How do you tell the difference between oil or acrylic based paint.?

Answer 1

The oil floats to the top in oil based paints after sitting unopened for a few weeks.

Latex based paints will also separate and will look watery at the top after sitting for a few weeks.

You can also read the labels on the cans - they should indicate what the base is made from.

Answer 2

The first and most obvious difference between acylic and oils is the drying time. Acrylics dry in a number of minutes- oils generally take upwards of a few days to dry, and a few weeks to completely dry. Thickness, too, is a difference; acylic out of the tube comparatively less viscous when compared to oil paints, which are "less wet" and usually require some kind of medium (Linseed oil traditionally, though Turpentine and other synthetic thinners are getting more and more popular as they are less of a fire hazard) when painting with it. Oil paintings tend to have more texture (i.e. more ridges and bumps in the paint) because of its high viscosity, while acrylic paintings generally feel more flat when you run your hand over them. In the long run, oils last for longer and their colors fade less over time than acrylics- thus their popularity in old paintings. This is just my opinion, but painting with oils allows you a lot more freedom- since the paint doesn't dry almost immediately as with acrylic, you can push the colors around on your canvas much more easier and blend much better. This quality of oil paints is what lends itself to being an excellent medium if you want ot paint photo-realistically. And lastly, the most definite way you can tell an if a painting is in oil paint is by the smell: oil paints smell terrible. (And also depending on the material the color, cancerous; the tube should tell you if its toxic though).