I am trying to do Tri-Color gum and can't seem to get a decent print. Most are to muddy in color after my 3 coatings.
I assume I just have to work with the individual pigment strengts to get the right set of pigment/gum strengths and also work with the exposure time to get a balance I like.
Wasn't there an article on this on unblinkingeye or something? I think that person was using a hybrid workflow, and they had gotten the optimal curves to use with the process characteristics to prevent crossover etc.
As I recall the critical factor was that the bottom dye could be opaque, but the top two had to be translucent. Not sure of the dye nomenclature but if the top dyes are opaque you won't see the bottom ones.
It takes a lot of research and trial and error to learn to do well with this process. The best information available is in Christina Anderson's book "Alternative Processes Condensed". She has done all the research and is a very thorough worker and teacher.
As far as the negative separations are concerned again you have to work on the curves until they work for you. I have one former student who produces 3 color gums that look like paintings. It took her about 6 weeks of experimentation to get the curves the way she wanted them.
Anyone who is successful with the process goes through the testing. You can not depend on someone else providing the answers for you.
I'll second the recommendation for Christina Anderson's book. There are so many variables besides the negatives - the paper, the sizing, the pigments, the pigment/gum ratio. It's a frustrating, challenging, fascinating process. If you did a workshop, and got good results there, you'll have to figure out which variable(s) is(are) different.
Yes, I have Chris's book, and took a wonderful workshop from her. I am now trying to get similar results at home. As you both said, there are many variable so I'll just keep printing until I get better results.
holmburgers, I think water soluble colorants aren't suitable for gum dichromate; just picture the leeching of dyes in the development stage; the principle of gum dichromate is trapping "pigment" "particles" in the "poriferous structure" of hardened gum - induced by the action of light on dichromate...