The glues are the basic binders that hold together the structure of the guitars and determine their quality, robustness and acoustics. In my instruments, each element is bonded with the most suitable glue; adhesive resins are applied on the basis of their chemical characteristics, depending on the material to be bonded and the function that they have to play.
Glues I use are:
Aliphatic: is a non-toxic resin similar in appearance to the vinilic glue, especially suited to bonding porous woods. It is non-reversible, tenacious and highly resistant to solvents, paints and grease. Used in violin and cabinet making for several decades, it is now commonly used for all kinds of bonding and in the production of fillers.
Hide glue: is the most commonly used glue in luthiery thanks to its characteristics of practicality and reversibility. It is natural, non-toxic, water soluble and thermo-sensitive; its durability is proven by centuries of use in the construction of musical instruments. Above all, it facilitates best the propagation of sound. It can also be applied to wood as primer.
Cyanoacrylate: is an instantaneous contact adhesive particularly suitable for glueing different materials with non-porous surfaces. Given its ability to bind with biological tissues, it has been successfully used in surgical operations. It is waterproof and highly insulating.
Epoxy: extremely strong two-component resin. It is waterproof, insulating and heat resistant. Particularly suitable for bonding oily woods like cocobolo or olive wood, it can also be used as a primer, sealer or for the production of fillers.
The finish on a guitar is also very important, and mainly serves two purposes: one acoustic, and the other protective. It at once enrichens the harmonics of the guitar, and protects the wood from knocks, skin acid and sunlight.
Two types of finish are available:
Shellac: oleoresin, secreted by the female lac bug, on trees in the forests of India and Thailand. It is processed and dissolved in ethanol. Always applied by the “french polish” technique for finishing guitars, it gives the wood a natural and high-gloss look. Lightweight, elastic and very thin, the shellac layer is insulating and breathable at the same time.
Nitrocellulose: nitric acid-based, highly refined varnish of vegetable origin. Hard and very bright, the nitrocellulose is highly protective; it has been used in guitar making for about 60 years, and its chemical formula has been adapted over time to improve its acoustic performance. It can be applied by airbrush or hand-brush.