To assess the quality of fresh fish and seafood, there are a few simple things to look for: Fresh whole fish should have bright, clear eyes; skin should be shiny, firm and elastic to the touch, gills should be red not brown, and if gutted, the cavity should be clean.o assess the quality of fresh fish and seafood, there are a few simple things to look for: Fresh whole fish should have bright, clear eyes; skin should be shiny, firm and elastic to the touch, gills should be red not brown, and if gutted, the cavity should be clean.
Drying oil. A drying oil is an oil that hardens to a tough, solid film after a period of exposure to air. The oil hardens through a chemical reaction in which the components crosslink (and hence, polymerize) by the action of oxygen (not through the evaporation of water or other solvents). Drying oils are a key component of oil paint and some varnishes.
Together with natural gas, it makes up petroleum, which is Latin for rock oil. Petroleum is basically a mix of naturally occurring organic compounds from within the earth that contain primarily hydrogen, carbon and oxygen. When petroleum comes straight out of the ground as a liquid it is called crude oil if dark and viscous, and condensate if clear and volatile. When solid it is asphalt, and when semi-solid it is tar. There is also natural gas, which can be associated with oil or found alone. Crude oil comes in many forms. Usually it is black, but green, red or brown oils are not uncommon. Thin and volatile oils are called light, whereas thick and viscous ones are heavy. Light oils have an API gravity of 30 to 40 degrees, which means that the density is much less than 1.0 g/cc.