Failures And Part Succeses With Paint Blackening The Back Of Clear Glass Ambrotypes

I am refining the acrylic paint I am using and trying mixes with varnish to make the consistency of the fluid a bit less solid. One of the paints is drying with small cracks so trying to figure out why. I am trying one higher end artist acrylic as well, to see if it is worth the extra money. Am also doing 2 varnishes of plates today, a double varnish should theoretically add more protection to the collodion. 

An online friend (Borut P) also suggested albuminizing (egg white/distilled water coating) all plates. I like that idea. It would make the collodion stick that much better to the glass. The only down side is the plates would be harder to clean and reuse in the field. It is sometimes hard to remove collodion that has been attached with albumen.

The washable paint idea did not work at all, it destroyed the ambrotype, even with a coat of varnish on it.

Destroyed Ambrotype, washable black paint