Re: Do dichromates change with age?
My dichromates, even mixed with water, were fine 6 yr old...and I, too, have read, as below, that they do not go "bad" with age in a number of places, so in limited theory and practice I don't think it is your dichromate. Gumming away, eh, Sam? What are you working on? Speaking of (as you were a few posts ago) going through all your negatives, I just received 3000 glass slides and 8000 cardboard mount slides as well as a bunch of negatives from the 20's and 30's---maybe 15,000 images in all. So I have my work cut out for me, distributing to different historical places. I'm quite concerned because the slides are molding. BW negatives look good, though! Makes me realize that before I die, my photographs better be in order or else. I've gone through 70 of the 100 carousels and had to mercilessly toss. Chris ----- Original Message ----- From: "Loris Medici" <mail@loris.medici.name> To: <alt-photo-process-l@usask.ca> Sent: Monday, July 14, 2008 8:50 AM Subject: Re: Do dichromates change with age? http://www.colourchromes.com/potassium_dichromate.htm This page says: "...It is non-caking and if stored in a cool, dry place away from heat, shelf life is indefinite..." Another thing to consider would be contamination... Regards, Loris. 14 Temmuz 2008, Pazartesi, 4:44 pm tarihinde, Loris Medici yazmış: Hello Sam, A question: does your unit have a light integrator? If yes, by saying "longer exposure time" you mean "more units" right? If not (more units), then could it be that your lightsource is getting weaker somehow (either due bulb wear and/or voltage fluctuations)... Have you absolutely ruled out probable problems about electricity / integrator / bulb ect.? Regards, Loris. 14 Temmuz 2008, Pazartesi, 4:30 pm tarihinde, sam wang yazmış:Has anyone come across any data about whether dichromates losing speed, or effectiveness? My jar of ammonium dichromate is probably over 20 years old (yeah, I use very small quantity in gum printing) and it appears to suddenly need longer exposure time. Doesn't make sense, especially since I'm using an Amergraph printer for exposure. Humidity and everything else has been kept fairly consistent. Anyone else has similar experience? Sam
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