U of S | Mailing List Archive | alt-photo-process-l | Re: Do dichromates change with age?

Re: Do dichromates change with age?


The page above says: "...Shelf Life:  Unlimited in tightly closed

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...


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 yazmı�:
>>> 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