Crystallized salts would form after the water had evaporated. Fluid was collected in large iron pans as it trickled out of the rock in mine shafts. In Goslar, Germany, a large concentration of natural vitriol supplied much of Middle Europe. Vitriol was obtained from different mines and obtained by various techniques. Vitriol was contaminated in varying degrees with metals that do not contribute to color formation in an ink solution. Both products were obtained from minerals which contained many other metals, such as copper, aluminum, zinc and magnesium. For centuries there was no distinction between these salts. Even more confusing is the close association between copper sulfate and iron sulfate. The latter term was used both for the salt and for the color that it produced with tannin. In Antiquity, vitriol was called chacantum ("blood of copper") by the Greeks and attramentum ("black" or "making black") by the Romans. Vitriol is also referred to in recipe books as of copperas, sal martis, sulfate of iron, copper red, English vitriol, Roman vitriol, vitriolum cyprinum, and vitriolum hungaricum. Cooking in a slightly acidic solution, like wine, will also produce gallic acid.(See color formation: chemical reactions) Hydrolysis of gallotannic acid can be accomplished by using acids or by letting the tannin solution ferment (leaving the solution exposed to air will rapidly result in mold growth on the surface), to produce gallic acid and water. It is the gallic acid groups in gallotannic acid that react with iron sulfate to create the colored ferric tannate complex. Gallotannic acid is the type of tannin most used for ink making and found in particularly high concentration in Aleppo galls. However, these plant materials contain far less gallotannic acid. (IMAGE) Tannin could also be extracted from other sources such as chestnut wood or bark, oak bark, the Sumach plant and pomegranate peels. Aleppo galls (Aleppo is a province in Asiatic Turkey), acorn galls, oak-marble galls, Chinese galls and Japanese galls were used most often for ink manufacturing. There are many different types of galls (thousands!), all with varying tannin content. When the larva or insect is still inside the gall, the tannin content is said to be higher than if the insect has escaped. Wasps that have not made it out can sometimes still be found inside the galls once cracked open. Small holes in galls indicate where the insect has made its escape. After the larva has developed into a wasp, it chews its way out of the gall. The gall provides both food and protection for the larva. The hatched larvae feed upon the tree, secreting an irritant that prompts the tree to create a growth around the larva. The female gall wasp, for example, punctures twigs on young oak trees to lay her eggs. Several kinds of insects can cause the formation of galls, including aphids, flies and wasps. Galls are created by parasites which lay eggs in various types of vegetation. There are different sources of tannin suitable for ink manufacture, but certain tree galls were known to contain a high concentration of this material. The term "tannin" has historically been used to describe a group of chemicals capable of tanning hides to make leather. Different products were included in the recipes over time, but using these ingredients alone will produce a fine ink. Iron gall ink is created from four primary ingredients: Tannin, vitriol (iron sulfate), gum Arabic and water.
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