I have made it my concern to hunt out this technique for your study as I learned it by looking and listening. On Divers Arts, c. 1122, is the oldest extant manual on artistic crafts to be written by a practicing artist. Before Theophilus, manuscripts on the arts came from scholars and philosophers standing outside the actual profession. On Divers Arts describes actual 12th-century techniques in painting, glass, and metalwork, which the Benedictine author wished to pass on to those gifted by God with a talent for making beautiful things.
Theophilus teaches, with rigorous attention to fact but also with great reverence the making of pigments for fresco painting, the manufacture of glue, the technique of gold leaf on parchment (the first recorded European reference to true paper), how to blow glass and design stained glass windows, how to fashion gold and silver chalices, and how to make a pipe organ and church bells. Precise instruction on enameling, chasing, repoussé, niello, and beaded wire work prove Theophilus's first-hand knowledge of his craft.
While 90 percent of Theophilus's writing is sound technical knowledge, medieval folk lore occasionally spices his text: Tools are also made harder by hardening them in the urine of a small red-headed boy than by doing so in plain water. But the magnificent fact of On Divers Art remains its status as the first technical treatise on painting, glass, and metalwork, for which actual specimens still survive. The editors have taken care to ensure both philological and technological accuracy for this authoritative edition of a medieval classic, a manual of great importance to craftsmen, historians of art and science, and all who delight in the making of the beautiful.