Oriu a écrit :... Les papiers multigrades semblent assez fragiles tout de même
Pour "confirmer" ce que tu dis Oriu, quelques infos trouvées sur l'Internet à propos du vieillissement du papier:
"Also it depends upon the presence of developing agents in the paper. I recall that Kodak Polycontrast paper incorporated developing agents in the paper which speeded up tray processing and even made Ektamatic processing possible (although Kodak didn't specifically recommend it.) I believe the last Agfa RC papers had developing agents and some Ilford papers have them. I think these papers might be more prone to fogging."
"If you still have Ilford MG III you can dump it. MG IV will be OK till 10-12 years, depending how the storage is/was. Old Agfa paper in MG like the MCP and MCC (made till end 2005) you can dump in the mean time too. Old Agfa papers and OrWo (fiber) papers (before 1994) without incorporated developer (e.g. Portriga) can be still reasonable good.
Old Kodak papers (before 2004) like Polycontrast you can dump in the mean time too.
Foma: Fomaspeed Variant III, about 8-10 years. The same about Fomabrom Variant. Fomatone MG papers a little bit longer beacuse these Chlorosilver papers have a very slow speed (4 times less then above mentioned Foma MG papers).
About Forte: Ended since 2007. I have one package PW14 MG left in 50x60cm/10 sheet so we will see what is left from this paper.
Kentmere, overtaken in 2007 by Ilford and in the mean time a 100% Ilford/Harman production. So not so different then MG IV now.
Amaloco Variprof: See MG IV. They ended the supply around 2006. The same about Tetenal.
Rollei papers: See Foma, 100% compatible.
Bergger, made by Ilford too since 2008 (before 2007 by Forte). Made on special application but I do not use them so much so I can not give any input about storage time."
Un autre truc intéressant peut-être:
"Benzotriazole is used as an organic antifoggant and density depressant in developers.
Benzotriazole acts as a restrainer without affecting other properties of the developer. It can also be used as a fog restrainer when processing out dated papers
When blue-black or cold-black image tones are desired with bromide papers, benzotriazole should be used in addition to, or substituted for, potassium bromide
Make a 0.2% solution of benzotriazole (2 grams benzotriazole in water at 125°f/52°c or higher to make 1 liter) then reduce the bromide to 1/10 or 1/6 strength and use just enough Benzotriazole solution to prevent developer stain or fog. A little experimentation may be required.
The same treatment can be applied to chloride and chlorobromide papers to eliminate any greenish black tendencies and/or achieve a blue-black tone."
Je crois me souvenir que le révélo Ilford Multigrade contient du Benzotriazole. D'où, sans doute, des blancs plutôt froids que j'ai constatés, et dans le cadre de mon souci, une réduction de l'effet de voile en bordure de mon papier...
Il semblerait que je puisse remplacer partiellement ou en totalité le Bromure de Potassium dans mon D72 par du Benzotriazole
Je vais essayer d'en trouver pour test...
Juste pour dire...
