The main ingredient in nail polish is a
chemical called nitrocellulose, which is
the material that coats your nails. Another
ingredient in the bottle is meant to keep the
nitrocellulose liquid before you put it on your
nails. This ingredient is called a solvent,
and the nitrocellulose is dissolved in it, like
salt dissolved in water. When you apply the polish
to your nails, the solvent evaporates away,
leaving the nitrocellulose dried on your nail.
Vegetable oil is the opposite of a
solvent for the nitrocellulose. Nitrocellulose
really doesn’t like to be dissolved in vegetable
oil. But, the solvent that the nitrocellulose is
dissolved in does like the vegetable oil. So,
when you add oil and mix, the solvent mixes
with the oil, and the nitrocellulose clumps
together and forms the slime that you see.
You could make slime by adding any oil to nail
polish, including olive oil, or peanut oil. Try it
and see if the slime you form is different!