Adhesives

Praise the LORD with the harp; Make melody to Him with an instrument of ten strings. Sing to Him a new song; Play skilfully with a shout of joy. For the word of the LORD is right, And all His work is done in truth. He loves righteousness and justice; The earth is full of the goodness of the LORD. By the word of the LORD the heavens were made, And all the host of them by the breath of His mouth. He gathers the waters of the sea together as a heap; He lays up the deep in storehouses. Let all the earth fear the LORD; Let all the inhabitants of the world stand in awe of Him. For He spoke, and it was done; He commanded, and it stood fast.

Adhesives

Before we glue any joints it would be a good idea to take a quick look at the different types of glues that are available for the luthier.

In the construction of acoustic guitars there are no screws or nails or other mechanical fixings to fasten parts together so the joints must fit exactly, hence the requirement for top quality tools and the correct use of adhesives. The type of joint dictates the type of adhesive used. Some joints need to be permanent while others need to be non-permanent, for instance the joint between the bridge and the soundboard, the neck and fret board and in the case of the removable neck to body joint all need to be non permanent to enable repair work to be undertaken.

On these types of joints I use hide glue as it is extremely strong yet under local heat and moisture the joint can be undone without seriously damaging the wood.

On all other structural joints traditionally I used Cascamite (Urea Formaldehyde) which has now been renamed Extramite next year Vegemite? (Only kidding). The more restoration and repair work that I do using traditional hide glue makes me wonder why not use it exclusively on all joints.

I have used PVA glues to attach non-structural items such as purfling and binding strips. PVA glues can create a non-visible stain on bare wood that does not show up till the finish is applied. Additionally it does not sand very well, it tends to ball up and clog the paper. So I will experiment with Titebond, which is an aliphatic glue, with the idea to eventually use hide glue.

Traditional hide glue is made from boiling down animal hides such as cowhides left over in the meat industry. The glue is available in various weights (strengths), and the glue purchased from the shop normally in pearl bead shape is fine for most work. When the joint is properly prepared and the glue is at the correct temperature the glue will set up in the fibres of the wood giving a permanent final adhesion stronger than the wood itself. The only perceived disadvantage in using hide glue is that it takes time to prepare and is messy (ever watched a small child with a chocolate bar). This is not really a disadvantage as the art of making, repairing and restoring musical instruments is a creative endeavour. This then requires time, patience and the proper preparation of both the work on hand and the mind of the worker.

I use Cynoacrylate superglue to fix abalone inlay, as it's greatest benefits are its low viscosity and rapid set. I also use it when gluing the binding strips around the outer edge of the body.