the name does indeed come from the HP book. About 6 years ago, when the formula was worked out, Kevin Sandes [Mayadigger] asked to try some of the 'magic' coin cleaner, as it does
work very well on most clay forms, and the name was born.
It is a homemade sodium sesquicarbonate, as the lab grade is harder to obtain, and who need 50 pounds. The formula for the most
part has been published here for several years, so no big secret, but again, most people don't want to deal with 5 pounds of materials for a limited purpose.
BD is spread by the dust, but it also needs humidity. This has been seen by me, and is also noted in the paper from the University of Texas, so it is not a limited observation. Most coins require a brushing after cleaning of any kind, I prefer a battery powered dremel with a
brass brush. It removes remaining surface oxides and in effect polishes the surface without grinding to bare metal. Many coins have a
fair percentage of iron in the alloys, there is a link to an
Italian paper buried in Forums archives that has a study of the metallurgy of a series of coins, that would account for the rust.
http://www.uniroma2.it/eventi/monete/nocpan.html , this was originally posted by Rugser many years ago.
Bruce