Manila copal and colophony rosin esterification

The rosins cooking process and the preparation of the oil varnish

One of the oil varnishes I use for my instruments, is made with copal and colophony.

The esterification process takes about five hours, during which the resins are cooked at a high-temperature in an aluminum pot. The glycerol is added in small percentage, during the first step of the process. After cooking, the molten mass is poured into a flat container, to trigger rapid cooling.

The varnish preparation is now relatively simple. The esterified resin flakes are heated again for a couple of hours at 200°C with linseed oil, previously washed, oxygenated in the sun and then cooked.

The result is a beautiful amber-red colour varnish, of medium hardness, and with excellent adhesion and drying properties.