The flag, the delicate split-end of each bristle tip, if damaged opens the bristle's hollow shaft to capillary drying of its natural oils. The brittle bristle then breaks. Stroking the brush across the smooth aluminum coil screen submerged in Silicoil Brush Cleaning Fluid effectively exposes oil colors in the brush to the fluid's cleaning action. The color solids settle to the bottom, the flag is undamaged, the brush is properly cleaned, and will remain pliable indefinitely. Acrylic and other water-based colors are easily cleaned from brushes using clear water.