Natural vs Synthetic Bristles:
Paint brushes with natural bristles are meant for oil-based paints. The newer Synthetic bristles can be used for anything but were really designed for water-based paints. Natural bristles will soak up the water and go limp in water-based paints.
Badger or Ox hair Bristle:
These brushes feature the softest natural bristle. Best for creating glass-smooth finishes with oil enamels and varnishes.
White China Bristle:
For oil-based paint, stain, varnish and polyurethane, as well as shellac and lacquer, we recommend using a paint brush that features these bristles. Soft natural bristles yeild a smoother finish than a black china bristle.
Black China Bristle:
For oil-based paint, stain and varnish. Bristles are stiffer and may require more forceful stroke to get the paint onto the surface but the least expensive natural bristle brush.
Paint brush's performance depends upon the bristles. A quality brush will have Solid filaments as opposed to hollow. Bend a filament at the base and solid ones spring back while hollow won't. Densely packed bristles that taper to a chisel edge help with painting a straight edge, cutting in or tipping. Split ends or flags hold more paint and spread it more evenly and smoothly.