For gumprinting I would use a gum "primer" layer without negative but hardened with UV light and fully developed followed by one or several gum layers with negative. Gum should not wash away on glass there even was a photo mechanical process called the Erwinotype/Erwinotypie that used glass with a gum matrix as printing plate. Look it up it really is an interesting process. For casein print I would use a sublayer of hardened casein just like with gum.
Thank you Dominik. Do you have a favorite method of cleaning the glass?