What’s your violin’s coat made of?
…and is Antonio Stradivari’s sound secret hidden in the varnish?
a Lorenzo Storioni model Viola d’Amore halfway through the varnish process.
When mentioning violins in this context, the same applies to violas, celli, double basses
and all other stringed musical instruments of the traditional folk and baroque period.Do check out my new blog post as well to compare cleaning and disinfecting methods for your instrument to safely surf the waves of the SARS-CoV-2.
Why varnish an instrument?
In short: to protect the wood underneath from any damage or atmospheric (room and humidity) changes.
Wood (especially the carved arches of the soft and straight lined spruce of the top plates) has open pores that make it easy for dirt to get into the wood. To stop this these pores should be sealed off to keep the instrument looking Varnish also adds depth to the look of the instrument, so it has to showcase the timber underneath. We do not want it to be too opaque, but we want enough colour to make an impressive statement with the wood, but stain the wood too dark and it looks stained (= bad).
We want the protective varnish to be strong, but malleable, but durable. It has to protect against water, humidity, dryness, UV-light, heat and cold and light knocks. The instrument has to have a bit of colour, but not be too transparent (underwhelming and light) or too opaque (no flame figure or growth rings visible). It has to be easy to apply, dry reasonably fast and not interfere with the sound too much (too many (thick) layers dampen the sound). I once had a wolf tone in one of my early newly handmade violins, which indicates the top plate is thinner in a few key places. I gave it two more oil coats, then gave the instrument a good and final polish (so effectively it had the thickness of one oil coat added) and the wolf tone was gone. Every coat of varnish you add to a violin has an effect on the sound. So finally… we want a little dampening, but not too much.
Producing a good varnish is not easy.
Also, violin necks are hardly ever varnished these days (like they were a few centuries ago), and they are more often just finished with oil to protect the wood now.
Exhibition display of some of my varnishes and pigments
which I commonly use in the colour coats of an instrument’s varnish or as retouching materials.
Traditional varnish is a mixture of natural resin (i.e. from pine sap and derivatives, copal, amber, sandarac, mastic, etc.) and a drying oil (i.e. like linseed, not olive oil) cooked at high temperatures for a long time. It is boiled down to evaporate any undesired traces to leave two pure ingredients that combine the durable hardness of the rosin with the ‘liquid’ plasticity of the oil. This creates a viscous sticky material that when cured makes a protective layer that is both durable, movable and enhances the visual pattern of the top grade timber underneath. Traditional oil varnish dries by oxidation and cures by polymerisation, (creating long chains of molecules that form a ‘net’ of “interlocking fingers” for strength). Many artisan makers still use the traditional recipes and techniques of old to create a timeless effect on their hand crafted instruments.
Modern day varnishes are (mostly) synthetic, or synthetic mixed with oil. There are three types of modern oil-based varnishes: Phenolic resin, Alkyd resin, and Polyurethane. The latter is never used on fine instruments but is indeed classified as an oil varnish. Most modern oil varnishes for mid- to high end manufactured violins (violas, celli and double basses) are alkyd varnishes (polyester resin cooked with oil) though some could be phenolic.
Synthetic lacquers (mostly nitro) are typically used on instruments like steel string guitars, almost never on violins unless it is for the starter level trade manufactured ones. These varnishes are used for economy as it’s a quick application (sometimes by spray paint) and it is a quick drying option to protect the wood underneath. ‘Nitro’-laquer gives a "glass-like" shine with lots of colour in not very many layers. Lacquer has been various things through history, but currently the term typically refers to evaporative drying or catalyst-curing finishes, usually sprayed, which are based on either nitrocellulose or acrylic resins. What the Chinese use on spray-finished violins is another question.
Then there is the lacquer known as ‘spirit varnish’. It is a combination of alcohol (= high percentage ethanol) and shellac – a waste product produced by the female lac bug (that is processed, purified and made into flakes).
The last option is French-polished (the technique) shellac. It is a nice hand-finished look on a guitar, a table or a door, but intensely difficult to do on a violin as it has so many tight corners, bends, nooks and crannies, so it is not commonly done. Almost all higher end classical guitars are French-polished. It leaves the thinnest surface possible, without any "glassy" look.
four college instruments from front to back: 1-spirit varnish, 2-opaque oil varnish, 3-antiqued stain no varnish yet, 4-’unpigmented varnish
Spirit varnish dries very quickly (c.a. 30 mins - 2 hours between coats) and it is the go-to varnish for retouching work. On the downside, because spirit varnish evaporates fast, it can also appear patchy or blotchy on the violin surface and brush strokes can be visible in the finished coats. Any shellac-based finish can be damaged by cleaning agents consisting of alcohol and/or water.
Oil varnish is generally more forgiving and takes longer to dry (2-3 days between coats, but depending on the drying conditions can take up to a week to dry per applied coat). It evens out and levels any marks like brush strokes automatically before the coat dries. However, because oil varnish takes longer to dry, it can be a problem in (high) dust areas as particles and fruit flies get stuck in the viscous material before it cures, which will need to be lightly evened out before the next coat goes on.
What about Stradivari’s secret sound, is it in the varnish?
Most of Antonio Stradivari’s instruments are in instrument collections in museums, private collections or in the hands of world class players. As some instruments are up to 350 years old, they have lived through the Bubonic plague and the Spanish influenza outbreaks and survived European wars too many to name. The instruments got damaged, repaired and polished up to upcoming and fading fashions. Generations of sweaty hands, chins and shoulders through lack of chin-rests, shoulder-rests, and sliding protective cases too added to the long lasting wear and tear of the varnish.
As a result of this, any original varnish left on the instruments would reside in some parts of the corners on front or back plates.
Though the wood has aged gracefully over time,
perhaps part of the secret of his instruments is that there is no original varnish left!