Paint Application Problems II: Brushing

摘要

Brushing is one of the oldest ways of applying paint, probably only being preceded by daubing with a finger or a stick. A brush was a considerable advancement because it held paint as well as applying it. The spaces between the bristles act as a reservoir as the brush is dipped in the paint. Paint pick-up is a low stress, low shear process (~ 15-30 sec~(-1)), but brushing itself is a complicated high stress and high shear process (5,000 to 20,000 sec~(-1), depending on the brushing speed). When the paint is applied, pressure forces paint out from between the bristles. The forward motion of the brush splits the layer of paint, so that part is applied to the substrate and part remains on the brush.