I make carbon transfer prints and the tissue for capturing the image is a suspension of 10% 260 Bloom gelatin, 4% sugar, 6 mi Thymol, 10 gm Glycerol & 68 gm of India ink per 4000 ml of solution.  I add 25 drops of 5% Tween 20 (polysorbate 20) to the suspension but the pigment falls out of suspension after it has been at approximately 110 deg. F. for an hour.  Would increasing or changing the polysorbate help?  www.freddusel.photography

Thanks, Fred