Quercus infectoria Gallnut is used to mordant cellulose fibers and fabrics before the alum mordant is used. Alum does not combine as readily with cellulose fibers as it does with protein fibers. Fortunately tannic acid or tannin has a great affinity with cellulosed fiber and once mordanted with tannin, alum combines well with the tannin-fiber complex. Gallnuts (nutgalls) from the oak tree are the earliest and richest source for natural tannin (gallotannin).