Oxgall has been used in watercolor for hundreds of years, and it's still found in today's recipe for Schmincke Horadam Aquarell. This animal-derived liquid is a pre-industrial wetting agent — a substance that lowers the surface tension of liquids, making them flow, separate, and stain more freely. Wetting agents are what make watercolors so exciting in wet-on-wet painting; when you see watercolor rush into a wet area of paper, you're looking at the effects of a wetting agent of some sort.

Some manufacturers have switched to synthetic surfactants in their watercolor recipes, but oxgall is still found in many watercolor studios around the world. It's an essential additive that allows for unique granulating effects, rapid wet-in-wet movement, and super-thin, ethereal washes.

Packaged in a 60 mL glass bottle. Made in Germany.