How to protect a coin with a patina as brittle as THIS??

[Rupert]

Here's a coin that I received today, which gives me joy and pain alike.

It's a Commodus sestertius, a big coin with an especially beautiful portrait of the young co-emperor from 177AD (and a less well preserved rare Iuno Sispita reverse, RIC MA 1583). It has a black patina with some damages to the edge, as is rather common with brass coins. But the one feature I've never seen before is the obverse, especially the field in front of the head, that has a structure like a dried-out mud pool with many small cracks. It's very clear that the information is ONLY in the patina and that removing the patina would leave a crater landscape. So the first thing to do is not drop the coin, all right. Is there anything else I can do to keep the remaining patina from breaking loose? Waxes, resins, anything?

Thanks in advance,

Rupert

[mwilson603]

Rupert,
I am not going to pretend to be an expert conserver, however I have had coins I have cleaned with very brittle surfaces and I found that a sligtly warmed bit of Renwax, allowed to almost melt onto the coin, seemed to help bond the coins surface to the coin.
If done carefully, i.e. just enough wax allowed to melt slowly onto and into the coin, you may also not need to buff the coin so you could avoid that very shiny surface you sometimes see with waxed coins.  I used to put my coins on top of a glass lampshade to allow the coin to slowly warm up, and then carefully place small dabs of wax onto the coin surface, rubbing in gently with small circular motions of a fingertip.
I also remember someone saying that they were going to try preserving a brittle surfaced coin with wood preserver.  I am not sure of anyone actually trying this but in theory I could see how this could work.
regards
Mark

[renegade3220]

I think that good advice has already been given.  No expert conservator here either, but the only safe way to "seal" a coin per say that I know of is to wax it.

Now, as far as using Ren Wax, I would personally recommed Conservator's Wax in this instance.  It is the same stuff, but I use it instead.  From my understanding it is a little more jelly like to begin with so may be easier to apply in this case.  You could always warm the wax slightly as well to soften it up to apply it easy.  It will turn almost mayonase like.

Also, if you are aftraid to heat this coin up due to small thermal expansion that may occur and possilbly crack or pop pieces off of the coin, then put a very thin layer of wax on it and then melt the wax onto the coin with a blow dryer.  This, IMO, will keep the coin cooler, but melt the wax to the same effect.

I have only done a few coins with Con Wax, but I never really found buffing necessary.  I think they look good without the buff.  Just my opinion.