Gall
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Galls or cecidia are a kind of swelling growth on the external tissues of plants. Plant galls are abnormal outgrowths of plant tissues, similar to benign tumors or warts in animals. They can be caused
Cola-nut galls (Andricus lignicola) on pedunculate oak, caused by a cynipid gall wasp
Oak artichoke gall caused by Andricus foecundatrix
Artichoke gall cut open to reveal wasp larva
Knopper gall caused by Andricus quercuscalicis
Iron gall ink
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Iron gall ink is a purple-black or brown-black ink made from iron salts and tannic acids from vegetable sources. It was the standard ink formulation used in Europe for the 1400-year period between the
Gall
…cynipid wasp Belonocnema treatae. Galls are rich in resins and tannic acid and have been used widely in the manufacturing of permanent inks (such as iron gall ink) and astringent ointments, in dyeing, and in leather tanning. The Talmud records using gallnuts as part of the tanning process as well as a dye-base…
Oak galls and iron(II) sulfate, ingredients of iron gall ink
Homemade ink. On left, a solution of iron (from nails) and vinegar. On right, oak extraction. The two are mixed immediately prior to use to produce the ink, centre.
Homemade iron gall ink in use, displaying the delayed darkening of the ink
Ink corrosion: iron gall ink causes paper and parchment to disintegrate