VARNISH OF KRUTZ INSTRUMENTS
by Anton Krutz
Like most luthiers I have experimented for years with different grounds and varnishes. I've accidentally had cooking resins explode, blown a hole in my wall, caught my leg on fire, and that's just the tip of the iceberg. All in the name of finding "The Great Look!"
For those not familiar with the term "ground"; it is the sealer that goes on top of the bare wood before the varnish is applied. As far as I am concerned, it is the most important variable in the finishing process. The ground is actually what gives varnish its luster, beauty, and a look of depth, as well as improving the sound of the instrument itself.
The ground achieves this by a multi-process application: First, I apply an organic layer, which colors the wood, giving it a golden brown refractive sheen. Second, I seal it with a clear (fresco painters) casein. This is what hardens the outer surface of the wood, makes it impermeable to moisture, and most importantly gives it a coat uniformity.
For example, imagine a mattress with individual coil springs. Those springs are like the cells in wood. If you lay down on the springs without having a one piece spring net on top connecting all of them, then you will only strongly compress the springs you're laying on. But, if that spring net was there, then your weight or force you were exerting would to an extent, be distributed among all the springs. The same concept applies to instrument plates, especially the top plate. Each note causes different sections of the plate to vibrate, so the casein film helps distribute those vibrations to the whole plate. Improper grounds are why many instruments do not improve and even wear out with time, especially the factory made ones which usually have no ground at all. Last, I apply a layer of fused amber on top of a fresco layer of lime. This accentuates the figure in the wood and adds dichroism, which is the bending of light as it enters (the ground in this case) and is refracted out.
The emphasis of most books and topics of discussion is on varnish though. Its function is to protect the instrument, provide a colored transparent film to accentuate the ground, and not be constrictive to the plates' vibrations. The latter of its functions eliminates all spirit and lac varnishes. Those varnishes are as restrictive as a tight trench coat around an athlete.
That leaves oil varnish. The oil varnish I use now is a simple one of fused amber and sun-thickened linseed oil. Several lightfast (primary colors of) red and blue pigments and lakes are used for richness of final color. But there are tons of recipes and I sure feel like I tried a lot of them.
When I first started experimenting, the goal was to make the varnish rather than the ground have the refraction and dichroism, through chemical reactions etc. Since most of the authors were convinced the answers to "The Great Look" lay in the varnish, all kinds of exotic procedures were found to torture the varnish and its prosecutor as well. Many of the procedures were tedious, time consuming, and inconsistent. One time after five hours of preparation I overcooked some varnish by two minutes. It turned into unliquifiable solid mass.
INSANE! Its ironic how even after five hundred years of instrument making and countless volumes of written material on the subject, luthiers are still experimenting. Looking at other professions one can see standards that are followed. If a better process is discovered and proven to be effective, it then becomes the standard. Not so in violinmaking. Every luthier has their own personal varnish war stories and secret victory recipes.