How to clean shells ?

Original Forum Question : How do you clean regular sea-shells without bleach? (I like the colors!) DO you just rinse them in water or is there something special you should do?

Bleach is the best all around cleaning solution for shells. It doesn't harm the colors of the shells. It does remove periostracum, but on a shell with periostracum you can't see the colors anyway. Still, some serious collectors do like to have some specimenas with periostracum, and such specimens have to be cleaned without bleach. Bleach also removes many kinds of encrusting organisms as well as algae, ordinary mud and dirt, and most importantly, it removes any remaining soft parts of the animal from within the shell, thereby avoiding unpleasant odors. You don't have to use the bleach full strength. 1 part bleach to 10 parts water is sufficiently strong for most cleaning jobs. But stronger solutions can be used without harm to the shells. There are some exceptions. I don't use bleach on very thin, translucent shells, or on shells with a nacreous interior like pearl oysters and abalone. If you are nervous about using bleach, try it on a few less desirable specimens until you gain some confidence in the technique. After bleaching, just flush with water inside and out, and dry.
If the whole animal is in the shell, it has to be removed before using bleach. The usual ways of accomplishing this are: cooking – start with room temperature water, put the shells in, bring to near boiling, then cool gradually. Avoid sudden temperature changes, or the shells may crack. Don't drop them into near boiling water, and don't remove them from very hot water and immediately rinse them with cold water. After cooking and cooling, the animal can usually be shaken or flushed or picked out of the shell with a narrow sharp instrument.

freeze/thaw – overnight in the freezer, then thaw at room temperature, after which the animal can be shaken/flushed/picked out of the shell.

microwave – some collectors like this method. I have tried it a few times. It's fast, and it seems ok for reasonably solid shells. But more fragile shells are likely to crack/break/explode, in my experience. put the shells inside a plastic container to prevent snail parts spattering all over the inside of your microwave.

You may find some more tips in the shell cleaning section of this website (beginners'topic).
(Answer by M. Paul Monfils via the Forum)

Original Forum Question : I recently found some shells on my honeymoon in the Carribean and need some advice on cleaning. The first is a cowrie that I found while snorkling. It is dead and has no meat inside of it, but it is encrusted with hard coral. I have always read that you need to be careful when cleaning cowries, but I have never found any advice on how to clean them. The second is a sea biscuit that was found freshly dead (I had to scrape some of the spines off it). I imagine that it could be put into a bleach solution, but I do not want to bleach it white and lose it's dark color. Any advice on cleaning/preserving would be greatly appreciated. Thanks in advance!!!

Yes that cowrie is certainly in need of some cleaning! The problem in removing this kind of calcareous encrustation is that it is composed of the same material as the shell – calcium salts – and therefore any chemical that will dissolve the encrustations will also dissolve the shell. So chemical cleaning methods are out. Only physical methods can be used on something like this. That having been said, it is possible, depending on the type of encrustation, that a pretreatment with bleach will loosen or soften the encrustations somewhat, making subsequent physical methods a bit easier. This is because such encrustations often have a small proteinaceous component, and the bleach will dissolve out the proteins though it won't dissolve the actual calcium salts. With or without pre-bleaching, physical methods must follow. If you have access to one, I would first try an ultrasonic cleaner, to see how much of the encrustation will be removed by that means. If any of it comes off, continue to use the USC for a longer period of time. After that, if some of the white stuff still remains, patient picking with a sharp tool or scraping with a small sharp blade is about the only way of getting the stuff off, bit by bit. Most likely the gloss of this shell is already damaged, and no matter how carefully you clean it, it won't look like a live-taken cowrie.
Now, the sea biscuit – The test (shell) of this animal is actually white. The dark color is due to a layer of microscopic brown spines attached to the test, and associated muscle fibers and other soft tissue. Using bleach removes all the spines and tissues, and leaves just the white test. However, if you want to keep the specimen "natural", it isn't difficult to do. I usually soak such specimens in formalin for a few days, then alcohol for a few days. But I realize not all people have access to formalin, and also it is smelly and irritating and somewhat toxic. If you do have formalin and know how to use it, I believe that gives the best preservation. However, good results can also be obtained using alcohol alone. In that case, soak the specimen in alcohol for about a week, changing the alcohol at least once, after the first couple of days. Ethyl alcohol is best but isopropyl alcohol is adequate. Avoid methyl alcohol, which is sold as shellac thinner. The alcohol concentration should be at least 70%. "Rubbing alcohol" from the pharmacy works satisfactorily. Once the specimen is preserved in the alcohol, it can be removed, drained, and then dried thoroughly in a warm, dry area. Outdoors is good, weather permitting, but it can be dried indoors too. However, in specimens prepared in this way the spines are not too securely attached to the test, and tend to gradually fall off, especially if the specimen is handled much. So I use an additional procedure to prevent that. I remove the specimen from the alcohol, soak it in water overnight to remove the alcohol, then soak it in 10% Elmer's Glue-all (10% glue, 90% water) for a couple of hours, then drain and dry. The glue dries invisible, but strenghtens the spine-to-test attachment. Other brands of white glue, like Sobo Glue, are equally good. (Chemically this is polyvinyl acetate). If you use glue, dry the specimen on a non-stick surface like wax paper, so you don't end up with the specimen glued to whatever surface it is lying on.
(Answer by M. Paul Monfils via the Forum)