11. Water and air beds provide infinite contouring on their own.
True. But deep contouring can also create some problems for them. Both air and water operate within enclosed reservoirs. The volume of fluid that is displaced by a hip or a shoulder moves to another unpressured part of the bed, usually the corners, and can distort the shape of the sleep surface.
It generally produces a 'hammock' or sag effect, exactly what you don't want for natural spine alignment. At the same time, this action can also tighten the surface causing a tough membrane that can actually work against comfort. However, a number of engineering refinements, including isolated and separate chamber reservoirs, and foam toppers, have greatly reduced both the distortion and the membrane feeling in these flotation systems.
In foam flotation, the volume of air displaced by the same hip or shoulder moves easily through the open cell structure of the foam and is vented to the atmosphere without distorting the shape of the sleep surface or support system.
12. What has foam meant to the bedding industry?
13. Some other considerations were mentioned as possible support criteria.
Yes. Support should be independent. Unequal weight, or toss and turn activity should be restricted to the individual, and not influence the other sleeping partner. Only foam, without a rigid connected structure, and with its ability to react only to the immediate area of applied pressure, or weight, makes these attributes a practical reality.
14. Comfort, support, unequal weight partners, isolated activity. What other sleep attributes should be considered?
Those are definitely the majors. But I would also include a couple of others. Noise is something every bed should be without. Another is moving response. When you move in bed, the surface literally follows you around. Its reaction to your moves can range from 'bouncy' to 'tranquil'. Foam is quiet, and with its lack of moving parts and accompanying inertia it reacts very gently to body movement.
In summary, those are the sleep benefits that quality sleep products should offer. They may, or may not line up with the attributes as seen by the merchandiser, or the consumer. The uncomfortable, overly firm bed is still very much in vogue.