The treatise revives and explains an ancient wax-based painting technique revived by Count de Caylus, combining historical enquiry with practical instruction. It opens with a discussion of Pliny's reference to painting with wax and summarizes competing experimental approaches, then gives a clear, step-by-step method: preparing and waxing the support, applying a powdered ground, using water-mixed pigments, and gently heating the finished panel so the wax absorbs and fixes the colors. The author compares results, reports on durability and appearance, reproduces letters and observations from contemporaries, and appends a straightforward technique for fixing crayon drawings.