To an emulsion after Monckhoven's method, I add, before filtering, above eosine solutions to 1,000 c.c. emulsion, 15 c.c. each of yellow shade and 15 c.c. of blue shade eosine; mix with a glass stirring-rod, filter, and begin the flowing of the plates. On the contrary, to an emulsion made after Henderson's method, double the quantity of coloring matter can be added before flowing, without reducing the sensitiveness perceptibly.
Cyanin and eosine mixtures I give in the following proportions;
III. 0.5 grm. cyanin (iodo-cyanin) dissolved in 1,000 c.c. alcohol under good shaking.
(All coloring matter solutions have to be filtered.)
To 1,000 c.c. Monckhoven emulsion I give:
25 c.c. eosine solution, yellow shade (I.).
5 c.c. cyanine solution (III.).
With Henderson emulsion I increase to double the quantity.
Further experiments taught me that even if 60 to 80 c.c., and more, of these coloring matter solutions were added, and the emulsion was left to coagulate and then laid in alcohol for several days, after which it was washed well, so that hardly any coloration could be observed, it showed, when making a copy of an oil painting, that the color sensitiveness of the emulsion was not reduced, and that it had rather increased in relative sensitiveness.
Anyhow, I put every colored emulsion for eight days in alcohol, having experienced that hereby, after washing, just a sufficient quantity of the coloring matter will remain as is necessary for the color sensitiveness.