Liquitex Slow-Dri Gel Retarder is just like their Slow-Dri Blending Medium a medium to extend the drying time, to avoid stress and "dented" brushstrokes, but also to be able to mix and making it easier to fade from one color to another.áIt has no binding agent, so you should not mix the paint more than 25%, but it's a gel, so it's easy to mix directly on for example a palette. Flexible, non-yellowing and water resistant when dry. 237ml.