Cleaning Hard Rubber

Hard rubber was a commonly used material on older landline telegraph instruments. Examples include key knobs, circuit closer knobs, sounder coil covers, and in some cases, telegraph key bases. Often these parts have dirt or other residue that needs to be removed.

Cleaning these parts is quite easy. You can wipe them with a piece of paper towel soaked in water with a bit of soap. Then rinse off and let dry. After the parts are dry, use a tissue to wipe on a tiny bit of mineral oil to restore the gloss to the parts so they don't look dried-out.

DO NOT use any cleaners like Windex on the parts. Although it will remove the dirt and make the parts look very clean, the ammonia compounds in the Windex will cause small white spots to form on the surface of the rubber after a period of several months. These spots are hard, crystalline deposits which make the surface feel rough. Examples of such spots can be seen below:



You might need to lightly buff the rubber with some 0000 gauge steel wool to remove the white spots. Then repeat the above procedure for cleaning the rubber. Remember to apply a tiny bit of mineral oil to restore the gloss.