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If you've got more books than you know what to do with, the best place to store them is in opaque plastic tubs that you can seal and store in a cool location. Plastic tubs help to protect books from sunlight, rodents, and other conditions, and are easy to stack in out-of-the-way locations. If you don't need to access your books regularly, plastic tubs are a good choice.  Most retailers sell a variety of storage bins, in various sizes. Try to get relatively small boxes, no bigger than 12 x 12 in., or the bins will become quite heavy. It's fine to store these books anywhere the temperature will be consistent and cool. Attics and garages will be fine in certain climates. Polyurethane plastic tubs should protect books adequately from insects and rodents who might chew up books. Got more books than you've got shelves? Finding a spot for all those old paperbacks can be tough. But with the right storage techniques, you can find places for them.  Store book bins underneath the bed, at the backs of closets, or in the basement. Try to store books indoors, if you can. Exposed attic spaces, sheds, and garages can have drastic temperature swings, which can be rough on the binding and paper. Consider renting a storage space in your town for storing books. If you have a lot of books, an indoor storage facility might be temperature-controlled and appropriate for some old boxes of books, while outdoor garages might be fine for your old paperbacks. In very hot climates, books can start to warp. Ideally, you should keep the relative humidity around 35%. Humidity causes binding to warp, paper to curl, pages to mould and books to suffer. Ideally, you want to keep your books stored long-term in a climate-controlled room, kept around 35% humidity. Good dry air circulation is good for books. Anything lower than 50-60% should be okay for most books, but rare or valuable books should always be stored around 35%, indoors. If you're really particular about keeping your books safe, though, Try to keep it even lower if possible. Books stored close to heat ducts, hot appliances, and other sources of direct heat can become warped. To protect the binding of your books, keep them stored in relatively cool temperatures. In most climates, a room temperature of 60-75 degrees is perfectly fine. If you are concerned about the distribution of heat in a particular room and the safety of your books, rotate them regularly to make sure a handful of books aren't getting more exposed than others. Soft room lighting won't affect the quality of books much. But hard, direct sunlight will always serve to bleach out and damage the binding and the page-quality of books. Rooms in which books are kept should be shady, with drapes over the windows to protect the books. The best way to store books? Flat on their back, or standing up on their "tail", the bottom edge of the book. This means the books is stored standing upright, so you can read the spine correctly. Books are designed to be stored in this way, and can be supported by other books, helping to keep them stable and safe. Never store books with the binding or spine pointing up. This will always crack the hinge, which will affect the life of the book. Certain types of book binding glue and paper are often an attractive snack for cockroaches, silverfish, various beetles and other insects. In most conditions, you won't have to worry much about protecting your books from infestation, but it's still a good idea to keep food and crumbs out of the book room to keep insects from coming in. Very rare books, or books that you're concerned about keeping safe from infestation should be stored in plastic sleeves. Custom enclosures are also available at most rare book stores, made to fit the specific volumes you've got. If you find that some of your books have been infested with insects, the best way to clean them out is to place them in plastic bags and put them in the freezer for several hours to kill the bugs, then clean them thoroughly. Read the next section for more information about cleaning books properly. If you have some first editions or especially rare books that you're concerned bout taking care of yourself, consider enlisting a professional to care for your books for you. Museums, libraries, and private rare book collectors may be a better place for those items than the garage. The American Institute for Conservation (AIC) collects rare artistic and historical works, and offers a variety of conservators you can enlist to guide you through the process of caring for them.

Summary:
Store books long-term in plastic bins. Find an appropriate space for storing your bins of books. Keep books in rooms with relatively low humidity. Keep books away from direct heat. Reduce exposure to direct light. Store books upright or flat. Protect books from bookworms. Store rare books in custom sleeves. Consider finding a conservator for very rare items.