Pebeo Drawing Gum 45ml

Basically Art Masking Fluid, but a slightly runnier and (within a short period of time) easier to remove.

Natural latex based masking fluid used to keep areas of artwork free from paint and is to be used with ink, watercolour and gouache. It is best applied with either a brush or pen on the parts of artwork that you wish to be masked. Colour is then applied once the drawing gum is dry. Once the colours are completely dry, simply rub the gum with either your finger or an eraser to reveal the masked parts.

It is not recommended that this is thinned - it should be used as is, straight from the bottle. 

Also available in a pen.