Gum arabic

Gum arabic is a natural gum harvested from acacia trees and used as a binder in inks, gouache and watercolor paints. It holds pigment particles in suspension and helps them adhere to paper once the water carrying them evaporates, which is why many calligraphy inks and gouache mixes list it as an ingredient rather than relying on pigment and water alone.

For calligraphers, gum arabic often comes up when mixing gouache with water to a usable consistency, since gouache is a pigment plus binder that needs to be thinned before it will flow through a nib. Adding a small amount of extra gum arabic can improve flow and sheen, while too little can leave a chalky, uneven line, and too much can make the mixture sticky or slow to dry.

When buying gum arabic, look for calligraphy or fine art grade rather than industrial grades sold for other crafts. A common mistake is assuming all inks need extra gum arabic added; most bottled calligraphy inks are already balanced and adding more can throw off flow and drying time. It is most useful when mixing your own ink or gouache from raw pigment rather than using it as a routine additive to premixed ink.