Holbein Masking Fluid Pen is a versatile tool to block out areas of an artwork when using watercolour or airbrushes. This Masking Fluid Pen is perfect for masking out fine areas of your artwork. Let dry well, then remove by rubbing with eraser or peeling off. Dries with a pink tint so it can be seen easily. Squeeze bottle with 8mm tip. The masking fluid will retain the white of the page or previous colour, that has been painted.