> I am doing a science fair project on which nail polish dries fastest. I am
> having trouble finding out which ingredient is responsible for this. The
> manufacturers claim it it top secret. Can you help me out. Thanks Megan

This can be done in two ways.

• Use a solvent with a low boiling point so that it will evaporate quickly. This is the simplest way of doing things and is most commonly used. I would be surprised if there are any nail polishes which use the second method; certainly all house paints and even industrial exterior paints dry by evaporation of the solvent.

• Use a solvent which will solidify (usually by polymerizing) on exposure to some outside agent (oxygen, UV light, electricity, another liquid with which it is mixed just before applying, ...) This is much trickier - you don't want your nail polish to harden before you apply it! - and tends to be used either in adhesives (super glue and epoxy cement, for example; the one dries on exposure to air, the other when you mix its two components) or under carefully controlled conditions in industry (GM, I think, still uses electricity to paint many of its car bodies before assembly).

It may be that someone has invented a way to make nail polish set on exposure to keratin (the protein in fingernails); if so, that would be pretty neat. But I doubt it. Quick-drying polish is most likely a function of

• quick-evaporating solvent and/or
• a combination of pigment and binder which gives a good coat without having to go on too thick (the thinner the coat, the faster the solvent can evaporate).

Incidentally, you may want to make sure you are controlling for film thickness when you do your tests; there are a number of ways to do this which are used in the coatings industry, and which I will be happy to explain if you contact me. My initial guess is that, if you control for thickness, you'll find that the polishes dry at about the same rate but some will "cover" better than others (they'll be less transparent).