Polystyrene, also know as styrofoam, is a thermoplastic material that is solid at room temperature, turns to liquid when heated, and becomes glass-like and subject to fracture when frozen. Polystyrene is used in a wide array of products from smoke detectors, plastic cutlery, and take-out containers to CD jewel cases. Polystyrene beads can expand into foam for use in such items as stuffed animals and packing peanuts. Beanbag chairs (once made with real beans) now rely on polystyrene beads for their filling, which gives beanbags their shifty, squishy resilience while making them so comfortable to sit in.
Decide on the type of polystyrene bead you will use. Virgin polystyrene beads are perfectly round, smooth pellets about 3 mm in size that shift more easily around each other. They also keep their shape better and longer, preventing your beanbag chair from flattening prematurely. Virgin polystyrene beads are a higher quality and will last longer, costing £8.10 to £9 per cubic foot.
Reground polystyrene beads are not pre-used but come from large blocks of polystyrene (styrofoam) that are broken down to beads typically 3--4 mm in size. This method causes pellets to stick together, which prevents the beads from shifting as easily around each other. Reground polystyrene beads are cheaper (11.70 to £8.70 per cubic foot), but have a shorter shelf life.
Measure your beanbag chair. Sit on the chair and then stand up. Measure the middle (width) of the largest portion.
Determine how much refill polystyrene you will need. Refer to the table shown here.
Purchase your polystyrene. Purchasing online can prove to be more convenient, and even cheaper, than buying at local craft stores. Online retailers such as Bean Bags Only, Roseann's Dolls and Bears, and Serenity Health offer virgin polystyrene beads at roughly the same price per cubic foot. Remember that online purchases usually bring the extra cost of shipping to the price tag. However, local retailers may not offer the same options as their online counterparts: virgin polystyrene beads, varying quantities, and discounted prices.
The polystyrene beads in a beanbag chair flatten and begin to break down as they are crushed and air is squeezed from them. They will eventually need replacing, approximately every two years.
Polystyrene beads can become a choking hazard for children under the age of three. Make sure the polystyrene beads you buy comply with United States Flammability standards and CPSC Guidelines for zipper closures (see resources). Polystyrene beads are not biodegradable and are not recyclable.