Leather upholstery gives car interiors a rich, stylish look as well as superior comfort. Unlike with cheaper materials, leather car seats can show indentations from heavy objects, keys or other items with sharp points. Leather repair and replacement can be costly, but many indentations can be removed at home through a combination of moisture, mild heat and conditioners. Isopropyl alcohol can be used to help eliminate tougher indentations.
Fill a clean pan or bucket with hot water from the tap. Get the water as hot as possible.
Soak a white washcloth or hand towel (or even a T-shirt) in the hot water.
Wring out the cloth about halfway, so that it is wet but not saturated, and lay it over the indentation.
Roll the tennis ball or basketball over the cloth to stretch the leather fibres, which will shrink back to their original length when they dry. For smaller, pronounced indentations, press on the cloth over the indentation with the backside of a metal spoon.
Remove and examine the upholstery. The indentation should appear less visible, although the leather might have "pruned" somewhat like fingers after swimming. This will come out as the leather cools.
Allow the upholstery to dry and repeat the above steps a maximum of three times.
Mix a 3-to-1 solution of isopropyl alcohol and water. The alcohol helps the water to penetrate and to evaporate.
Soak the washcloth or towel in your alcohol/water solution and repeat steps 3 and 4 above. Allow the leather to dry.
Apply a quality leather conditioner. Alcohol will leave the leather stiff and dry. Look for a conditioner with lanolin, not one that boasts mink or neat's-foot oil---these are not suitable for the coated leather used in auto upholstery.
Automotive upholstery is invariably a surface-coated (painted) leather. Penetrating it to reach the dented surface below requires moist heat or alcohol. Both methods above remove the surface protectants, which is why you must restore them with a leather conditioner or leather protectant. If the indentation is nearly but not absolutely removed, give it time; it should work out with use.
Do not take a clothes iron or hair dryer to your leather interior. You risk causing the leather to shrink and pucker, which will look far worse than the indentation.