It has been recently discovered at Cambridge University that the instruments of Stradivari, Guarneri, Amati and other great masters, were covered with a layer of siliceous material, possibly pozzalana, bound together with a varnish-like material. This layer is permanent, and remains , softer, varnish proper has worn off. This is the famous "golden ground" seen on Cremonese master instruments. It is transparent, and deeply enhances the appearance, and reflectivity of the wood; but its most remarkable property is its effect on the tone of the instruments it covers. The sound is both beautiful and penetrating, and will fill a concert hall.
The ground used on all PAG instruments is very similar in composition and construction to these old grounds, with similar visual and acoustic results. It is also permanent. If the outer varnish is removed, the ground remains as fresh looking as when it was applied, with its beautiful reflections and golden color. It is instructive to see an instrument in this state, without the outer varnish hiding to some extent the aliveness of this ground.
The old master varnish, or varnish proper, on Old Italian instruments varies, but in most cases consists of a resin, or resins, in oil. There are many recorded "recipes" for making such varnishes from the fourteenth century onwards right through and past the Classical period of instrument making. Analysis of some of the classical makers' varnish using modern techniques confirm that this type of varnish is what was used on the Classical instruments. We cannot determine however, the exact recipe and techniques used to make and to apply these varnishes. Indeed, they vary from one maker to the next, and from one period to another of the same master. It seems that even Stradivari was continually experimenting.
The colours vary from light orange to deep red. Some of the color is partly the result of fading, or of darkening, with age; and some of it, the result of centuries of polishing. The main coloring matter is almost certainly madder lakes. They came into Italy around the time of the making of the great Cremonese instruments, and red itself was the color that denoted luxury and affluence. Consequently, the best instruments were red. Madder precipitated with alum makes the most lovely reds, and in oil varnish is transparent.
The old masters varnish used on PAG violins follows the same precepts, in consisting of resin(s) in oil, made according to the old recipes, which are basically very simple, if smelly, to do. Currently, I am using a varnish consisting of amber in oil. The madder lakes are made in the workshop directly from madder root, and can produce the most beautiful deep reds, as well as the lighter shades. The lakes are simply ground into the varnish, immediately before application to the instrument. The resulting finish on the instrument is a beautiful, transparent and lively varnish with golden underlays, and is as close to old master finishes as can be done.