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
Narva Oil Plant shale per year. It would produce 290,000 tonnes of shale oil and 75 million cubic meters of oil shale gas per year. The cost of the new oil plant is approximately 3 billion Estonian kroons (€191.7 million, US$264.2 million). The construction was launched in the second half of 2009, and the new Enefit280 plant was commissioned in 2012. The first barrel of shale oil was produced in the new plant on 20 December 2012. Narva Oil Plant Narva Oil Plant (), a subsidiary of Eesti Energia, is a producer of shale oil from oil shale. It operates a commercial scale