Re: Do dichromates change with age?
http://www.hummelcroton.com/msds/amdic_m.html The page above says: "...Shelf Life: Unlimited in tightly closed container..." What I understand from this (and the previous page) is that heat + humidity is definitely a factor affecting shelf life of dichromates. Contamination also is an important concern. I purchased my Ammonium Dichromate 5 years ago and it acts the same. (Yes, I know that's nothing close to 20 years!) I remember reading someone (British?) using NH4Di (maybe it was KDi) as old as 30 - 40 years in the list archives but I'm not sure... Regards, Loris. 14 Temmuz 2008, Pazartesi, 5:01 pm tarihinde, sam wang yazmış: > Hi Loris, > > The bulb is quite new, and I haven't noticed any speed loss with > palladium. The integrator on the Amergraph reads UV, so that's the > reason I replaced my old NUARC with it (integrator in the NUARC reads > visible light). > > There are many other possible answers. Just wondering if dichromates > could lose potency. > > Sam > > On Jul 14, 2008, at 9:44 AM, Loris Medici wrote: > >> 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 yazmıÅ�: >>> 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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