Dr. Ph. Martin's Liquid 421 is a new kind of wetting/rewetting agent designed to increase the drying time and ease of blending for use with Hydrus Fine Art Watercolors. It can be used either as a precoat on paper before applying color, or mixed with color on palette. 

Comes in a 1.0 oz glass bottle with dropper. Liquid 421 is clear, non-staining, and non-toxic.

Currently only available as a beta product. Only available in the United States at this time.