This topic has come up before so, it would be a good idea to
go back through the list archives
http://www.zilker.net/~gwalker/altphoto/
Getting a "strong" adherence of gelatine to glass and/or plastic is
somewhat problematic. My first experience with this was in trying to coat
pigmented gelatin on overhead projector slides. It looks good as long as
it is wet, but once dry starts to separate. This is why Pollmeier Klaus'
method of making carbon tissue by what I've called the "inverted casting"
technique works. Basically, you need to create some sort of sub layer
that adheres well to the glass, and that will also give good adhesion to
the gelatin coat that is applied on top of it.
There are many recipes for various such coating schemes. One of which is
listed in Crawford's Keepers of Light book under the section for making
colotype plates. This method makes use of a pre-coat with a dilute
gelatin solution. I assume that this allows some of the gelatin molecules
to bond to the few useable sites on the glass and serve as anchors for the
heavier gelatin layer, but that is only my theory.
Roughening the surface does help some, but not as much as I had
anticipated. At least that was my experience working with plastic. You
may also not want the frosted surface that this would create. The gelatin
pre-treatment definitely improved the adherence of the gelatin coating on
my plastic sheets. I only got separation after about a month, and then
only by forcibly flexing the sheet. If I remember correctly, someone on
this list working with culture plates or electrophoresis also suggested
the weak gelatin pretreatment.
Other substrate possibilities that were suggested were: collodion, and
albumen. I think that Keepers of Light also mentions stale beer. I
haven't tried any of these last suggestions.
Hope this helps a little bit. I'd be curious about any of the techniques
you may try, and your results. I'm also curious about how successful
you've been at making Lippmann plates? I was visiting with the local
Daguerreotypist's here in Boulder about a week ago, and we got into a
discussion about the Lippmann process. We were thinking it might be fun
to try. Any suggestions and/or pointers?
- Wayde
(wallen@boulder.nist.gov)