Prime examples

Before varnishing their instruments, most luthiers like to add a layer of primer to the wood. Vlado Tilev shares his observations on the different types available, and their effect on sound quality

Primer and varnish ingredients in Vlado Tilev’s workshop

The primer under an instrument’s varnish has been a matter of concern to the makers of stringed instruments for decades, even hundreds of years. The mysteries of its composition and application have intrigued luthiers right up to the present day. I would like to share the observations I have made during my time as an instrument maker, focusing on several types of primer and their impact on the appearance and the sound of instruments.

It is generally considered that any penetration of varnish into the wood of an instrument leads to poor sound results and a mediocre visual appearance. There may be opposing opinions but for me, the necessity of an insulator (a primer) that prevents varnish penetration is unquestionable. Primers can be divided into two types based on their composition: oil-based and water/ protein-based primers.

For oil-based primers, either coldpressed linseed oil or linseed stand oil are commonly used as the base. This is where I must stress that working with cold-pressed linseed oil requires a great deal of care and attention, as it dries quite slowly and can easily penetrate deeply into the wood, which leads to a negative effect on the instrument’s sound. Therefore it is essential to apply it to the surface of the instrument using a lightly oiled cloth, to achieve a very light coating of oil on the surface of the instrument plates.

IN GENERAL, THE SOUND OF INSTRUMENTS IS INFLUENCED BY THE PRIMER

After applying the oil, it is necessary to expose the instrument to moderate sunlight to activate the drying process. If the weather does not permit the use of sunlight, an ultraviolet camera is required. It is worth mentioning that the lamps used should not be very strong, as this could lead to two potential problems: it could cause the wood to crack, and excessive UV rays can lead to a loss of elasticity in the wood and less vibration in the boards, which logically leads to a loss of sound. (The humidity in the box should also be taken into account; I am also very cautious about the power of UV radiation, as it is well known that excessive exposure to UV rays is harmful to human health.) From a visual perspective, the wooden material treated with cold-pressed linseed oil yields excellent results, significantly emphasising the depth and pattern of the wood.

Linseed stand oil (thermally treated linseed oil) has the advantage of drying faster than cold-pressed linseed oil, but it is much thicker and requires more skill in application. From my experience, I can say that an excessively thick layer of linseed stand oil does not have a good effect on the sound of the instrument. Its visual effect, though, is even better than that of cold-pressed linseed oil, if applied thinly and evenly. In general, the sound of instruments is influenced by the primer, and I dare say that oil grounds add softness and elegance to the tone.

Let’s now turn our attention to the protein–water primers. The use of egg white as a base is very common, as it shows up the wood very clearly. It is applied thinly, but the downside is that this base is relatively soft and not very durable. It gives a more direct timbre to the instrument, with a softer sound. The other option for a primer is to use a mixture of hide glue water and a little bit of alum. Prepared this way, the base is very durable and almost waterproof after the mixture has fully dried. Instruments primed with this base have a sharper timbre, but also has great penetration. Even though I would not compare the visual effect of the hide glue water to that of the oil varnish, it does have its advantages, depending on the wood used for the instrument.

Cold-pressed linseed oil primer

ALL PHOTOS VLADO TILEV

Casein-based primer

Hide glue water/alum mixture

The third option for a water-based protein primer that I will discuss here is the casein-based primer. This is known for its great strength and, when mixed with alum, it leads to high water resistance. However, this base has high transparency, which does not give enough depth to the pattern of the wood. It does not create the 3D illusion that is observed when using an oil-based primer such as cold-pressed linseed oil or linseed stand oil. It should also not be applied excessively, as a thicker layer may cause cracking, which leads to visually poor results. Regarding the sound, I can say from my observations that the caseinbased primer contributes to greater power and penetration. But if you are looking for a softer and more beautiful timbre, then your insulator ought to be oil-based.

IN SACCONI’S VIEW, APPLYING THE ‘BIANCA’ VARNISH LEADS TO A SIGNIFICANT CHANGE IN THE SOUND

I should add that each primer should be selected based on the qualities of the wood you are working with. The softer the wood, the stronger and harder the primer should be, and vice versa.

As a final option for primer, I would like to reference the opinion of the renowned Italian luthier Simone Fernando Sacconi, which is mentioned in his book The ‘Secrets’ of Stradivari. He writes about the so-called ‘Bianca’ varnish, which is a mixture of water, sugar, egg white and gum arabic. (The proportions of these ingredients are of personal choice for each individual maker.) Applying this mixture to the surface of the instrument leads to a significant change in its sound. I would recommend using it if the wood you are working with is very soft, because when the mixture dries on the wood surface, it significantly hardens it. No particular visual effect is observed, but the effect on its sound can be very good, if you are working with the appropriate kind of soft wood.