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An abnormal growth on trees, usually oaks (Quercus infectoria) in Europe and the Near East and on sumacs (Rhus semialata) in China and Japan. Galls are formed when gall-wasp eggs are deposited on tree branches. The nutlike gall grows until the larvae are completely enveloped. The mature insect bores a hole through the gall in order to escape. Bluish-green galls, gathered before the insect escapes, are richest in gallotannic acid, though all galls contain 36-60% tannins. The tannins have been used for centuries for vegetable tanning of leather. When galls are combined with ferrous sulfate, a black dye is produced; alone, they produce a gray dye. Gall extract was also used as a mordant in the preparation of writing inks.



Synonyms and Related Terms

galls (pl.); Gallapfel (Deut.); agallas (Esp.); noix de galle (Fr.); galla (It.); galappel (Ned.); noz de galha (Port.); nutgalls; gallnuts; noix de galle; oak apples; oak gall nuts; huur nuts; tamarisk gallo; pistacia gall; aleppo gall; Chinese gall; gall-nuts

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Sources Checked for Data in Record

  • Ralph Mayer, A Dictionary of Art Terms and Techniques, Harper and Row Publishers, New York, 1969 (also 1945 printing)
  • Hermann Kuhn, Conservation and Restoration of Works of Art and Antiquities, Butterworths, London, 1986
  • Matt Roberts, Don Etherington, Bookbinding and the Conservation of Books: a Dictionary of Descriptive Terminology, U.S. Government Printing Office, Washington DC, 1982
  • Encyclopedia Britannica, Comment: "gall" Encyclopædia Britannica [Accessed October 9, 2001]. (picture)
  • F. Crace-Calvert, Dyeing and Calico Printing, Palmer & Howe, London, 1876
  • Judith Hofenk-de Graaff, Natural Dyestuffs: Origin, Chemical Constitution, Identification, Central Research Laboratory for Objects of Art and Science, Amsterdam, 1969
  • J. Thornton, 'The Use of Dyes and Colored Varnishes in Wood Polychromy', Painted Wood: History and Conservation, The Getty Conservation Insitute, Los Angeles, 1998