“Take white Punic wax, melt it with oil, and while it is hot wash the painting over with pencils, or fine brushes of bristles, dipped in the same varnish. When laid on it must be well rubbed, and heated again with red-hot coals of gall-nuts, held close to it, till the wall may sweat and fry again, then rub it well with waxed cloths, and then with clean linen cloths[268].” This, I believe, is the longest and clearest account we have of this method of painting or rather varnishing. But there is another passage in the same author, from which it would appear that colours were made up with wax for use. For that case the above varnish would be most appropriate, and without the inconveniences of such varnishes as are composed of matters which do not correspond with the nature of the colours and vehicles they cover. The passage is as follows: “If one be disposed to make black wax, let him put thereto--i. e. to bleached Punic wax--ashes of paper, like as with an addition of orchanet, it will be red. Moreover, wax may be brought to all manner of colours for _painters_, _limners_, and enamellers, and such curious artificers, to represent the form and similitude of anything they list. And for a thousand other purposes men have used thereof, but principally to preserve their walls and armours withal[269].” We know, then, that the ancients used water, white of egg, solutions of various gums, vinegar and wax, with or without oil. We may infer also that they used solutions of resinous substances in oil, asphaltum, and petroleum, because they were well acquainted with preparations of these, and their application to a variety of purposes. But it would be rash as useless to assert that they painted with this or that material, having no positive information on the subject, and no examples of antique pictures, which can do more than indicate the nature of their works in fresco or distemper. Mr. Raspe, in his ingenious essay on oil painting, as known to the ancients, has laboured to prove too much, and has therefore not received all the credit he deserves[270]; but his printing the text of the monk Theophilus, and of part of Heraclius on the arts of the Romans, deserves our gratitude[271]. Both these authors direct, that colours for painting doors, and for preparing panel for pictures, should be ground in linseed oil; and they observe, that all kinds of colours bear grinding in oil. But all cannot be ground with gum, and therefore white and red lead and carmine must be ground with white of egg, where oil is not used. When a transparent painting was required over a ground of oil, then colour mixed with linseed oil was absolutely necessary[272].