Colophony cooked for 4,5 hours at 150 - 180 C
The temperature is gradually raised to keep the same viscosity
Weight reduction ~15%, mostly in the first 1,5 hours
Lots of stirring!! especially in the first hour when it fumes a lot
Linseed oil heated to the same temperature and slowly stirred into the colophony
Cooked for 15 min together with the colophony
Reducing temperature to ~100 C
Mastic drops added slowly while stirring
Cooked for another 15 min at lower temperature 90 - 100 C until foaming stops and the varnish is very calm
Balsam turpentine heated to simmer
Slowly stirred into the varnish and cooked 5 - 10 min until calm again
Filtered and decanted into a glass jar
Colophony 81 g -> 68,5 g
Linseed oil 69 g
Mastic 18 g
Balsam turp 35 g