On Jul 21, 4:14 am, "Mr. Jaggers" lugburzman[at]yahoo[dot]com wrote:
"Dennis G. Rears" wrote in ...

I've heard that some dealers (mainly from the major coin advertisers) dip
coins. Supposely dipping is different from cleaning coins.

Dipping is a non-abrasive, chemical form of cleaning. It is doubtful that
many dealers actually engage in this practice, but often buy cleaned/dipped
coins at a dime on the dollar and then resell them for 80% of book, as they
know such coins will never get into a respected holder.

A year ago I

bought a 1934-2006 Lincoln cent set in a Dansco album labeled 1909-2007. I
was missing 70 coins from 1909-1933. I've been buying them from various
dealers but wondering what the effect of dipping is. I've read that
dipping can make an ef/AU coin look UNC+. Comments?

Dipping, if done carefully by an experienced person, can result in an
improvement in the eyes of some, but not all. Even the top-tier slabbers
will holder a dipped coin if they don't perceive any damage. Repeated
dipping, though, eventually causes the coin to cross the line to being
non-slabbable. And only coins with a fairly high silver content will dip
out properly. Dipped nickel coins, and especially dipped bronze/coppers
almost always turn ugly colors after a short time, if not immediately.

James

I know 2 sorts of dips. One is simply to use a mild detergent
(Kodak's Photoflo solution comes to mind, but there are others). That
has some prospect for removing grease and dirt if used with hot water
and no rubbing, it need not affect a coin that is primarily a noble
metal.

Not all coins are primarily noble metals. The base metals are
reactive and reactions are expedited by water as it hold soluble ions
close to the metal. Many nominally silver or gold coins contain
appreciable amounts (even a majority in some cases) of base metal.

One should not be too worried about a circulated silver coin as some
corrosion reactions will proceed with time in any case (sometimes
affectionately referred to by coin enthusiasts as "toning").

With silver coins there are other sorts of dips. Typically these are
designed to dissolve silver oxides (photographic hypo is a type of
this). The more relevant oxide of silver is the sulphide (sulpher
chemistry resembles oxygen chemistry in some superficial ways).
Sulphides are less easily removed than the clorides and bromides used
in photo emulsions and the agents used are a bit more aggressive.

To remove the suphides, means dissolving entire silver sulphide
molecules. If they are sparse on a surface, you might think that even
a microscope will not see that, although there are 2 problems with
this conjecture. The first is that if they were sparse you would not
really notice the tone. The other is the agents which dissolve the
sulphides also dissolve some silver. How long they spend in the dip
and how well they are subsequently washed are also factors.

So, if you have a coin that is seriously dark, and you dip it, you
remove all of the sulphides and the silver they bond with. You will
likely remove some additional silver. The sulphide and what else is
removed happen more or less at random, so the net effect is to roughen
the surface slightly. If you started with a proof coin, well it
really isn't one any more. Such a dip cannot improve a coin. If it
is a well-worn coin it may look a little more pleasing, but in the end
there will be less silver in the coin.

What the dips will do to any base metal really can only be settled by
experiment. The base metal would likely react even more than with
silver and the washing (necessary to remove the stuff and stop and
reaction).

On worn silver coins, its hard to fault using a little detergent if
applied with care. In any other situation it seems like dipping can
only hurt. Even so, there are other solvents that I haven't tried or
mentioned; it may be that there is a better way.