You paint on a polish that looks creamy and opaque in the bottle, only to find it looks weak and translucent on your nails. And because you can rarely try polish before you buy it, you can't be sure of its sheerness until it dries into a negative-space manicure—that you didn't ask for. But there are creative ways to make your polish as rich and creamy as it looks in the bottle.
Manage your expectations: When it comes to nail polish, what you see is not necessarily what you are going to wind up with. When you condense nail polish in a bottle, it always appears more opaque. And keep in mind that nail polish's shelf life is a year, two at most. The older a polish gets, the more prone it is to chip, fade, and lose viscosity.
Ace your base: Using a tinted basecoat underneath your polish will make it appear more opaque. However, if three coats of polish provide the opacity you want, skip the basecoat. Your polish won't come out too thick since it's the same number of coats as a manicure that uses basecoat.
Just add flour: You can thicken your polish the same way you thicken your dough. Add a tiny bit of baking flour to polish that has become thin or watery. Start with very little and make sure you shake the bottle well. Be warned, if you add too much, you risk your nail polish becoming a chunky mess.
Layer it: If you are open to tweaking the color, paint a sheer shade over an opaque polish in the same color family or even over a complementary tone. It may even create a completely new look you can fall in love with more. If your sheered-out shade is on the dark side of the spectrum, use an opaque white nail polish as a basecoat. It will increase the opacity and brighten up the shade slightly. Just make sure to let the white polish dry completely to avoid streaks.
Multitask with a metallic: If you like the color but want more opacity, layer it over a metallic shade. This makes the color payoff more robust and gives the finish a bit of depth, like the gleam of a metallic Christmas ornament.
Mix it: If you are up for playing chemist, you might be interested in a combo nail polish. You can mix your sheer polish with an opaque neutral or a pure white lacquer to give it a bit more coverage. But add it slowly, drop by drop, and test it on your nails intermittently. There is the chance that if you introduce too much white into the nail polish, your polish will end up looking very white.