[alt-photo] Re: Gum washing?

[Christina Anderson]

Johnny,
I wash 20 minutes when I clear stain. But since I began to use the lesser strength ammonium dichromate (10-15%, not saturated) I don't have problems with dichromate stain anymore and have not cleared any prints in years. I only clear now when doing side by side testing of stuff or when calibrating gum with PDN because the dichromate stain can look deceptively like increasing maximum black/exposure in the PDN system when, in fact, the gum layer is hardened enough. Hence it will result in your thinking you need longer print times when, in fact, you don't. So clearing is a good idea when determining standard printing time to get your maximum "black" (or magenta, yellow, thalo...)...and, in fact, in all the PDN steps. That brown tone that gets successfully darker can be deceptive.

Once I tested how "maximum black" dichromate actually gets by leaving a dichromated gum solution outside in a cup in full sun for a day. It gets the color of dark molasses. Silly factoid you need to know :)

Hmmm...I should have mixed it with metabisulfite to see if the brown turned green...oh no, shades of reading years and years of "what is dichromate stain" arguments in the alt list archives must be getting to me.
Chris

Christina Z. Anderson
christinaZanderson.com

On Jan 17, 2012, at 5:10 PM, Johnny Brian wrote:
> Thanks. I have been using 1% metabisulfite as I do have some yellow discoloration. I'm reluctant to change much in the process as I created a calibration curve with PDN - and it seems to be working OK. What I was curious about was to how long should I wash the print after metabisulfite treatment. 
> Thanks, 
> Johnny Brian
>