The same cheap oil fills transformers, glosses Swedish Fish and ages poker chips
Mineral oil is a clear, odourless by-product of refining crude oil into petrol. Because it neither conducts electricity nor absorbs water and has almost no taste, it turns up in surprising places: inside power transformers, on wooden chopping boards, in baby lotion, in candy, and in a neutrino experiment.
The name has been used loosely since 1771 for many different oils, partly because merchants and buyers had no need to know the exact chemistry, which could not be analysed anyway before the late 19th century. Britain sells it under Latin labels such as paraffinum liquidum, often spotted on baby oil ingredients. Chemically it is mostly alkanes and cycloalkanes, a relative of petroleum jelly, and lubricant grades are called base oils.
Its electrical behaviour explains a lot. As transformer oil it insulates and cools, and in high-voltage switchgear it helps disperse arcs. Hobbyists immerse computer parts in it for cooling, and radio amateurs fill homemade dummy loads with cheap veterinary-grade oil. Since it cannot be compressed, it also serves as hydraulic fluid, and as brake fluid in some Citroëns and bicycle disc brakes. Chemists store lithium, sodium and potassium under it to keep them from reacting.
In the kitchen, rubbing it into wooden bowls and boards stops them soaking up liquids and cracking. Confectioners use it to make sweets shiny and stop them sticking together. In laboratories, a thin layer over tiny drops of culture medium keeps embryos in IVF dishes from drying out or suffering temperature shocks. Farmers swab it onto chickens' legs to smother scaly mites, and gardeners spray it to suffocate aphids.
Some uses are pure ingenuity. Soaking new clay poker chips gives them a worn feel instantly. Mechanics burn it to make thick white smoke that reveals leaks in a car's fuel vapour system. The World Health Organization treats barely processed grades as carcinogenic but highly refined ones as unclassifiable, and the oil's main drawback is that it breaks down poorly in nature.
Source: Mineral oil
