You might try a silane compound. Bostick and Sullivan sells one.

I sub my wetplate glass with albumen and distilled water. One egg white in a half liter of water thoroughly frothed and filtered works. Or, you can dip a cotton swab in an egg white and then dip it in the water. That also seems to work.

The edge of each plate is roughened either with a whetstone or coarse sandpaper to give about a 45 degree angle to the upper edge. Then, after cleaning the plate thoroughly with a whiting + ethanol solution I run the cotton swab loaded with the albumen mix around the edge of the plate so that it comes in about 4mm.

That works for wetplate collodion. Whether it would work for gelatin dryplates is another story. But it is a fairly simple procedure and wouldn't take too long to test.