How do you remove dark oil stains in a concrete countertop that seem to have soaked into the surface? I've tried several types of cleaners, and nothing seems to work.

Oil stains can be especially difficult to remove because unlike most stains, which stay near the concrete's surface (or are only in the sealer itself), oil penetrates deeply into the concrete. Generally, removal requires the use of a strong poultice. Different people have different recipes and techniques for applying poultices, but they all have the same basic characteristics.

A good poultice for the removal of oil stains is a mixture of baking soda, powdered sugar, or flour with acetone, making a peanut-butter-like paste. The poultice is spread on the oil spot to a thickness of about ΒΌ inch, then covered with plastic wrap that's taped down to seal in the poultice.

Generally this mixture is left on for 24 hours to give the acetone enough time to work on the oil and make it easier for the absorbent material to draw the oil out of the concrete. After 24 hours have passed, the plastic is removed and the poultice is allowed to dry. This is when the oil is drawn out of the concrete, so patience here pays off. Stubborn oil stains can take multiple applications of poultice to completely remove.

Keep in mind that most sealers are vulnerable to acetone, so it's vital for you to verify before applying the poultice that it will not damage the sealer and remove the protective finish.

Mixing a poultice. Applying a poultice. Covering the poultice with plastic.

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