Quote Originally Posted by keesbran View Post

This is very good news! And your site is very impressive too. Did you observe sensitivety differences or the need to adapt your negatives with DAS compared to dichromate?
And thanks for the spectrometer data.

Hello Kees,

The collotype is not my work. (But I would like to try the process) So I don’t know how they have to adapt the process.

For carbon print:
I changed too many parameters to directly compare the results with DAS and dichromate. (I’m still on my way to learn the process of carbon printing)
The sensitivity changes a little but the exposure time is in the range of some minutes with my “face tanner” UV light (~50cm distance).
I have the impression that DAS is working a little softer, but I might be wrong. The gamma can be influenced by the amount of DAS (as reported before) and also by the amount of pigment. I think the gamma should be directly proportional to the amount of pigment. With high amount of pigment it gets of cause difficult to distribute it equally in the glop. (I start with glycerin/pigment/some water and use a glass muller).

For a formula like this:

500mg lamp black (Kremer pigments 47250 Flammruß)
~1ml glycerin
~1g sugar
35ml water
150mg DAS (in 5ml water)

on 17cmx25cm Paper

I get a gamma of 0.7-0.8 on a transparent support. That should lead to a reflective gamma (on a paper support) of about 1.5. So it is in the range of silver-gelatin paper.