You can get fingernail polish off carpet by applying either dry-cleaning fluid or nail polish remover. To ensure that this is safe for your particular carpet, test the product on a hidden area first.
Another method is to combine 1/4 cup hydrogen peroxide with 1 tablespoon of ammonia. Dab it on with a towel until the area is saturated. Then, take a piece of plastic wrap and put it down on the spot and cover with a stack of heavy books. Let sit overnight. Rinse well in the morning.
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