Oil paint very slowly, darken, and crack, unlike mastic and wax (the latter of which was used in encaustic painting). Greek writers such as Aetius Amidenus recorded recipes involving the use of oils for drying, such as walnut, poppy, hempseed, pine nut, castor, and linseed. When thickened, the oils became resinous and could be used as varnish to seal and protect paintings from water. Additionally, when yellow pigment was added to oil, it could be spread over tin foil as a less expensive alternative to gold leaf. Early Christian monks maintained these records and used the techniques in their own artworks. Theophilus
Oil production plant Sometimes the produced oil may be "stabilised" (a form of partial distillation) which reduces vapour pressure and sweetens "sour" crude oil by removal of hydrogen sulphide, thereby making the crude oil safer for storage and transport. The production plant is said to begin after the production wing valve on the oil well. The product from each well is piped through the choke valve, which regulates the rate of flow. The flowlines are gathered at the inlet manifold and routed into a separator, which will separate the three components. Once the oil has been separated from the gas and produced water,