I recently scored a pair of slide rules on eBay for not a whole lot of money. One was in excellent condition, but the other one has what the seller describes as “caked-up dust” on several placed, especially under the cursor. It appears to have been smeared down several of the scales. It’s more dirt than dust, in my opinion. In places I’ve lightly scratched it off with a fingernail and it’s come off, but the problem is too widespread for me to want to do that unless I have to.
My question is twofold: What the heck is a slide rule made of, anyway? And what’s the best way to clean a slide rule with the least possibility of damaging the scales?
For bonus points, can I easily remove the cursor to clean under it, too?
I’ve sold a few slide rules on eBay. Most are plastic or metal (aluminum) and few older ones are painted wood. The main issue for the plastic and metal ones is not damage to the underlying material but damage to the painted or anodized lettering. Also some plastic viewing bezels on less expensive models are made of a clear plastic that does not react well to alcohol based cleaners. A Q-tip and warm soapy water is generally the safest way to go. For non-painted & non-clear plastic areas alcohol is generally safe to use for stubborn grime.
Wooden painted rules are quite delicate and beyond my experience re cleaning.