On VARNISH.
Varnishes are not required, as has already been observed; but as our eyes have been used so much to see colours, not in their natural hue, but disguised by varnish, those that should like to please themselves in this point may use the following method.
First lay on with a clean spunge a substantial lay of the white of eggs, and work it well upon the picture. This dry, lay on any varnish commonly used for oil painting, and your picture will look as if painted with oil-colours.
This varnish may be taken off at pleasure, the uppermost by rubbing the surface of the picture with a rag dipped in spirit of wine or turpentine, the white of eggs by washing the picture with water. It is not adviseable to lay a varnish of spirits or gums, without first using the white of eggs, as spirit of turpentine is the menstruum of wax.