Dictionarium polygraphicum. Iris green, to make.

Dictionarium Polygraphicum:
Or, The Whole Body of Arts Regularly Digested.
Vol I.
London: Printed for C. Hitch and C. Davis in Pater-noster Row, and S. Austen in St. Paul's Church Yard. MDCCXXXV.
1735
Take of the bluest flower de luces, which are called otherwise flag iris, strip off the upper or fattin part of them, and keep only that; the rest is not good for any use in painting, and pick even all the little yellow nerves, and throw them away too; then pound what you have thus pick’d in a mortar, throwing three or four spoonfuls of water upon it, according to the quantity of flowers you pound; but you must first have dissolved in this water a little alum, and a very little gum Arabick; and having pounded them well together, strain all through a close cloth, and put this juice into shells, which dry, in the air.

Another way.
Pound your flower de luce flowers, pick'd as before, in a mortar, and press out the juice into shells, and salt the juice in each shell with alum a little unequally, and you will by that means have Greens of different shades.

Another way.
Pick the flowers as directed in the first, then pound them, and put to them a little alum water, and throw in a little powder of quick lime, as if you were salting a sallad. This will both change the colour and cleanse it.

Another better way.
Pound alum, and having bruis’d French or Avignion-berries, mix them with water, and boil them either over a fire or an ash heat, till the water becomes very yellow; then pound the flower de luces in a mortar, and pour a little of this yellow water upon them, according as you would have your Green, either bright or sad; then strain it through a cloth of goat's hair, for if it were pass'd through linen, it would not be so good; and put the juice so strained into large shells, and expose them to all the heat of the sun; for if they are set in the shade, the Green will become mouldy or mothery, and prove too clammy.

Another way.
Mince the leaves of the flower de luce or flag iris very small, and put them into a glass or earthen vessel; or rather into a copper pot or pan (which is better) with some alum and quick lime powdered; let them stand to purify in this state for ten or o days; and when they are rotten, squeeze them into ells.
The Green is more lively and rich when the Green is only pounded, and the juice squeez'd out at once, without giving them time to rot, having first salted them over with powdered alum.