PMT, bleach & redevelop
I would like to remind the forum of the virtues of bleaching a negative and redeveloping in a pyrogallol or catechol staining developer. This process can serve for intensification of weak negs and for increasing contrast of negatives for use in some alternate printing processes that require high contrast negatives without destroying their usefulness for ordinary printing on VC paper.
A good developer stock for this purpose is the following:
250 ml Triethanolamine
10 grams pyrogallol
1 gram metol
Heat till it dissolves. About as hot as a cup of tea or coffee will do. The stock keeps very well. Dilute it 1+25 for use either as the original developer or for redeveloping a bleached negative.
For bleaching, use a ferricyanide-bromide bleach such as is used in the sulfide sepia toning process.
Comments from previous article system:
By Ryuji - 12:57 PM, 01-18-2005 Edit Rating: None
PMT is perhaps a confusing name, as it's a common acronym for 1-phenyl-5-mercaptotetrazole, a famous antifoggant used in paper emulsions as well as some accutance developers.
By Ian Grant - 09:04 PM, 03-21-2005 Edit Rating: None
Well although a print toner you could look at Ilford's IT-8 toner. This has additional advantages as it use a dichromate bleach, which is itself used in intensifiers and then a Pyrocatechin redeveloper.
While I've never thought about using it on negatives it definately intensifies prints.
By GeorgesGiralt - 01:58 PM, 02-21-2006 Edit Rating: None
I used PMK to re-devellop a weak negative bleached with the bleach found in Kodak Sepia Toner. I gained some more density making the negs printables. (they were badly exposed and badly dev.) You do not gain anything in silver dnesity as the fixer has already removed all non metallic grains, but the stains adds density and you can repeat the process, if needed.
Good call Sean. The acronym PMT is taken since 1920s in the field of photographic chemistry. I don't recommend the use of PMT for anything other than 1-phenyl-5-mercaptotetrazole.
Let's just call it Pyro-Metol-TEA for long.