Gallnut is used to mordant cellulose fibres and fabrics before an alum mordant is used. Alum does not combine as readily with cellulose fibers as it does with protein fibers. Fortunately tannins have a great affinity for cellulose fibre and once mordanted with tannin, alum combines well with the tannin-fiber complex. Gallnuts (nutgalls) from the oak tree are one the earliest and richest source for natural tannin. They are produced by insects that deposit their eggs in small punctures they make on young branches. The tree excretes a tannin-rich substance that hardens and forms into a gallnut. These are collected and ground for use as a tannin mordant. Gallnuts are used in the leather tanning industry, and for in some medicines. Use at 10-12% WOF. Use 6-8% WOF for Gallnut Extract.