>Now my calculations say that 25 ml will only cover to a depth of
>.5mm. 20x25x.05 cm = 25cc = 25mm. Which is correct?? I seem to
>get good results using approximately 30 ml.
Don't know if this will help or not, but a while back I was sent a piece of
Hanfstaengl carbon tissue so I could see what it looked like. Out of curiosity,
I measured the coating thickness, and found it to be about 0.002 inches (0.05
mm) thick. I coated two 8x10 sheets with 100ml of gelatin, and ended up with a
film thickness of about 0.0025 inches (0.064 mm). My coating process was fairly
sloppy, so it definitely took less than 50ml to coat one 8x10. These coating
thicknesses were for the dry gelatin. I don't know how much the gelatin shrinks
as it dries.
One the other hand, unless you are trying to conserve pigmented gelatin, thicker
layers shouldn't hurt anything. You just need to have a sufficiently thick
coating so that the light hardening doesn't penetrate all the way through to the
tissue support. The excess gelatin is washed away during development.
- Wayde Allen
(74160.3410@compuserve.com)