A mop artist's paintbrush, size 6, with synthetic fibres made from polybutylene terephthalate (PBT). A mop brush is typically used with watercolours to produce an even wash of colour over a large area or for softening and blending techniques. Squirrel or goat hair is particularly suitable for this type of brush but the Raven is a vegan alternative from Jackson's. Using filament manipulation technology, millions of tiny indentations are created in the PBT fibres to increase the surface area for greater pick-up and release of paint/water. The fibres are then treated to remove any static electricity so that they do not stick together and will move smoothly and precisely. The Raven includes a mix of 'dull' and 'full-dull' fibres.