Gevil

Gevil or Gewil (Hebrew: גוויל‎) is animal hide that has been prepared as a writing material in Jewish scribal documents, in particular a Sefer Torah (Torah scroll).

According to most views of Jewish Law, a sefer Torah (scroll) should be written on gevil as was done by Moses for the original Torah scroll he transcribed. Further, a reading of the earliest extant manuscripts of the Mishneh Torah indicate that gevil was halakha derived from Moses and thus required for Torah scrolls.

Maimonides wrote that it is the law transmitted to Moses on Mount Sinai that a Torah scroll must be written on gevil or alternatively on klaf and that scrolls written on an alternative material are invalid for use, however it is preferable that they be written on gevil (Maimonides, Hilkhoth Tefillin 1:14).

Definition of gevil

Gevil is a form of skin made from the whole hide, after the hair is removed. The precise requirements for processing gevil are laid by the Talmud, Geonim and Rishonim. They were reconfirmed as "the law according to Moses" by Maimonides, in his Mishneh Torah. According to law, the preparation of gevil hide must include salt, flour and mey afatzim (wasp residue/gall-nut water). Gall nuts—rich in tannic acid—are a tree's reaction to an invasive parasitic wasp's egg; the pure black tint of the ink used on Torahs results from the reaction between the tannic acid and iron sulfate (a powder used to make the ink).