Sandy King (sanking@hubcap.clemson.edu)
Wed, 13 Jan 1999 19:08:30 -0400
FotoDave wrote:
>I had a suspicion (spelling?) why my dichromate precipitated out but wasn't
>sure. Now the above is giving me some clue. Did you mix your dichromate to
>about 3% strength and dilute as needed?
Dave,
There seem to be few carbon printers around so I post these details at the
risk of boring many on the list. However, here goes . . .
My working procedures for sensitizing carbon tissue are as follow.
1. I keep on hand working solutions in quart bottles of all the strength
solutions of potassium bichromate likely to be needed, ranging from 1/4% to
6%, as determined by the contrast of the negative to be printed. I mix the
working solutions with tap water, but always check this water for pH before
use. With quart bottles I can sensitize tissue up to 12X20", using deep
flat bottom containers.
2. I also keep on hand bottles of fresh stock solution, mixed with
distilled water and stored in glass bottles at room temperature, in the
dark.
3. After a sensitizing session I replenish the working solution with stock
solution of the same strength, adding to the working solution enough to
replace that which was lost.
4. The working solutions is then filtered back into its original bottle and
returned to the refrigerator for storage (at around 40-45F) until the next
use.
(I use coffee filter for this.)
5. To begin a sensitizing session I pour the cold sensitizer into a tray
and allow it to warm up to about 60F for use, which only takes a few
minutes.
Follwing these procedures I have not found it necessry to ever replace in
totu the working solutions. The replenishment procedure replaces the
solutions over a period of time and printing characeristics change very
little, if any, over time.
Hope this is of interest to someone.
Sandy King
This archive was generated by hypermail 2.0b3 on Sat Nov 06 1999 - 10:06:41