Page:Cyclopedia of Painting-Armstrong, George D (1908).djvu/176

168 more even in thickness than the ordinary gold, and put up in books of special paper that does not require dusting with French chalk or Armenian bole to prevent the gold adhering to the book. The gold thus supplied is much cleaner than that used for general purposes. It is important that glass gilding be made to dry off quickly and that no time be allowed to elapse between the operations, or it will accumulate dust and get discolored.

Although gilding on glass is looked upon as a difficult matter to successfully carry through, all the difficulties are overcome by the exercise of cleanliness. The cleanliness of the glass may be tested by breathing on it, and if the moisture evaporates quickly, leaving the glass clear, it will do. Glass may be made chemically clean by the use of dilute nitric acid, and well rinsing with water.

Tissue paper is a good glass polisher. Filtered rainwater makes the best isinglass size, or distilled water, as it is free from metallic taint.

Gilding upon paper, parchment, and vellum can be best done by using a size made from yolk of eggs and glycerine. This is ground together with a little ochre and thinned with water. If used in a very liquid state as a mere water wash size, and the gold is laid directly thereon, as in glass gilding, it may be tooled or burnished. All gold work should be sized before writing or painting upon it.

Platinum and Silver Laying and Metaling. Platinum leaf is used in the same manner as gold lead, and is applicable to all the same purposes.

Silver leaf and gold leaf of very pale tint, that is, which contains a large proportion of silver, should never be laid on the oil gold size, neither should metals which are subject to oxidization, as the oil has a strong affinity for oxygen, and the oxidization of the metals is set up and goes on more rapidly. If used upon a spirit size or water size, and well protected with lacquer or spirit varnish, these metals will be perfectly lasting. Their durability depends entirely on