make their varnish on a wood fire, and then double attention must be given to prevent the drugs igniting.
“Melt all these drugs in the pot and stir them with a spatula so that they mix together and do not stick to the bottom. When they are well melted, pour in seven pints of linseed oil and mix it with the drugs, using the spatula. Cook the whole, stirring it from time to time to prevent as much as possible a kind of sediment which forms and does not mix with the oil from sticking to the bottom of the vessel. When the varnish is cooked, pass it through a cloth or strainer.
“This quantity of varnish should, according to workmen, remain seven to eight hours on the fire to cook, but this cannot be regarded as an invariable rule. It will not take so long to cook on a large fire. A better test used by workmen in manufacturing varnish is to take a few drops of the liquid with the spatula and lay it over silver leaf on some leather; or else they take some of the varnish in a silver spoon and, by trying it with the finger tip as if it were syrup, find out if it is cooked enough. If it ropes in cooling, or if the finger has a tendency to stick when it is gently withdrawn, it is a sign that it is sufficiently cooked, that is to say that it has arrived at the consistency of a thickish syrup. The varnish is then brown in colour, and curiously enough when laid over silver it becomes transparent and gives the effect of brilliant gold.”
While on the subject of gold groundwork made with gold or silver leaf or tin-foil covered with varnish to imitate the colour of gold, it is curious to note how far back in the history of art its origin can be traced; after the Greeks, the Byzantines made use of and, it may also be said, abused it. This want of moderation in the use of gold is to be met with long afterwards, for it is mentioned in his book on painting by L. Benedetto Alberti who died in Rome in 1472.[18]
[18] Sunt qui auro immodice utantur, quam aurum putent historiæ affere majestatem. L. B. Alberti, De Pictura, Book 2, page 25, ad finem Vitruv. Elzevir. f.
Van Orley, Raphael’s pupil, when painting his “Last
Judgment” at Antwerp, had his panel gilt in order to obtain “a beautiful transparency.”[19]
[19] Decamps. Vie des peintres flamands. Paris, 1753, 4 vols. Vol. 1, page 39.
We have quoted above the formula for golden varnish given by Fougeroux de Boudaroy which he ascribes to Réaumur. It may be found interesting to compare with it that given by the Monk Theophilus in his Diversarum Artium Schedula:—
“Put some linseed oil in a small new pot; add some gum arabic called fornis pounded very fine; this gum is like very light incense, but is more brilliant when broken up. Place it on a charcoal fire and cook it carefully without allowing it to boil, until it is reduced by one third. Be very careful of flames, for they are very dangerous, and the preparation is difficult to extinguish if it once catches fire. Any painting coated with this varnish becomes brilliant, beautiful and perfectly lasting....