adhesion

Adhesion of coated materials is determined by intermolecular force of
substrate and the material in the coating. The adhesion of multiple
layer coating is basically the same. Such a vague characterization as
"tooth" is a poor predictor of adhesion. Surface roughness may help
through increased area of contact, but roughness itself is not
sufficient for good adhesion.

Gelatin has good adhesion on many substrates including smooth glass
because of many available carboxyl groups. There is a kind of gelatin
where available carboxyl groups are increased through chemical
modification. This type of gelatin has particularly excellent
adhesion. My emulsions and sizing solutions contain this type of
gelatin and the coated layers give me excellent adhesion. When I coat
this type of emulsion directly on unsubbed glass, emulsion sticks to
the glass very well and I don't experience frilling. People who use
glass as the substrate may find it very useful to use this type of
gelatin as a part of the subbing layer and/or the emulsion itself.

--
Ryuji Suzuki
"People seldom do what they believe in.  They do what is convenient,
then repent." (Bob Dylan, Brownsville Girl, 1986)