View Full Version : Hydrocat??

17-Feb-2011, 23:33
Has anyone tried Hydroquinone instead of Pyrocat in the Pyrocat HD [the normal version]. I read at one stage that they could be substituted 1 for 1 as they are from a similar chemical family. I think it was Pat Gainer [APUG] who was suggesting that could be done. I wonder if it would be a similar developer, or if anyone has tried it? I can get the Hydroquinone but not the Catchetol [?]


18-Feb-2011, 00:04
Hydroquinone doesn't act in the same way as Pyrocatechin, it only has very mild tanning /staining properties.

Pyrocatechin on it's own works as a surface developer as in the Windisch compensating formula, because it tans and hardens film proportionally to the amount of exposure & development.

Yes you could substitute Hydroquinone for the Pyrocatechin but you'd get a developer that had very few or little of the beneficial attributes that make Pyrocat such a good developer.

A better substitution would be Pyrogallol but it has a tendency to oxidise faster.

Try looking for Pyrocatechin by it's different names, Pyrocatechol, Catechol, 1,2-dihydroxybenzene it's used outside Photography so should be available from a good chemical suppliers.


18-Feb-2011, 00:51
You are always a great source of knowledge, thanks as always Ian :)

Gem Singer
18-Feb-2011, 07:16

Ilford DDX developer contains Hydroquinone and Phenidone as the reducing agents.

I used DDX for many years and had difficulty controlling development of the highlights.

Switching to Pyrocat-HD solved the problem.

Perhaps the Photographer's Formulary can ship Pyrocat-HD (in Glycol) to Australia.


18-Feb-2011, 13:51
I have tried to replace Catechol with Hydroquinone. With very little sulfite or ascorbic acid produces an intense yellow mask. The problem could not solve was that hydroquinone is a strong developing agent at a pH of more than 10 or 11. Long time to start developing and then makes a breakthrough infection to achieve maximum density of the negative. Produces a large edge effect (high apparent sharpness), but it was uncontrollable for me.
Claudio Sz

18-Feb-2011, 19:42
I tested the "formula" that I had substituted but like Gem and Claudio the highlights were very difficult to control. The rain has stopped so I will return to something that is working correctly. :)

9-Oct-2015, 09:53
Has anyone tried Hydroquinone instead of Pyrocat in the Pyrocat HD [the normal version].

At least one person seems to do it successfully http://www.apug.org/forums/viewpost.php?p=146256

I've just mixed some up to try with x-ray film but I have no experience with staining developers to compare it to.