Pyrocat HD Question

Sandy Kings formula for Pyrocat-HD calls for the use of Pyrocatechin.

Can Catechol or Pyrogallic Acid be substituted instead?

Thanks,

Don,

I believe Catechol is another name for Pyrocatechin.

I don't know about substititing Pyrogallic acid and what would be gained by this.

"substititing".....what was I thinking of? Of course substituting.

Sandy King used pyrocatechin (aka catechol, pyrocatechol, systematic name 1,2-benzenediol) instead of pyrogallol (pyrogallic acid) as it oxidises much less readily, and Pyrocat HD was formulated for use in rotary processors, where the vigorous agitation leads to heavy oxidation of developer.

I have not come across formulae for any pyrogallol/phenidone developers, though there are a number of pyrogallol/metol developers (the phenidone in pyrocat HD can be replaced with 2.5g of metol). A number of pyro recipes are given on this page.

What is the pH of Pyrocat HD?

Philippe Grunchec said:

What is the pH of Pyrocat HD?

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That I do not know, and I cannot remember having seen it reported anywhere. Though a saturated solution of potassium carbonate has a pH of 11.6.

Reference to Pot. Carb. pH; see section 9. Physical and Chemical Properties.

Catechol, pyrogallol and hydroquinone each have different stain colors. There is no reason why one could not use phenidone with any of them. The pyrogallol has three OH groups. I have made a pyro variant of Pyrocat PC, which used 2/3 the amount of Pyro as of catechol and uses p-aminophenol base instead of Metol. A small amount of ascorbic acid takes the place of sulfite and allows a glycol solvent for the A solution, as all three constituents are soluble in propylene glycol with no special treatment. If you try it, be sure to get the p-aminophenol base, not the hydrochloride. Phenidone is also directly soluble in glycol. You pays your monet and you takes your choice.

Well, it was either the French artist or coin of the realm. I guess you could buy a lot of developer for a Monet.

Trevor Crone said:

Don,

I believe Catechol is another name for Pyrocatechin.

I don't know about substititing Pyrogallic acid and what would be gained by this.

"substititing".....what was I thinking of? Of course substituting.

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One of the things that will happen if you substitute Pyrogallol for Catechol is that the image stain color will change.

Another change will be in the developer activity.

You will also see an image stain color change and developer activity change if you substitute Hydroquinone for the Catechol.

I've certainly noticed a much heavier stain with my normal brew - PMK pyro over Pyrocat-HD. Especially with continuous agitation because of increased oxidation.

Are there any formulas published of pyro + phenidone developers? The only developers I know containing phenidone are Sandy King's Pyrocat-HD (which I do use on occasion) and a few Ilford developers combined with hydoquinone.

Thanks,
Trevor.

Ilford ID-4 was a Metol Pyrogallol staining developer, it's remarkably similar to Pyrocat M, and a Phenidone variant was published in an Ilford Patent - substituting 0.4g Phenidone for the 4g Metol.

The only real difference between Pyrocat and ID-4 is the Ilford developer uses significantly more Pyrogallol (!)x) in the working solution, and consequently has far shorter development times. So you could try substitution but you'd need to experiment

ID-4 or Patent Dev at 1:1 contains
Sodium Metabisulfite . . . . . . . 6 g
Pyrogallol . . . . . . . . . . . . . . 6 g
Metol (ID-4) . . . . . . . . . . . . 2 g or
Phenidone (Patent Dev) . . . . 0.2 g
Potassium Carbonate . . . . . . 37.5 g
Water to . . . . . . . . . . . . . . 1 litre


Pyrocat HD at 2:1:100
Sodium Metabisulfite . . . . . . . 1 g
Pyrocatechin . . . . . . . . . . . 0.5 g
Phenidone . . . . . . . . . . . . . . 0.2 g
Potassium Bromide . . . . . . . . 0.1 g
Potassium Carbonate . . . . . . 37.5 g
Water to . . . . . . . . . . . . . . 1 litre

These are different developers, but by adjusting the level of Pyrogallol it should easily be possible to come up with a developer with some similarities to Pyrocat HD or M.

Ian

I wasn't answering your question as I typed Trevor, but I have

Ian

Ian, thanks for the info on Ilford's ID-4 developer. At 1:1 WS, this is certainly a concentrated developer with regard to the pyrogallol used.

Sorry Don, I'm not trying to steal the thread just interested in the various possiblities.

ID-4 is described as "An energetic staining developer"

By the time Phenidone went into commercial production around 1952 the demand for Pyro developers had declined very rapidly, and Ilford's later research was into using it in other ways. Phenidone & Glycin = Ilfosol.

Ian

The stain of Pyrocat is usually less visible to the eye than that of pyrogallol. We should hear from Sandy King about this subject. For his favored print making, the density of most concern is in the UV. You can have a visually contrasty negative that might be just right for, say, platinum, but with the proper stain color, you can have a negative that can be printed easily on either platinum or VC paper, I believe.

If you were to use catechol in place of hydroquinone in most MQ or PQ developers, you would not notice much if any difference. It takes a lot less sulfite to get rid of the stain of catechol than of pyrogallol. A few days ago, I wanted to make some DK50 but was out of hydroquinone. I used catechol and it worked just fine. I have been told that at one time HC110 used catechol.

Trevor Crone said:

I've certainly noticed a much heavier stain with my normal brew - PMK pyro over Pyrocat-HD. Especially with continuous agitation because of increased oxidation.

Are there any formulas published of pyro + phenidone developers? The only developers I know containing phenidone are Sandy King's Pyrocat-HD (which I do use on occasion) and a few Ilford developers combined with hydoquinone.

Thanks,
Trevor.

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Trevor, was the much heavier stain image stain or general stain?
Was the stain degree determined via visual interpretation or via Blue Channel or UV Channel Transmission Densitometry?

Stain visual appearance can be very deceiving.

Tom,

General stain, very noticable in the rebate of the film, 4x5 HP5+. Visual interpretation. What was pronounced visually was the increase in general stain with this film when processed by continuous agitation.

When I get the time I want to print and compare negatives in Pt/Pd that have been processed in pyro, pyrocat-HD and in a developer such as Ilfosol 3. To date I've only been able to print in Pt/Pd a couple of pyro negatives and Polaroid 55 negatives. The pyro developed negs. needed 4 times the exposure time under UV light (BLB). Visually the pyro negs looked thinner then the Polaroid ones. Just goes to show how much the stain blocks UV light.

Trevor.