another good trick is a dry paper towelFor a quick after-smoke cleaning after the bowl and airway is scooped, pipe cleaner cleaned and clear, and before a brisk buffing with a stiff and then a soft cloth, I like to clean off the bit on Vulcanite pipes with a bristle pipe cleaner to brighten it up. This isn't a strong measure, but keeps the oxidation at bay.
Olive oil could possibly go rancid.Immediately after each smoke I will thoroughly dry the stem. After the pipe has cooled down a bit, I give it a thin coat of olive oil and that's it. I have no reason to prefer olive over mineral but I do.
Mineral Oil is way cheaper than mineral oil with black die and possibly some UV blockers, and available at your Chemist's, Drug Store, Hardware store, maybe even gas station.
I'd first just rub the stem down with just a drop or two of mineral oil, see how they look. They may pass your inspection. Other more rigorous treatment can then happen if they aren't shiny or black enough for you.
Please post photos!
Olive oil could possibly go rancid.
I heard the stories but mine never did, for some reason. Maybe people are using unfiltered olive oil?
Any olive oil will go rancid in time. But on a pipe stem, the handling, cleaning, probably prevents that.
So-Called Obsidian oil is supposed to contain secret ingredients which effectively protects pipestems from harmful UV rays