A chemistry question (dichromate)

[M Carter]

Hey chemistry experts - this concerns the Bromotype process, but doesn't seem to ever have been a mention of that on Photrio, so thus trying here vs. the alt process forums for a start.

With Bromoil printing, you treat the print in a bleach made of copper sulfate, potassium bromide, and potassium dichromate, and is then fixed and washed. This bleaches the image back but also treats the gelatin to accept ink later. Bromotype is similar, except after the bleaching, you rinse and redevelop the print partially, leaving some silver image in the emulsion to work along with the ink. The articles I've read suggest the redev be done in weak developer.

I tried it this week, but was experimenting with holding shadows vs. highlights, and after bleaching and a decent rinse I immersed the print in straight paper developer. The highlights developed to black, giving me a negative image.

Could this have been an effect of full-strength development? I wouldn't think so, but I'm wondering if my book (Bromoil: A Foundation Course) has forgotten a step or something? Any clues would be welcomed, I'll give it another shot in the next week.

 

[koraks]

I've had similar things happen if I recall correctly with my experiments with different bleaches, and particularly with a bromoil dichromate bleach. That is, I experienced solarization, but that seems to be what you're having as well. Seems to have something to do with the copper sulfate, I suspect. I never really looked into it to be honest.

 

[M Carter]

Yeah, I've found two references to "bleach/tan the matrix per usual, but instead of fixing, re-develop". I'll have to give it another shot and watch every step of my process; but all the matrices I made that day (normally, without re-development) inked up fine.