What are paint brush bristles made of ?

At the moment, paint brush bristles have two kinds, one is bristle, another one is pure synthetic.

If it is bristle, it would be pure bristle or bristle mixture synthetic, natural bristle is more durable and good painting holding and release, Natural Bristle is more suitable for oil-based painting. Bristle mixture synthetic is also better in oil-based painting. Natural bristle is more suitable for outdoor painting.

If the filaments are synthetic, they may be made of polyester, nylon or a blend of nylon and polyester. Filaments can be hollow or solid and can be tapered or untapered. Brushes with tapered filaments give a smoother finish. Synthetic is more suitable for water-based painting and indoor furniture painting,.