disposal of dichromate

About this list Date view Thread view Subject view Author view Attachment view

From: Judy Seigel (jseigel@panix.com)
Date: 06/18/03-02:57:45 PM Z


Don't try to dispose of the water, especially if you're printing large.

You can have gallons of water for only a few grams of solid waste.

What I found was that left to settle, the solids sink to the bottom of the
tray -- I'd start a print in the "very dirty" tray & leave it for a few
minutes until most of the dichromate had streamed out. If you're not
overexposing, this happens within a few minutes. Then I'd move the print
to clean water, and continue developing. What comes out now is pigment and
gum, which in my city system, still in relatively small volumes, can be
put into the sewer water.

I found that the dirty tray could go for a long time, but when left to
settle, within a couple of days the top water is quite clear. Decant that
and pour the glop left into a pail or whatever & let it evaporate -- you'd
be surprised how little volume is left, and quite a lot of that will in
fact be gum & paint. A month's work will probably fit in a tuna fish
can -- and can be disposed of in the garden, or a toxic waste site.

I'll add that I use a weak dichromate solution so the volume of dichromate
is less anyway. Using equal parts 10% dichromate for a total of 5 mls of
emulsion which makes a pretty large print is --- how much dichromate?
Hmmm... 100% dichromate would be 5 grams, 10 percent would be, uh, 1/2
gram? ...half of that would be 1/4th gram, less volume of the paint...
Maybe\/probably my logic is off, but clearly it's not a lot...

I'll add BTW that the business about dark effect & having to use the
coated print right away is only true with the modern strong emulsion --
used at saturation. If you read the old books, you'll find printers saying
they stored paper for a month. But then you'll see they used 5%
dichromate, with 2 parts gum to 1 dichromate. And it depends what your
negative is like too. The other day I forgot a coated paper, and found it
about 4 days later. So I exposed less -- 2 minutes instead of 3 or 4 &
then left in water for about 18 hours. It made a perfect print --
although granted it was a high contrast negative.

Judy


About this list Date view Thread view Subject view Author view Attachment view

This archive was generated by hypermail 2.1.5 : 07/09/03-08:31:13 AM Z CST