Sadly most
bulk cleaning involves chemicals. There are a few large dealer (or middle-men) who apparently know what to do with large
scale chemical
baths and constant supervision. Supposedly
good results can be
had. But most such attempts, especially by those not "in the know", end in failure - just check out "uncleaned coins" on flea-bay to see the results.
I don't even know if this
type of
bulk treatment works for "desert
patina" coins. I have heard that some dealers have used manual labour for cleaning these - paying people in the Middle East where labour is much cheaper.
What are your coins for?
If for sale I would suggest
selling them uncleaned. I think there is a big market for uncleaned desert
patina coins in small lots. If for yourself then why
work on them individually. The methods posted by others here, including Salem, can
work effectively and quickly. All you are really doing is wetting the coin and rubbing sand/dirt off the highlights.
SC