casein alternate?

[Gary Beasley <beasleyglb@mindspring.com>]

I was thinking of my experiences with coating and exposing silkscreens with 
photosensitive emulsion and I'm wondering if anyone has ever tried using 
that to mix colors into, coat and print like the casein based materials 
I've seen described on the list. The silkscreen coating looks a lot like 
casein glue before the sensitizer is mixed in and I know it will wash out 
incrementally thinner layers when exposed under a stouffer scale. I just 
never thought to try it like that when I was working in that field.