The treatises of Benvenuto Cellini on goldsmithing and sculpture

The first is colour for thin gilding. You take equal proportions of sulphur, tartar well-pounded, and salt, grinding them separately, then you take half a part of cuccuma[178] and you mix them all four together. When you have the gilded parts well cleaned & scratch-brushed, as I described above, you take a little urine of children or boys, put it tepid into a clean pipkin and apply it with hog sables, and the virtue of the urine and the sables will remove any dirt or grease that may have come on the gold. This done, you get a copper cauldron, or mayhap an earthen pot, & in one of the twain, after filling it with boiling water, you put your colour composition & stir it well up with a rod or a bunch of twigs till it is thoroughly dissolved and mixed. Then you tie a bit of string, long enough to hold it by, on to the work, and dangle it in for such time as one might say an Ave Maria; after this you pull it out and dip it into a vase of clear cold water. If it has not taken colour enough you put it back again into the hot water, and so on for two or three times till it be sufficient, minding, however, not to let it stay in over long or else it will turn black and spoil the gilding. This colouring matter is the weakest one can make and can only be used for one turn.