Colourless Art Masking Fluid works by direct application to the paper. It can be applied to white paper or previously coloured areas. As it is latex based, colourless art masking fluid is best applied with an old brush or better still a quill or nib as the latex will peel off these. Brushes should be washed immediately in warm soapy water. It should not be diluted before use and should be removed as soon as possible once the painted area is dry. The dry fluid can be removed by rubbing with an eraser.