الليقة السوداء الزاجية

Ingredients

العفص, الزاج القبرصي

Preparation Steps

Original Recipe Text

The process described is a two-step application (p. 139). First, galls (Afs) are ground and soaked in water. This solution is used to write on the paper. After the writing has dried, a second solution is prepared by grinding Cyprus vitriol (Zaj Qubrusi) finely and dissolving it in water. The paper containing the invisible gall-ink text is then dipped into the vitriol solution, causing a chemical reaction that makes the writing appear black (p. 140).

Evidence

"يؤخذ العفص، يسحق وينقع في الماء. وتكتب به في الورق... ثم يؤخذ الزاج القبرصي المليح، تسحقه ناعما، وتذوبه في الماء، وتغمس الورقة فيه ، فتظهر الكتابة سوداء"

Remarks

This recipe is a variant of the ferro-gallic reaction used for secret or sympathetic writing. The footnote on page 140 clarifies that the reaction is between tannic acid from the gallnuts and the metal salts in the vitriol.