Hi all, Many thanks for all the help. I am a biologist, so, there's generally numerous dyes that are readily available to me. Concerning erythrosine, which one should I get: Erythrosin B (2) Erythrosin B (1) Erythrosin B isothiocyanate, isomer II (1) Erythrosin B sodium salt (1) Erythrosin extra bluish (1) Erythrosin yellowish blend (1) ACID RED 51 (ERYTHROSIN B C.I. 45430) (1) also, formalin, should I use it before coating? And would a few drops of 40% in 20ml suffice? Also, the erythrosin, can I add a few milligrams to the gelatin (in case of powder) also before coating? Many thanks again for the help. Also, if anyone would have the time, if one has the following stais available: http://www.sigmaaldrich.com/catalog/search/TablePage/14577443 Which one (if any) you would recommend for a yellow and/or green sensitizers. Many many thanks.