanking]

I had never before seen the alternative mixing directions for Pyrocat-MC (without a little water). Is the list of ingredients just those in the list under the heading "Stock A" or should one use some TEA as well?

Could that amount of heat (250degF=120degC) do some damage to any ingredient? I have mixed some formulas at lower temperature than recommended by allowing lots of time for dissolution (a week in the boot/trunk of the car on long trips). Would this be worth a try for this formula?

This is the first time the alternative method has ever been suggested. Pat Gainer tried it a few days ago and said that it worked, so I decided to recommend it. The high temperature will not damage any of the ingredients so far as I know. I have mixed pyrocatechin, metol and ascorbic acid before at this temperature and there was no problem. You don't need any TEA or water mixing this way.

I suspect that you could mix at a lower temperature with a hot plate stirrer but have not actually done so. Pyrocatechin and ascorbic will definitely go into solution at a much lower temperature, not sure about the metol.

Sandy

[gainer]

I think my report to Sandy was a little garbled or something. My experiment used a 100 ml of glycerol (also callsed glycerin) to hold the Metol and ascorbic acid. Heat it to 250 but no higher than 300 F.This heating drives the water form the hygroscopic glycerol. Now add 4 grams of ascorbic acid, stir it well and add 2.5 grams of metol. The result should be a clear yellow-orange soultion which will remain clear as it cools. Now add 50 grams of catechol and enough propylene glycol to make a liter. Heating helps dissolve the catechol, and it won't hurt to make it hot enough to boil off any water that might be in the glycol. The stock solution becomes considerably redder when the catechol is added.

You may find other uses for the glycerol solution of Metol and ascorbic acid. I made a double batch just so I'd have some to play with. I used the extra to make a water based Pyrocat MC stock just to see how long it would last. I'll tell you a year from now how it faired. Its pH is about 3, which should help it keep a while.

I don't think the glycerol mix is a simple solution. For one thing, only 1 gram of Metol should have remained dissolved on cooling. I have my own ideas about what chemical reactions may be going on between the H2SO4 of the Metol and the glycerol at 250 F but I rely more on pracrice than on theory, especially if there are two or more theoretical explanations.