PDA

View Full Version : Subbing layers for gelatine dry plates



joshverd
11-26-2006, 06:57 PM
Hi,
I'm interested in getting better adhesion from my gelatin emulsions on glass. I have heard several types of subbing/hardener combinations, and I have heard others say they are not necessary(only a really clean plate is necessary). I have cleaned the plates *meticulously* and water sheets off of them, etc... Any suggestions as to how I can get my emulsion to not lift off during development?

Photo Engineer
11-26-2006, 08:32 PM
A properly washed emulsion should adhere to a well washed plate. Some frilling is to be expected though, but only around the extreme edges.

However, if you lightly sand or abrade the edges of the glass plate to put a tooth on the glass, this will reduce frilling. It can be done by scraping the edges of a glass plate against another, or by using a very fine metal file to gently bevel the edges and give a frosted appearance to the glass.

But if this does not solve the problem, you may not have washed the emulsion enough. Salts tend to increase the repellancy between the emulsion/glass interface.

Here is a good sequence.

Wash the plate in acid dichromate and then in detergent followed by a DW rinse. Then dry. Before coating, heat the plate to about 40 deg C or the temp of the melted emulsion. Use either chrome alum or glyoxal hardener. Add a small quantity of Everclear to the emusion (or ethyl alcohol). Moisten the warm plate with your breath. Then pour on the emulsion and coat.

Hope this helps.

PE

smieglitz
11-26-2006, 08:39 PM
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.

Joe

joshverd
11-27-2006, 05:39 PM
Thanks! I will begin my tests.

joshverd
11-27-2006, 08:08 PM
Hi guys, thanks for the feedback, I have yet to try these out.

I was talking with a friend, and they recommended that I prep the plates by dipping in a bleach solution, or by using a laundry detergent solution.

All of these seem to have something in common with the ones you guys shared above.

Basically do I just need a really clean plate, or do the processes you shared somehow chemically prep the glass to receive the gelatin(ie.: by leaving some residue bonded to the plate that the gelatin adheres to)? Also how do these processes my friend mentioned sum up with the ones you all suggested.

Hologram
11-28-2006, 03:15 AM
Hi guys, thanks for the feedback, I have yet to try these out.

I was talking with a friend, and they recommended that I prep the plates by dipping in a bleach solution, or by using a laundry detergent solution.

All of these seem to have something in common with the ones you guys shared above.

Basically do I just need a really clean plate, or do the processes you shared somehow chemically prep the glass to receive the gelatin(ie.: by leaving some residue bonded to the plate that the gelatin adheres to)? Also how do these processes my friend mentioned sum up with the ones you all suggested.

You might have a look into areas like lithography or holography, where there is some experience with the coating of glass plates.
Besides the aminopropylsilane thing there is the option of forming a very thin (gelatin) subbing layer. This can be done by dip-coating. The subbing solution is made of 4g gelatin and 0.4g chrome alum, dissolved in one liter distilled water.
Drying the plates at a warm place (> 50C) will greatly accelerate hardening.