Aging Dichromate (among other chemicals)

On Thu, 15 Jan 2004, Christina Z. Anderson wrote:
> This idea that dichromate "ages" is in the literature, because when I came
> back to gum after a 5 year hiatus, I was going to throw out my old
> dichromate mix and begin fresh; decided not to, and it was fine. One of the
> myths of gum.

Actually, Chris, you remind me that I generally find chemicals last much
longer than is official, tho I hesitate to say indefinitely. I have about
100 chemicals on the shelf that get used quite rarely (how many can you
use in a day?), and recall only one time that something didn't work, so I
threw it out & got new & the new didn't work either. But for instance
vandyke brown works fine after a couple of years, even when the solution
has gotten black specks & murk. It seems to go right back into solution
when spread.

I suspect the "keeps for 6 months" I've read is just to be on the safe
side, that nobody knows for sure and circumstances alter cases -- that
original condition, fullness of the container, temperature in the storage
space, etc. can have an effect.

Mixed Dektol turns brown but still "works" in my cellar. I suspect though
that where you don't see interim results or do a test strip, as with
developing film, you need your chemicals more precise.

Oh I just remembered one chemical that did go bad in 6 months and that
was in the refrigerator. I was using thiourea dioxide in "Manotone" as a
plating-out toner. After a relatively short time (maybe 2 months) it
still toned but lost the plating effect.

But last week I had to throw out nearly a whole jar of baker's yeast...
a year out of date & failed the yeast test -- would not raise bread....
That's an item (like humidifiers) VERY hard to find in my neighborhood, so
it was regrettable. Thiourea dioxide I can always order from a catalog --
or could, maybe it's on a forbidden list now?

Judy
Received on Thu Jan 15 15:42:13 2004