Traditional, all-cotton Japanese futons tend to be very firm. They are one of the heaviest types of futons. A twin size can weigh between 38 to 45 pounds and a queen-size futon can tip the scales at 75 pounds. Once futons started to catch on in America, manufacturers started to combine foam with the cotton.
This cotton and foam combination tends to be the most popular type of futon on the market. Cotton does tend to clump, so these futons need to be rotated at least once a month. Setting the mattress in the sun at least once a year also helps the cotton fibers "plump up."
Futons that have an innerspring center feel more like a traditional mattress. They tend to be more expensive than the cotton and foam variety but are easier and more comfortable to sleep on for those used to sleeping on a traditional bed.
A well-made innerspring futon mattress has polyester batting for the outer layers, thick foam barriers for comfort and springs that are individually wrapped, or pocketed, usually in cotton fabric.
Futons are now being made with viscoelastic or memory foam. This material conforms to individual body shapes and even gets softer with the heat of your body. Originally designed to cushion astronauts from the g-forces experienced in spaceflight, viscoelastic foam eventually found its way into the consumer market in the form of mattress covers, pillows and even ear plugs.
Viscoelastic foam, when used as the outer layers on stacks of conventional foam, creates a comfortable sleeping area that also regains its original shape after the sleeper gets up. These futon mattresses are more expensive but require less care than the traditional models.