Gum develop

Hello all. I've just done the development of the yellow part of a CMY gum dichromate and all went well except in one area where the yellow should have held but instead part of it 'slipped off' the picture. Is it because I agitated too much or didn't develop enough ? The picture appeared developed OK before I soaked it. It's strange because in the same area, some of the yellow was OK and held as it should.

SPG

If it was in a heay yellow area, you may not have exposed enough. Yellow requires more UV than C or M.

It could also be a coating or sizing issue. That's the amazingly frustrating thing about gum - it's the most unpredictable process. In any case, you'll have to start the print over again, so I'd be extra careful when sizing the next piece of paper. Are you pre-shrinking and sizing your paper before you coat? If you are not sizing, it could be some imperfection in the paper is preventing the gum from adhering as well as it should. If you are, it could be uneven sizing is creating spots where the gum doesn't bind well to the paper.

It was me being impatient; something I'm going to have to curb for this process !

SPG

Hi,
Just a thought - I have more problems with emulsion detaching and marring when I use too much pigment. Maybe wind that back a little. Don't be to worried about getting too 'thin' a layer - you can easily add a K layer to bring in extra density and contrast.
I also solved these problems by exposing longer and developing longer as well.
B