Watercolor Mediums

Watercolor mediums change the working characteristics of paint, or of the surface that you are painting on. Use watercolor mediums to extend drying time, to increase brilliance and transparency, to alter the absorption of the surface.

Gum arabic, the binder used in traditional watercolors and gouache, is a natural gum derived from the acacia tree of sub-Saharan Africa. It is completely non-toxic as well as edible, and its major use is in the food and cosmetics industries.

It serves as an ideal binder for watercolors because it dissolves so easily in water, yet dries to form a thin layer that binds pigment to a paper surface. Add additional gum arabic to watercolors to increase their transparency and gloss, while extending drying time.

Masking fluid prevents the paper from absorbing color. Use a watercolor mask before you apply a wash to protect areas that you want to remain white. Peel away the mask when it is no longer needed.

Most masking fluids use natural latex or a synthetic compound with very similar characteristics. They may contain an artificial colorant so that you can easily identify the areas you have masked.

A wetting agent is a substance that reduces the surface tension of water. It helps watercolor paints to spread and blend more easily, to penetrate the surface of the paper and its sizing. Watercolor paints contain wetting agents to increase working time and prevent them from drying out.

The traditional wetting agent used by watercolor painters is oxgall, extracted from the gall bladders of oxen as a byproduct of meat production. Modern synthetic wetting agents are also available.