Taking the first step

Making and applying the ground coat is a crucial stage of the varnishing process. James Ropp reveals his own method for a preparation containing no oil

MAKING MATTERS

Points of interest to violin and bow makers

Violin with a completed ground coat

The methods described in this article are the methods I use based on extensive research and experimentation. First, let’s discuss the purpose of the ground on the tonewood of an oil-varnished stringed instrument. Since I primarily make violins, I will use the violin as the example for this article.

The ground coat serves two basic purposes. First and foremost, it is a sealant forming a barrier between the cells of the tonewood and oils in the varnish. A violin’s tonewood produces its beautiful sound, with the tone being generated from the resonant vibrations of the tonewood’s cell structure. Any mass added to this cell structure, such as oil, will inhibit the way the tonewood resonates. A good analogy is the effect of a mute on the violin bridge on its tone and projection.

The second purpose of the ground is the aesthetic quality it provides. The finest examples of the beauty that a ground adds are the instruments made during the Cremonese ‘golden age’ of violin making.

There are many recipes for making a violin ground, and there are many off-the-shelf grounds that can be purchased. I have my own personal recipe that I developed after much trial and error. If you are thinking of formulating your own ground, here are the criteria I used.

First of all, select a medium that will bond with the wood and the varnish you will be using. This medium forms a thin layer on the tonewood and must not penetrate deeply into it. Some traditional recipes use mediums such as egg whites or gelatine, which work well as they are not soluble in oil, turpentine or alcohol. The medium I personally use contains no oils and is water-soluble.

I have found that adding a percentage of limestone can soften the tone of a violin slightly. You can experiment with varying amounts of powdered limestone or other minerals to vary the tone a little. Remember: any mass you add to the tonewood acts like a mute on a bridge.

ADDING A PERCENTAGE OF LIMESTONE CAN SOFTEN THE TONE OF A VIOLIN SLIGHTLY

Materials used in the preparation

Colouring your ground can be accomplished with modern dyes (such as analine dyes), or with traditional colourants. Here some of the most popular traditional colourants:

Saffron tincture. This is easily prepared and applied as a tincture to colour egg white. The colour quickly mellows from its initial intensity, then stabilises for several weeks. Take a generous pinch of saffron and turn it into powder using a mortar and pestle. Then add a small amount of water and strain it through a coffee filter.

King’s Yellow or Orpiment tincture. This is an arsenic colour, so using it is dangerous. It was once considered the best and brightest yellow available.

Mixing the ingredients

Testing out the mixture for colour

Quick working is necessary

Coating the scroll can have some tricky moments

ALL PHOTOS JAMES ROPP

Buckthorn bark tincture. This has a warmer but less brilliant yellow when compared to saffron.

Madder root. While it is reddish at full strength, it is yellower when diluted. Combined with saffron, it becomes a golden yellow. Note: madder root as a colourant will decay when subjected to intense light or sun.

Next, I mix small batches that will be enough for one or two violins. My favourite mixture comprises a quarter-cup of a water-based poly-acrylic enamel as a bonding agent, thinned with about 1/8th of a cup of distilled water. This creates an oil-proof barrier. I also add two or three drops of amber-yellow aniline dye, which will not fade when exposed to light. You can also use undiluted albumin, which is another of my favourites as a bonding agent. Casein or collagen dissolved in water to a semi-thick consistency can also be used as a bonding agent. If you use a modern aniline dye, two or three drops of an amber yellow will be sufficient. If you prefer using a natural colourant such as saffron, add as needed. Start with a small amount of colourant, and test on scrap tonewood until you get the colour and intensity you desire.

(A quick note on using albumin: this is made by whipping egg whites until they form peaks when the whisk or mixer is lifted. The whipped egg whites are then covered and put into the refrigerator overnight. The clear liquid at the bottom of the bowl is albumin, which can be used at full strength with the colourant and additives.)

Then you can apply the ground coat evenly to the violin plate with broad, even brush strokes. Work quickly as the mixture will dry very fast, and you should avoid overlapping areas where the ground has already dried.

Allow it to dry thoroughly before applying one or two more coats of the ground, lightly sanding with 1,000-grit sandpaper between coats. If saffron is used for the colourant, I prefer to use a UV lightbox to stabilise the colour and to help with darkening the tannins in the wood. A couple of days usually accomplishes this for me. Once the intensity and smoothness have been accomplished with your ground coats, then your varnish coats can be applied.

I have found that keeping any oils from penetrating the cell structure of the tonewood to be extremely important in producing an instrument with great tone and projection. With this in mind, I never handle the unfinished wood with my bare hands and always use protective gloves. My concern started about eight years ago from reading an article about the effects of oil infused into tonewoods. In the article, a well-made violin was left in the white. The instrument was played and the tone and projection noted. The research found that the more the violin was handled, the less projection it had and the tone also degraded. I have attempted to reference the article, but have not been able to locate it again.