The best materials for storing and repairing shells are those that do not harm the shell, even after many years have passed. Whatever you do should also be reversible. Rubber bands deteriorate badly within a few years, eventually turning into strips of brittle material that are stuck to the shell. The transformation can be delayed by placing the specimen in darkness, but eventually this will happen. Glues work because they react with the surface of the shell, so it's a good idea not to use them for keeping valves together. (Even the "temporary" glue on yellow sticky-tab paper will glue permanently onto your book pages within about 5 years, as I have discovered by experience.) Wax is a special case. It is not very reactive, but it is also very difficult to remove from surfaces later on, so anything you do with wax (or silicone, for that matter) must be considered as irreversible. I have seen string used to hold unionids together, with no harm to the shell after about 70 years. This string has a peculiar golden color, and I do not know its composition or brand name. In many collections, gravity is used to keep valves together, with one valve resting on the other, both with the interior of the shell oriented downward. I don't recommend this in earthquake country, or in collections where people handle the shells often. But if you write the specimen number on both valves, they can always be reunited. The collector can simply store each pair of valves in its own box, bag, tray, or compartment. Ideally, paper containers should be of archival quality (not acidic); we have discussed suppliers of chipboard trays and rag paper in previous threads. Wood is not recommended in the very long term, especially acidic wood like oak. Metal works well, at least as a cabinet material. Plastics are of diverse compositions, and some of them deteriorate rapidly, which is not good when you are using bags to keep the shells separate. Other plastics are of archival quality. I have had some plastic bags split in the dark in only ten years. As to cotton, the Conch-L archives have a thread on that too, with mixed reports. Some cotton seems to be low enough in acid to work well for a hundred years, but some people have had bad experiences with the stuff. Catalogs of archival-quality materials are distributed to librarians and museum curators. I haven't checked, but they are probably accessible through the Web now. I was amused to hear about the recycling of fast-food containers for use in the shell collection. This is a great way for a beginner or someone with limited resources to get started in shell collecting. As a poor grad student, I used to save plastic vegetable trays from the grocery store, and would cut the bottoms off waxed-paper milk and juice containers for use as small square trays. After thorough washing, they worked very well for a few years, until I replaced them with chipboard trays. Anyone who collects fossils knows that some rocks are acidic. Fresh sandstone and shale commonly contains pyrite, which oxidizes in the atmosphere to iron oxide (rust) and sulfuric acid. After a few years, opening a drawer full of such specimens yields a sour odor, and your fresh, bluish-gray rocks have turned yellowish-brown! Where the shells have been replaced by iron sulfide (pyrite or marcasite), the fossils themselves are the problem. When freshly collected, these fossils are colored a beautiful brass-yellow. After a few decades, they convert to a pile of greenish-gray dust in a badly discolored paper tray, with a more or less shell-shaped hole eaten through the underlying paper label. The inevitable can be staved off by various chemical means, but generally not forever. On the whole, it is best to store such specimens separate from any specimen that might be damaged by acid vapors. But most fossils in limestone can be stored along with modern shells without fear of harming them, so far as I know. This has been an interesting thread. I'd like to hear from museum curators, shell dealers, and others who deal with decades-old collections about their preferences for very long-term storage of paired valves. For instance: Does string work for several decades for specimens that do not have a protective periostracum? Andrew K. Rindsberg Geological Survey of Alabama Tuscaloosa, Alabama, USA