There are lots of other selenium toners that are not quite like KRST. Some are direct, and others are bleach-redevlop types. One of the most famous is Flemish toner, marketed at one time by both Agfa and Dassonville. It is a bleach-redevelop type:
Dassonville T-7 selenium toner
Solution A - Bleach
Potassium ferricyanide 30 g
Potassium bromide 30 g
WTM 1 l
Solution B - Redeveloper
Sodium sulfide 40 g
Selenium (powder) 1 g
WTM 1 l
Dissolve the sodium sulfide completely, then add the selenium and heat until dissolved.
Use the bleach full strength. Bleach the print completely.
Dilute the redeveloper 1:10 for use. Redevelop until the desired tone is reached. Wash for one hour after toning.
A similar toner was marketed by bothe Kodak and Dassonville as T-56:
Kodak T-56 Sulfide-Selenium Toner
Solution A
Potassium ferricyanide 50 g
Potassium bromide 50 g
WTM 1 l
Solution B
Water (52C) 750 ml
Sodium sulfide 250 g
Selenium powder 5.7 g
WTM 1 l
Bleach print in solution A, then wash until yellow stain is removed.
For use, dilute solution B 1:20. Redevelop bleached print in this solution, wash again, and dry as usual without heat.
Among the direct toners is this:
Direct selenium toner
Selenium powder 1 - 4.6 g
Sodium sulfide 50 g
Water 480 ml
Heat water to dissolve selenium. Filter resulting solution. After toning, treat prints with 2 or 3 baths of a one percent sodium sulfite solution.
The tone is a purplish brown. Less selenium in the mixture produces browner tones.
Powdered selenium is available from chemical suppliers, but it is not always easy to get in small quantities. It is quite toxic and is an inhalation hazard. Be careful.