Grinding orpiment is most laborious, and in order to accomplish the task more easily and quickly, it is best to take a pepper-mill and grind the orpiment in that. When you have done so, put it on a marble slab, and then grind it with water, and treat it like the other colours which are being ground. As we have already stated, you may mix with the orpiment both indigo and terre-verte, and anything else which may be found (i. e. prescribed) in the recipes given above.