to preserve them between painting sessions, usually suggested as placing your entire palette in the freezer, in based on the fact that oil freezes are a very low temperature. (It's far lower than water.) Given the temperature a domestic freezer is usually set at, leftover oil paint put into it is unlikely to freeze because it doesn't get cold enough.
I put the question to about freezing oil paint to Anne Marie Helmenstine PhD, About.com's Guide to Chemistry, who said: "The freezing point of linseed oil (the predominant oil in oil paints) is -20°C (-4°F). Most people set their freezers at 0°F, so oil paint will not freeze in most home freezers.
