Today I engaged in further experimentation with Thiourea toning. I changed the mix that I used in my earlier article from 20/20/400 to 10ml Thiourea, 40ml Sodium Hydroxide, and 500ml water. The tone was not the yellowish brown of sepia but a much richer chocolate brown. The dark shadow areas were the color of coffee while the midtones are more of a milk chocolate color.
I of course had to make one mistake – I used a Dicromate bleach normally used for bromoil preparation instead of the Ferricyanide-bromide bleach typically used for print bleaching. It did not seem to matter. The white borders of the papers did take on a purple cast when wet but that disappeared once dry.
I tried the toner on several different papers from my recent experiments with LPD vs PF106. All toned about the same except for Ilford Art which has a more matte appearance and seems much lighter in the shadows.
Overall I am pleased with the tone and may like it better than the dark selenium tones, especially on Ilford MGFB Classic which tends to turn purple-ish with selenium. Below is a sample of the toned vs untoned areas on a test print. The banding left to right is the different exposure times and the dimpled texture is due to the scanning of Ilford Art paper.
Appalachian Trail – Byron Herbert Reece – Tunnel and Creek