Viradon

Viradon is a brown toner made by AGFA. It can also be used as a treatment for the archival of negatives and prints. It is a brown toner, based on the action of Sodium or Potassium polysulfide (Na2Sx) on silver compounds which will turn dark brown without the need for bleaching. The resulting colored compounds are very stable, thus the archival characteristics of the prints, especially when mixed with selenium. In the words of Rickard Knoppow "Because Polysulfide toners affect all densities equally they provide good protection to an image even when only partially toned. The current recommended toner for protecting microfilm is a Polysulfide toner. I don't know the life of the mixed toner."[1]

The original Viradon was introduced in the 1930s and contained both polysulphides and selenium and was used at dilutions of 1+50 and was similar to the original Kodak Poly-toner The formula of Viradon was modified in the year 2000 to comply with environmental regulations, becoming a brown poly-sulphide toner used in dilutions around 1+25 similar to Kodak's brown toner. The production and sale of Viradon was discontinued in 2012.

References

Rudman, Tim. 2002. The photographer's toning book. Argentum.

Rickard Knoppow - Discussion in pure-silver mailing list [1]