You will need:
Chios mastic
alcohol 96%
glass jar with lid
nylon stocking
alcohol to clean equipment and brushes
Put 3 parts alcohol in the glass jar and add 1 part mastic tied in the nylon stocking. Suspend the stocking in the alcohol. The varnish will dissolve in about 3 to 5 days. The stocking can be discarded. Impurities, if any, remain in the stocking. The varnish is now ready for use.
The varnish blushes white in a humid atmosphere. Mastic is a natural resin, tapped from a small shrub that grows on the island of Chios off the Greek coast.