Violin Making: Preparing the Violin Plate Before Varnishing
The purpose of pre-treating the violin plate before varnishing is to achieve uniformity in both the internal and external surfaces, as well as throughout the wood material. Even when the wood is split during the crafting process to create the arching and thickness, some of the parallel wood fibers are severed.
Pre-treatment aims to homogenize the wood, restoring it to a cohesive whole. This homogenization leads to better vibration effects, crucial for the resonance of the violin, ensuring a sustained sound conducive to shifting positions and producing multiple string tones simultaneously.
The material used for pre-treatment should be waterproof and corrosion-resistant, impervious to both alcohol and oil-based varnishes. It should penetrate the wood to homogenize it, facilitating easier vibration and amplifying the amplitude. Even without a base coat of varnish, the violin's tone quality remains excellent. The material should have a glossy finish, enhancing the reflection of wood grain and patterns, thereby increasing the varnish's transparency and shimmer.
Additionally, it should adhere firmly to the wood, such that even if the varnish chips, it remains attached to the wood, ensuring the wood stays clean. Removing it should result in the material being removed along with the wood.
Linseed Oil
Applying linseed oil to the surface of a white violin before varnishing is an essential step. A single application of a sufficient amount of linseed oil ensures penetration into the wood, reaching the inner surface. Not only does this method provide excellent protection to the wood, but it also enhances the visibility of the grain and patterns, giving depth and beauty to the wood.
Moreover, linseed oil dries quite slowly, requiring 4-5 days for complete drying, allowing the oil to penetrate throughout the wood and seal it off, preventing the primer from penetrating. The elastic substance formed by the dried linseed oil within the wood seals the various components and organizational structures of the wood into a consistent and uniform violin plate, making the wood fibers coherent and elastic, facilitating easy vibration of the plate and reducing moisture absorption on the inner surface of the plate.
After treatment with linseed oil, the violin becomes lighter because the oil displaces the moisture within the wood, and the density of oil is less than that of water. To facilitate the drying of linseed oil, gentle heating and exposure to light are required. However, light exposure only affects the outer layer of oil, while heating affects the oil absorbed into the wood. The temperature applied should not exceed the temperature of sunlight (155 degrees Fahrenheit, 68.3 degrees Celsius). Heating should be done continuously to prevent oil droplets from seeping out. UV irradiation may be used as an aid during heating. Linseed oil, after such drying treatment and oxidation, no longer dissolves in turpentine or alcohol. Modern German violins still use linseed oil for pre-treatment.
Egg White
Whisk fresh egg whites until frothy, then extract the thin liquid. Add a few drops of a 2.5% solution of gum Arabic, along with a small amount of granulated sugar and honey. Stir well and use immediately. Honey adds elasticity but excessive amounts can cause stickiness, while sugar acts as an antioxidant to protect the wood.
The egg white and gum seal the micro-pores on the wood surface and gaps between fibers, ensuring even coloring during priming and preventing paint from penetrating the wood during base coating. To ensure uniformity of the inner and outer surfaces of the violin plate, brush the mixture onto the inner surfaces of the plate, ribs, linings, and corner blocks 2-3 times before gluing the panels together. Apply thinly and evenly to avoid forming a thick film, as it may affect plate vibration.
Wipe off excess egg white after the third application. Before varnishing the assembled violin, apply the same treatment to the outer surface of the body. Once dried, the egg white hardens and becomes completely transparent, homogenizing the plate and preventing further moisture absorption.
Gelatin
Apply a 5% gelatin solution to the wood surface, similar to the traditional priming method. It effectively prevents uneven pigment absorption and primer penetration. If formaldehyde is brushed on after applying the gelatin, the gelatin will solidify and seal the pores on the surface of the plate, reducing the impact of moisture. However, since a water-based solution is used, it may have negative effects on the violin, so some people may prefer not to use it.
Gum Arabic
Gum Arabic, commonly used for priming, is a water-alcohol solution made from gamboge or resin. It serves both as a coloring and adhesive agent, allowing for a single application.
Silk Glue
Silk glue is the adhesive found between the silk threads in silkworm cocoons. To extract silk glue, cocoons are split open, and the pupae are removed. The silk cocoons are then soaked in hot water to allow them to swell, causing the silk glue to dissolve into the water. After concentration, a silk glue solution is obtained.
In ancient times, it was used to protect paper and documents. When dried, silk glue leaves a translucent yellow film on the paper, which prevents insect damage because pests do not eat silk. It also provides waterproofing and preservation properties. Using silk glue to pre-treat the wood of violins has similar effects, preventing uneven coloring and primer penetration into the wood.
Water Glass
Modern industrial water glass is a solution of potassium silicate and sodium silicate. Potassium silicate, being less alkaline, is more suitable, and it tends to have a green-yellow coloration, giving it a cool tone.
In ancient times, water glass was made by processing grape vines and ash into wood ash, along with quartz powder and carbon powder. However, modern industrial products are not suitable for this purpose. Generally, it is not used on new violins, but if the violin plate is too thin during repairs, several layers of diluted solution can be applied to the inner surface to increase the plate's hardness.
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