Catalyst Polytip Bristle brushes are a Princeton breakthrough that advances the science of synthetic hair. This new series is super stiff yet extremely responsive. Unlike natural hog bristles, Catalyst has real integrity in water, natural bristle can be rendered useless when it is water-soaked. The true star of the Princeton Catalyst brush is Polytip, the tip of each individual hair has been split to replicate the natural flags on the finest natural bristle. By giving each hair 2 to 3 individual tips, Catalyst is able to hold a higher volume of paint while providing a smoother application. Designed for use with medium to heavy body acrylics and oil paints, Catalyst is even strong even to push heavy gel mediums with ease.