Oops! I didn't know I had sent this, but since I did, I guess I better
finish it . . .

You have probably noticed that many shells look more colorful when wet than
they do after drying out.  Oiling a shell maintains that "saturated"
appearance ("wetting" the shell with something that will not evaporate), and
thereby keeps the colors looking bright. Oiling has little if any effect on
shells which are naturally glossy, like cowries and olives, and are also in
good condition. It may bring out the color in a beach-worn cowrie or olive,
but it will not restore the natural gloss. It also has little visible effect
on shells which have little natural pigmentation. But on shells which are
colorful and porous, like pectens, many volutes, etc, the oil can often make
a major difference in the appearance of the shell. Oiling will also mask
scratches and dull spots on glossy shells (buyer beware), or glossy
apertures, just as furniture polish does. In fact, there is a furniture
polish that some collectors like to use for oiling shells. I don't remember
the exact name, but I believe it contains the word "gold". Baby oil works
fine, if you want your collection to smell like a nursery. But paraffin oil
and mineral oil are odorless and work equally well. Don't use plant oils
like vegetable oil or olive oil. They may make the shell look good
initially, but later they may become rancid, and develop a dark color, and
possibly an odor. Many people like to dilute the oil with a solvent, to make
it less viscous and help it penetrate better. Lighter fluid is often used,
since it is readily available. Paint thinner or kerosene will also work. I
use xylene, since I have it in quantity at work. Alcohol won't work because
it won't mix with oil. After application, the solvent evaporates away fairly
quickly, leaving the oil behind. Penetration is the key. You want the oil IN
the shell, not ON the shell, that is to say, you want it to penetrate into
the actual matrix of the shell - but not to remain on the outer surface,
where it will attract dust and leave oil spots in your fingers and cabinet.
Apply the oil liberally, rub it into the shell, then wipe off ALL the oil
you can, with a soft absorbent cloth. For shells that are frilly or spiny,
where it is difficult to wipe off the oil, apply the oil with a brush, give
it a little time to penetrate, then rinse the shell thoroughly under a
powerful water spray. Oil and water don't mix of course, but the force of a
powerful spray can nevertheless dislodge most of the excess oil on the outer
surface of a shell, without removing the oil that has penetrated into the
pores of the shell. If you put oil on a highly porous shell (one that
normally appears rather "chalky", like Buccinum undatum or Tagelus plebeius
- or long-dead beach-collected shells), the shell will absorb lots of oil,
and just look "oily", not natural. Fortunately, oiling can easily be undone
by washing in warm water and dish detergent.

Paul M.