Catechol and Superadditivity

[mrred]

I am trying to find optimum ratios for Metol And Phenidone when mixed with catechol, but there doesn't seem to be much reference out there. Much of the recipes out there seem to be using arbitrary amounts. Is catechol close enough to hydroquineone to use the same ratios?

 

[Gerald C Koch]

An interesting question for which there is no easy answer. Catechol is different from hydroquinone in that when used alone it can produce a negative with normal contrast. Hydroquinone cannot do this. During the 1930's and 1940's catechol developers were popular in Europe particularly in Germany. They used only catechol as the developing agent and sodium hydroxide a the accelerant.

The use of catechol fell out of favor afterwards probably because it was more expensive than hydroquinone and offered no real advantage to a MQ or PQ formulation. This probably is responsible for the paucity of information on catechol. I would suggest an empirical approach starting from the usually recommended Metol and Phenidone ratios for hydroquinone based developers.

As far as optimal ratios for developing agents are concerned they are not really used that much. The optimal Phenidone to hydroquine ratio as say given by Mason 1:26 is seldom seen. What is seen are ratios 1:40 or even higher. This is partly explained by the higher cost of Phenidone. The optimal ratio principally effects the speed of development rather than the final result. Mason has a graph showing the results of development speed to the PQ ratio. It is a U-shaped curve so speed of development slows as the ratio changes from the optimal ratio. The optimal ratio for Metol to hydroquinone is 1:6.

Of all the "experimental" developers containing Phenidone on APUG particularly the pyro ones I would speculate that optimal ratio was never a consideration in their formulations.

 

[mrred]

The reason I am doing some tests is from my experiances with PyrcatHD/MC and Hypercat. I find the Hypercat strait forward and gets good results with a vary simple formula. I find the Pyrocat family with a more complex formula with no real benefit over the Hypercat.

My tests were with three different batches of hypercat; one unchanged, one with 1g of metol and the other with 1g of phenidone all based on ratios used in Pyrocat/x. The Metol batch was more active and developed significantly more stain. The Phenidone batch was extremely active but only produced as much stain as the unchanged hypercat.

The metol has no real change in sharpness over the catechol only and the phenidone is noticeably sharper. Because of the no change in stain in the phenidone version, I suspect it is not balanced at all. But I'm just guessing.

Based on what I have seen with standard ascorbic acid or hydroquineone developers, phenidone is used in much lower quantities than metol. I just have nothing to go on with the catechol. I guess it's time to burn through the stuff.

Hypercat only....



Hypercat + Metol



Hypercat + Phenidone



The last example was significantly over developed because of a more than predicted activity increase.

 

[mrred]

I took a stab today after seeing a reference on the UnblinkEye by Mr. Gainer. He refereed that 4:1 was his magic ratio. I chose 5:1 for convenience.

Part A

70 ml dist water
7g sodium bisulfite
5g catechol
1g metol
top to 100ml dist water

Part B

70 ml dist water
0,5g potasium bromide
10g sodium hydroxide
top to 100ml dist water

The activity is remarkably greater that Hypercat which uses 20g catechol with the same volume. It is slightly more active than Pyrocat-MC. It produces about the same stain. There doesn't seem to be any real change in IQ, but my eyes are the only tools here.

My next batch will be to reduce the amount of sodium bisulfite with the hopes of increasing the stain.

 

[Gerald C Koch]

Despite the injunction De mortuis nil nisi bonum Mr Gainer's knowledge of photochemistry was rather limited. I would start with the ratio of 1 part Metol to 6 parts of catechol as recommended by Mason. That should also improve the amount of stain produced.

 

[mrred]

Just a place to start. The results look promising. I am not that far off now, might just add a bit of catechol to the existing mixture.

I was right about the bisulfite. The strip hanging now has slightly more stain than the previous one.

I find it strange that when I mix my A & B, it becomes blue. Hypercat or Pyrocat never did that for me. Any explanations why?

 

[Gerald C Koch]

Is it a deep blue like blue ink?

 

[mrred]

Yes, but only when A and B meet. Develops as expected.

 

[Gerald C Koch]

Simple organic compounds are usually colorless or yellow in color. An intense color often indicates that a free radical is being formed. Some years ago I did the synthesis of the developing agent pyridylhydroquinone as given in a citation in Glafkides. The chemical crystallized out as yellow needles. When I used it to make a developing solution the solution turned dark wine red when sodium carbonate was added. The resulting solution did act as a developer.

 

[Wayne]

I hadn't heard that Pat died, only that he is not very well...

 

[mrred]

I guess I have an entertaining developer. I bumped the ratio up to 6:1 and the results look good, good enough to use. This did suck up the last of my chatechol so I guess I need to focus on using than tinkering.....until the next order is done.

 

[mrred]

For the record, the final version I am using is

Part A

70 ml dist water
3.5g sodium bisulfite
6g catechol
1g metol
top to 100ml dist water

 

[Alan Johnson]

I took a stab today after seeing a reference on the UnblinkEye by Mr. Gainer. He refereed that 4:1 was his magic ratio. I chose 5:1 for convenience.

Part A

70 ml dist water
7g sodium bisulfite
5g catechol
1g metol
top to 100ml dist water

Part B

70 ml dist water
0,5g potasium bromide
10g sodium hydroxide
top to 100ml dist water

The activity is remarkably greater that Hypercat which uses 20g catechol with the same volume. It is slightly more active than Pyrocat-MC. It produces about the same stain. There doesn't seem to be any real change in IQ, but my eyes are the only tools here.

My next batch will be to reduce the amount of sodium bisulfite with the hopes of increasing the stain.

At hypercatacutancedeveloper blogspot catechol is 10g/100ml PG and he uses 20g/100ml sodium carbonate.
Likely your sodium hydroxide gave a higher pH and that increased activity.

 

[juan]

FYI, Pyrocat PC turns bright purple when A and B are mixed.
Juan

 

[LarsAC]

Pyrocat MC as well.

Lars

 

[mrred]

At hypercatacutancedeveloper blogspot catechol is 10g/100ml PG and he uses 20g/100ml sodium carbonate.
Likely your sodium hydroxide gave a higher pH and that increased activity.

I never used the sodium carbonate alkali. I always used the alkali described here. The comparisons are valid. At the end of the day, properly develop negs in any of these developers will look the same or close enough not to be able to tell the difference.

Said that, the point here was not so much to make a better developer. It was to more efficiently use the "expensive for me to get" catechol, which it does. I didn't use phenidone because I have 5 lbs of Metol. It's not re-inventing the wheel here, just more with less.

 

[mrred]

A bit of an update........ I've been having issues with metol breaking down without sodium sulfite in the mix. Sometimes a couple weeks were all I got.

Looking at Pyrocat-HD site I tried going back to glycol and using ascorbic acid to scavenge, but it still broke down. I tried their suggestion with glycerine and essentially the same results. My latest stab with tea / water trick works much better as I am working with a sample for three weeks and and it has only turned slightly orange.

Suggestions or explanations are welcome.

 

[Alan Johnson]

Aminophenols give colors on oxidation:
http://www.sciencemadness.org/talk/viewthread.php?tid=14372
Oxidation is slower if acid is used to lower the pH.

 

[juan]

Pyrocat PC turns purple. I guess this explains it.
Juan

 

[ritternathan]

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.

These are the instructions that I followed and have used to make Pyrocat-MC at home. You can use the TEA and/or water method but it mostly defeats the purpose of using glycol in the first place. I used an old candy thermometer. Use pyrex and thick, good heat resistant gloves and do it outside if you can.

 

[RalphLambrecht]

I am trying to find optimum ratios for Metol And Phenidone when mixed with catechol, but there doesn't seem to be much reference out there. Much of the recipes out there seem to be using arbitrary amounts. Is catechol close enough to hydroquineone to use the same ratios?

I've decided long ago to leave developer development to the few who know what they are doing.ehen ever I mess with an existing formula, I mess it up and have to go back with my tail between my legs.

 

[Alan Johnson]

I find it strange that when I mix my A & B, it becomes blue. Hypercat or Pyrocat never did that for me. Any explanations why?

It's probably a blue oxidation product of metol (N-methyl aminophenol). Mixing Perceptol, which is metol based with hydrogen peroxide also gives a blue color.

 

[Gerald C Koch]

It is seldom necessary to use more than two developing agents in the same formula. Occasionally you will see a third one like Glycin or PPD but their presence is for other purposes. Both Metol and Phenidone are super-additive with catechol so you could eliminate either one. As mentioned in my previous post, the optimal ratio effects only the rate of development but NOT is final outcome. So it is more of a theoretical consideration than a practical one. You will find ratios for the same developing agents that vary widely. Usually the bottom line is the determining factor.

 

[Rudeofus]

A bit of an update........ I've been having issues with metol breaking down without sodium sulfite in the mix. Sometimes a couple weeks were all I got.

Assuming you refer to part A as listed in (there was a url link here which no longer exists), there is some form of Sulfite in your mix, it's just not very much.

I have two questions:

1. For some reason I don't know a single Metol based developer which is sold as a concentrate, which strikes me as odd. Does anybody here know one, even it it contains a secondary development agent or is/was sold as two part concentrate ?
2. Your part A concentrate is not that much different from D-23 working solution with an extra 60 g/l Catechol and, of course, an acidic pH. Both the Catechol and the low pH should IMHO extend working solution shelf life of D-23, so your concentrate should last longer that the 6 months specified for D-23. Are you sure that your part A is toast after a few weeks, or does it just change color?

 

[mrred]

Aminophenols give colors on oxidation:
http://www.sciencemadness.org/talk/viewthread.php?tid=14372
Oxidation is slower if acid is used to lower the pH.

I tried ph -5 to -10, same results. Infact, my first instinct was to lower the ph.