Pliny discusses the processing of the gland, or vein , and the dyeing stage in the following passage: Subsequently the vein of which we spoke is removed, to this salt has to be added, about a sextarius [Roman pint] for every hundred libras [Roman pounds]; three days is the proper time for it to be steeped, as certainly the fresher it [the extract] is the much stronger it is, it should be heated in a leaden pot, and with a single amphora [48 sextarii ] of water to every quinquagenas [fifty] libras [Roman pounds] of dye and kept at a uniform and moderate temperature by a pipe brought from a furnace some way off. This will cause it gradually to deposit the portions of flesh that are bound to have adhered to the veins, and after about nine days the cauldron is strained and a fleece that has been washed clean is dipped for a trial, and the liquid is heated up until fair confidence is achieved. A ruddy color is inferior to a blackish one.
