From: Judy Seigel (jseigel@panix.com)
Date: 05/09/01-08:39:52 PM Z
>
> What process(es) are you using it for? In some cases, other dichromates
> may be preferable. Sodium dichromate is less soluble than some other
> commonly used dichromates.
Actually not... it's many times *more* soluble than the other dichromates
we use. In fact for an article in P-F #6 (justjustjust gone to printer,
tadah!) I tried to FIND the solubility of sodium dichromate & after 3
different answers in 3 different books, figured I didn't really really
NEED to know -- but the lowest answer was 75% soluble at 68 degrees, and
it went up to 150%.... another seemed to suggest it was INFINITELY soluble
(as aren't we all).
But seriously folks... saturated solution of potass di is about 10%,
ammonium di about 30% and sodium di.... a lot more. The reason for wanting
*solution* may be because the sodium (ion?) attracts moisture so it's
believed not to keep well, but this is another red herring, because very
easy to put into solution once you get it whereupon it keeps as well as
any of us...
There should be a bunch on this in the archive, because we've done it &
done it.
As for WHY --- IME GUM printing works better with less saturation, but for
the purposes of speculation... maybe the fella wants to try projection
exposure... ???
As to where to get it... Artcraft Chemicals in Schenectady has it, that's
practically in Canada, maybe you can walk over & pick it up... $16/pound.
cheerio,
Judy
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