Here's a quick way to remove solids from used frying oil.
A downside to deep frying is the large quantity of oil that's often required. But unless that oil smoked or you used it to fry fish, it's fine to reuse it once you strain it. Our usual method is to pour the oil through a fine-mesh strainer lined with a coffee filter, which can take hours. We found a speedier way: Add cornstarch to the oil, which attracts and traps solids for easy removal.
Here's how to do it: For every cup of frying oil, whisk together ¼ cup water and 1 tablespoon cornstarch. Add mixture to warm or cooled oil. Heat oil gently over low heat (do not let it simmer), stirring constantly with heatproof spatula, until starch mixture begins to solidify, 10 to 12 minutes. Remove oil from heat and strain through fine-mesh strainer (or use slotted spoon to fish out gelled mixture). Don't worry if oil appears cloudy; it will clear up once reheated. Refrigerate oil and reuse up to 3 times.