Violin making is an art form. Scientists have even studied a famous type of violin called a Stradivari (made by Antonio Stradivari, one of the world's greatest violin makers), attempting to analyse the various components making up the violin to discover why one instrument may sound more beautiful than another. Likewise, violin makers have experimented for years with grounds, varnishes, and colours in order to create an instrument to look as stunning as it sounds. After the wood carving and the gluing of the violin parts is completed and the violin has been exposed to the air and to UV light for several weeks, violin makers must then apply first a ground coat and then a varnish.
The first step to preparing the violin's finish is a ground coat, which is a primer or sealer, just like painters use primer. You can make a ground coat from a variety of different materials such as turpentine, terpene resin, linseed oil, or propolis soap. When you apply a ground coat, it works to help protect the wood as the varnish wears away with time and use. Some also believe that the ground coat is the largest contributing factor to the sound of the violin because it hardens the wood, which inhibits the vibration of sound.
Resin/Oil Based Varnishes
After the ground coat has been completed, the varnish can be applied. Resin- or oil-based varnishes are two options. You can use natural or plant based materials to make a resin-based varnish, or "gum." Usually, you also mix in linseed or walnut was well. You cook and then thin the materials with turpentine to create a liquid varnish which you apply in two coats. You can use a variety of recipes and techniques to create the perfect varnish. Most violin makers practice and refine their particular recipe until it produces the desired results. In fact, many guard it as a trade secret.
Spirit or Alcohol Based Varnishes
A spirit- or alcohol-based varnish is an alternative to a resin varnish, also applied after the ground coat. Shellac is the most common spirit varnish and is a single component resin which is alcohol soluble. It comes from the Coccus Lacca insect, and is harvested from tree bark in Assam and Thailand. It goes through a special process to be "de-waxed," producing a sheen that cannot be mimicked. Shellac varnish may be clear, or coloured with amber, orange, or red hues.
A colour coat may be added with any varnish to add even more depth, texture, and contrast. To create a colour coat, you mix finely ground lakes into the varnish or glaze them onto the surface between coats of varnish. Lakes are organic, plant-based materials made by precipitating natural pigments onto alum. The coloured lake particles help light to penetrate and maintain translucency, while at the same time refracting light to allow the varnish to appear as one homogeneous colour.