Permanent Masking Medium is used to mask specific areas of the paper making them resistent to water. This medium can also be mixed with water colours and is ideal for isolating areas of fine detail. Sections which have been treated with Permanent Masking Medium must be allowed to dry before overpainting. A Hair dryer can be used to speed the drying. Once dry these areas remain protected and cannot be fully penetrated by further washes. Permanent Masking Medium can be applied directly to white paper, to dried washes on the paper mixed with water colours first. All water colour washes mixed with Permanent Masking Medium remain open and workable whilst the wash is still wet. Once dry, the area becomes isolated. Brushes should be washed in warm water and soap before using other colours.