A futon mattress is a Japanese-style mattress that is designed to be foldable so that one can put it out of the way during the day. Generally they're flat. They are usually only about 2 inches thick. They have an exterior of fabric, and they are stuffed with some kind of filling such as cotton or husks like buckwheat chaff or beans or even plastic beads.
The Western futon, however, is a little bit different. Generally they are thicker, filled with a little bit more sturdy material, and are designed to be placed on structures that fold into a couch, and then flatten into a bed. The material that covers the outside of a futon mattress is designed to be flexible so that it can be used as both a sitting surface, and to be converted into a bed that night. Western futons are much thicker than many traditional Japanese futons.
A cheap futon mattress can be a great investment because of how little it costs to get the functionality of both a couch and bed. However, certain care should be taken to lengthen the use of a futon mattress. For example, the mattress should be rotated in order to change where the crease false. Failing to rotate can result in an uncomfortable crease in the mattress.
Futon mattresses can be cleaned, by any means you choose to clean them, as long as you don't get the inside of the mattress wet. It is better to use a damp cloth and wipe the surface, and to use too much liquid. If the interior of the mattress gets wet, you will have a risk of developing mold or mildew inside the mattress, which can cause health concerns.
One consideration when buying a futon mattress is to get a no slip pad. This prevents the mattress from sliding around when using it as both a bed, and has a sofa. Some people do have problems with the futon mattresses slipping off of the frame when positioned upright like a couch. That is what the no slip covers protect against.
Generally speaking most of the manufacturers of cheap futon mattresses have the same degree of quality and comfort. There is minimal difference between makes and models. More important is to find one that feels comfortable to you, and it has the external features you need, such as the right exterior shell material, and the correct exterior color to match your décor.
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