Catechu

For the region in India, see Kutch District.

Catechu ( or ; also known as cachou, cutch, cashoo, Terra Japonica or Japan earth) is an extract of any of several species of Acacia&mdash;but especially Acacia catechu&mdash;produced by boiling the wood in water and evaporating the resulting brew.

Catechu (called katha in Hindi, kachu in Malay, hence Latin Acacia catechu as the type species which provides the extract) is an astringent and has been used since ancient times in Ayurvedic medicine as well as in breath-freshening spice mixtures.

The mixture is high in natural vegetable tannins (which accounts for its astringent effect), and may be used for the tanning of animal hides. Early research by Sir Humphry Davy in the early 19th century first demonstrated the use of catechu in tanning over more expensive and traditional oak extracts. The extract gave its name to the catechin and catechol chemical families first derived from it.

Black Catechu has recently also been utilized by Blavod Drinks Ltd. to dye their vodka black. 

Under the name cutch, it is a brown dye used for tanning and dyeing and for preserving fishing nets and sails. Cutch will dye wool, silk, and cotton a yellowish-brown. Cutch gives gray-browns with an iron mordant and olive-browns with a copper mordant.

White cutch, also known as gambier, gambeer, or gambir, has the same uses.