In addition to de-ghosting a bowl, I've discovered another valuable use for coffee grounds. While watching one of Briar Blues' YouTube video reviews of Peter Stokkebye Luxury Navy Flake, Mike Glukler starts by saying how tired he is after spending three hours cleaning pipe rims, then ticks off a few things restorers use, including " a damp cloth, coffee grinds, and various instruments of destruction".
As it happened, I was trying to figure out the best way to remove the lava (as opposed to simply tar) all around the rim of my recently acquired 1927 Dunhill Shell billiard. I didn't want to get it too wet, since the stain used for these pipes seems to be water-soluble. Hearing Mike's brief mention of coffee grinds sounded like it could be just the ticket.
I took a damp section of paper towel, folded over several times and placed it in a tiny, shallow, flat-bottomed bowl. On top of that paper towel, I placed a 1/4 to 1/2-inch deep layer of tamped grounds, damp from the brewer. The object was to provide a layer of damp grounds which remained in contact with the rim, but not much more, as I wanted to minimize the wet grounds contacting the sides of the bowl. I then placed the pipe bowl, rim down, onto the grounds, pressed down with modest pressure, and scrubbed the rim with the damp coffee. I scrubbed for a few minutes, periodically lifting the pipe to clear the grounds which crept into the bowl and rotating the pipe in my hand to ensure that I was scrubbing the rim evenly. This seemed to remove the bulk of the lava. I then grabbed a stiff toothbrush and gently scrubbed with a dry brush for a couple more minutes.
The rim now looks practically brand-new, with every nook and cranny cleared of lava. The stain was unaffected and it took very little effort. I'll be interested to try this method on a plateau or smooth rim. Next time, I might swap the paper towel for a thin cellulose sponge, as the paper started to tear toward the end of my scrubbing.