Greetings! I hope this might be the best place to post this since it's probably more about coating unusual substrates with gelatin-type emulsion, but I am talking cyanotype instead of silver.

Basically I'm taking both an "alternative processes" (which means cyanotype, vandyke, chromo, lith, toning, lo-fi holga stuff) and a welding class. Obviously these two things are begging to be combined so I starting looking into ideas.

After some research, the first thing I want to try is coating metal (abraided finish aluminum) with cyanotype, but obviously that isn't going to work with the standard water soluble solution. I have read that if I get something like "photo grade" gelatin (such as Rollei/AGFA Black Magic Photo Gelatin, or some other 250 bloom gelatin), make a 20% to 80% water solution of that, then mix that solution 50% with 50% of the standard (already diluted and mixed) Ferric Ammonium Citrate and Potassium Ferricyanide solution, I can brush that on non-porous surfaces to make images.

The thing is that I'm a little confused as to the actual properties of how this stuff should work. Do I need some other coating under the gelatin-based coating for it to stick? Will it stick just fine if the metal has an extremely rough abrasive-like surface? Will the blue in the gelatin be opaque (or how opaque will it be?) and can I tone it just like paper prints?

Right now I'm thinking that the substrate will be something like sheets of 1/8" aluminum that have been scratched/scuffed/abraided/finished/etc with a rotary metal brush such that the surface of the aluminum is rough to the touch but still rather bright and metallic in a matte sort of way. This should mean that the base highlight "color" will be something approximating white and will look metalic, but won't directly reflect light like a mirrored surface. I'm already using this sort of substrate for emulsion lift transfers with Fuji FP-100C.

Can anyone give me some advice or point me to more information? Thanks