Re: Making very thick tissues

>Sandy postulates:
>
>However, when I later sensitized and exposed the dry tissue I found that
>the gelatin had become almost completely insoluble, and as far as I am
>able to determine from my tests, the increase gelatin percentage (from my
>normal of 8% to 20%, and the thickness of the coating) are the only
>changed variables.
>Does anyone have any information about how gelatins work to comment on the
>results of my tests?

This is unexpected. My theory is you should be able to make a good print on
tissue with 10 mm of gel on it. Maybe in theory 1 meter thick though a bit
hard to handle!

Here's my guess: The extra thickness is causing it to not dry thoroughly.
The carbon manual recently posted talks about "spontaneous exposure" due to
tissue not being thoroughly dry. (Ok wiseacres, it is never really dry
but..) The extra thickness may in fact be retarding the drying. Perhaps in
a non-linear fashion.

Here's a formula I've used for making a machine coated paper that has
worked fine. Mind you machine coating is a whole different animal as you
need a very quick set time. It probably would not work on lay down. But
note the sugar!

2000 ml water
200 gm gel -- blooming at 250
200 sugar -- YUP!
70 glycerine
200 pigment mix

--Dick
Received on Wed Dec 26 12:03:42 2001