Dear Christopher, Byne's "disease" is an efflorescent breakdown of calcium
carbonate structures, most often noticed in malacology collections such as
the archaeological clamshells you mentioned. The classic conditions for
this are storage of shells with some salt exposure (either from a marine
environment or from soils with a lot of evaporite deposits) in an acidic
environment (such as an oak cabinet). There is the most unbelievable body
of misinformation on the subject (starting with L. St. George Byne
himself), so much so that I published a paper in _Festivus_ solely on the
bad science surrounding the problem.

Punching holes in a bag won't do a thing to help the problem and may
hasten it along if the specimen is in a wooden cabinet. (One of the
things I teach in the anoxic storage course is the whole principle of
creating microenvironments to protect specimens when the macroenvironment
is poor. Putting shells in bags to protect them from the internal case
environment is a good way to deal economically with an inferior case.
Punching holes in those bags just undid everything you did right.)

Byne's is not a disease, not bacterial, does not spread from specimen to
specimen, and is not best addressed by caustic treatments or surface
coatings. It is a complex process in which calcium carbonate reacts with
acidic vapors to form salts such as calcium acetate and calcium formate,
which disruptively crystallize, destroying part of the surface of the
specimen. The exact mechanism for this is being worked on; I believe that
Dave Von Endt at CAL is one of the movers on this. Tennent and Baird
published an excellent article on this, but I think that Dave's work will
show that the process is even more complex.

In the meantime, keep your shells in as inert an environment as you can
manage, and keep the relative humidity under 45%, especially if the shells
are already reactive (RH does seem to drive the rate of the reaction). You
can brush off the reaction product (don't rinse or wash the shells),
accepting that the damage is irreversible. We're working now on
determining whether anoxia affects the rate of reaction in affected
shells.

I can send you copies of both the Festivus paper and the Tennent and
Baird paper if you're interested; let me know off-line to spare everyone
else.

Don't punch holes in your bags. Sally Baulch is correct in pointing out
that some highly reactive and interactive things do not do well in
microenvironments, in which case they shouldn't be in bags in the first
place. For mollusk shells, inert bags should be fine.

Cheers,
Sally Shelton
Director, Collections Care and Conservation
President-Elect, Society for the Preservation of Natural HIstory Collections





-------------------------------------------------------------------------
|                                                                       |
|                 San Diego Natural History Museum                      |
|                          P. O. Box 1390                               |
|                San Diego, California   92112  USA                     |
|             phone (619) 232-3821; FAX (619) 232-0248                  |
|                     email [log in to unmask]                          |
|                                                                       |
-------------------------------------------------------------------------