Made from bovine gall, oxgall is a surfactant that traditionally is mixed with water-based marbling colors to help adjust their flow over the surface of the size. Oxgall is often the first line of troubleshooting defense if you find your colors sinking or otherwise acting out.  Instructions for use included.

Colophon’s oxgall is comprised of bovine gall that is collected, prepared, preserved in alcohol, and aged at least 9 months. Shelf life is indefinite, and in fact its working qualities improve with age. Store tightly capped. Sold in 2oz bottles or by the pint.