Ink that Writes in Black on White and White on Black

Ingredients

potash, water, antimony, marcasite, litharge, white lead, crushed gallnuts, iron filings, Arabic gum, starch

Preparation Steps

Original Recipe Text

Take good potash weighing four dirhams. Pour half a rotl of water over it. Stir it and leave it for seven days. Whenever the water decreases, add an amount equal to what was lost and stir it. After the days have passed, strain the water into [a vessel containing] eight dirhams of crushed antimony, three dirhams of marcasite, and one dirham of litharge. Grind them in a mortar for one day. Add four dirhams of white lead to it. Grind everything thoroughly. Pour three ounces of water over it and leave it for five days. Then boil the potash water and antimony, and the crushed gallnuts, weighing five dirhams, until one-third of the water evaporates and two-thirds remain. Strain and mix them. If it is used with iron filings, it is excellent. Then mix the water with the aforementioned ingredients, along with some Arabic gum and starch.

Remarks

It writes in black on white and white on black.