Making Sun-Thickened Linseed Oil.
Spring is here, time to make a new batch of sun thickened oil - a very useful medium for plein air
painting - when used in small amounts in painting media acts as a siccative drier.
Using a purified cold
pressed, linseed oil, pour the oil into a
shallow plate (about 5mm deep), then this needs to be covered with a
sheet of glass to keep dust
out . The process works by oxidation so
the glass needs to be raised somehow to allow air in. Put on a sunny
windowsill, the more sun it gets the
better. Air on the surface of the oil
and ultraviolet rays from the sun start a slow drying and thickening
process. It is important to remember to stir the oil every day to
prevent a skin forming. After two or three weeks the oil will be thicker
and more viscous. Decant into an appropriate air tight storage bottle
This
is a great medium for plein air
painting as it is half oxidized so dries quickly allowing
the painting to be worked on in thicker layers without it getting too
oily and slippery. The oil yellows slightly in the process and dries
with some
shine. As with all new medium, it
needs a little practice to understand its properties, and the viscous
flow should be adjusted by adding turpentine, (or Zest-it!) to suit your painting process. ( a recipe from "The Materials of the Artist" by Max Doerner. - quote: Cennini calls it the best of all oils "I could not give you anything better")
