As most of you know I do a lot of electrolysis. I've not responded here because of being very busy and also wanting to see what others said. There were many good points raised here and I don't have much to add but will add a couple thoughts I do have.
A) It must be remembered that iron is a very porous material. Not as porous as Swiss cheese or a sponge but still it has the ability soak up fluids. This is how it absorbs the salts that will wreak havoc on the coastal recovered shells while metals like copper, brass, etc. aren't much harmed by it. This is important relating to a couple things mentioned by others:
1) Polyurethane will keep out the moisture but will keep it in as well. Many times we dry the outside well but forget about moisture in the cavity that will take a long time to get out especially if the only exit is a small disarming hole and the pores of the iron. Dry to the touch and dry are two different things.
2) Polyurethane put on by spray leaves a nice thin finish that looks good to many. But a spray is a bunch of droplets that don't actually coat completely without multiple coats and thus leave pores open for water penetration from humidity or sweating.
3) I have seen waxed shells rust as well for the same reasons as mentioned in #2 above. If applied by submersing in hot wax I doubt this will be an issue but if applied with a rag on a hot shell I can certainly see where there will be incomplete coverage.
B) For most of us we operate on limited budget, floor space and time so we have to choose a preservation method that we can handle which will yield acceptable results. This is why most people can clean a shell found on the side of Rocky Face but not many can take on something from the Charleston marshes.
C) As I've told a few people over the years cleaning and conserving are not the same thing. A poor man's definition (I'm sure Jim J. can give a better technical explanation) is that cleaning removes what is exterior to the artifact while conservation preserves the artifact itself. Some artifacts need little conserving and some need huge efforts (see Hunley for a good example of huge on many scales). I consider myself a good cleaner (there are better) but would not say that about my conservation skills. I'm very much a newbie there and when I get more time I intend to get more practice.
Just some rambling thoughts. I've not posted in a while and wanted to respond. Thanks for the great information from some people with a ton of experience.
