Oil paint considered drying, those with an iodine number of 115-130 are semi-drying, and those with an iodine number of less than 115 are non-drying. Linseed oil, the most prevalent vehicle for artists' oil paints, is a drying oil. When exposed to air, oils do not undergo the same evaporative process that water does. Instead, they polymerize into a dry semisolid. This rate of process can be very slow, depending on the oil. The advantage of the slow-drying quality of oil paint is that an artist can develop a painting gradually. Earlier media such as egg tempera dried quickly, which prevented the
Narva Oil Plant from the power plants and the separate subsidiary of Eesti Energia was established. The retorting plant consists of two modified Galoter type solid heat carrier retorts (Enefit retort)—both processing 125 tonnes per hour of oil shale. Main products are fuel grade shale oil, raw material for bitumen and antiseptics. The designed annual capacity of the plant is 220,000 tons of shale oil and 60 million cubic meters of retort gas. In May 2009, Eesti Energia announced that it plans to build a new shale oil plant adjacent to the existing plant with processing capacity of 2.26 million tonnes of oil