Re: a propos of gelatine

s carl king (sanking@hubcap.clemson.edu)
Wed, 15 May 1996 19:35:16 -0400 (EDT)

On Thu, 16 May 1996, Judy Seigel wrote:

Judy:

I am very interested in your work with liquid light because I just
re-did a 12X2o plate holder for my banquet camera and am thinking
about coating some glass plates with an emulsion. Was at first
thinking of wet plate collodion but liquid light sounds much
easier. I am not sure if I can really answer the questions you
raise below because the applications are so dissimilar to my work,
but here is a shot.B
>
> 1. It says use 1 teaspoon of gelatine to a pint (500 cc) of water. This
> is surely an error, because that's 4 grams, or less than 1% solution,
> which doesn't do anything, doesn't even set when cold. I figure at least a
> 3% solution, but can someone say for sure? a

The instructions may be correct, assuming you will be coating a paper
surface. If you are going to apply the gelatin subbing surface to glass
you will need to have a % solution strong enough to set within a reasonable
period of time, say 3-5 minutes. I would say about a 7% solution of 175
bloom gelatin is about as low a % as you can go and still get it to
set within this time frame. Also, you will need to level the glass on
which the coating is to be applied.
>
> 2. For each ounce of gelatine solution, instructions are to add 10 drops
> of a hardener bought separately for $2 per ounce. Since large amounts of
> gelatine are required to dunk big items, and since I have a jar of the
> stuff in question (Chromium potassium sulfate, or chrome alum) it would be
> a significant saving to mix our own. But we haven't a clue about the %
> solution. I'd guess saturated, or nearly so, but.......?

For every 500 ml of gelatin solution add 50ml of a 5% chrome alum
solution, or 50ml of formalin.

Hope this helps. >

Sandy King Sanking@hubcap.clemson.edu