A mattress is a mat or pad, usually placed atop a bed, upon which to sleep or lie.

The word mattress is derived from Arabic words meaning "to throw" and "place where something is thrown" or "mat, cushion." During the Crusades, Europeans adopted the Arabic method of sleeping on cushions thrown on the floor, and the word materas eventually descended into Middle English through the Romance languages.

Though a mattress may be placed directly on the floor, it is usually placed atop a platform (such as a bed or a metal spring foundation) to be further from the ground. Historically, mattresses have been filled with a variety of natural materials, including straw and feathers. Modern mattresses usually contain either an innerspring core or materials such as latex, viscoelastic, or other polyurethane-type foams. Mattresses may also be filled with air or water.

Components of an innerspring mattress

common innerspring mattress consists of three components: the spring core, the foundation, and the upholstery layers.

Spring mattress core

The core of the mattress supports the sleeper’s body. Modern spring mattress cores, often called "innersprings," are made up of steel coil springs, or "coils."

The quotation below, borrowed from The Mattress & Sleep Company - Myths & Concerns talks about how coil count maybe isn't as important as most people are led to believe.

Although coil count is a consideration one might have when choosing a new mattress, it certainly should not be the deciding factor. Keep in mind that there are a number of different factors that contribute to the comfort, durability and support offered by a particular innerspring.

Innerspring (coil) design, gauge (thickness) of wire, number of turns, metal composition, tempering, and so on, all contribute to the potential of a particular innerspring.

Also keep in mind that as the coil count increases, the diameter of each individual coil will decrease. You still have to fit all of those springs in the same amount of space!

An interesting fact: Vera Wang by Serta, a highly regarded brand, feature queen size beds with “only” 532 coils. Stearns & Foster, another highly regarded brand, feature queen size beds with “only” 504 coils.

The gauge of the coils is another factor which determines firmness and support. Coils are measured in quarter increments. The lower the number, the thicker the spring. In general, higher-quality mattress coils have a 14-gauge (1.63 mm) diameter. Coils of 14 to 15.5-gauge (1.63 to 1.37 mm) give more easily under pressure, while a 12.5-gauge (1.94 mm) coil, the thickest typically available, feels quite firm.

Connections between the coils help the mattress retain its shape. Most coils are connected by interconnecting wires; pocketed coils are not connected, but the pockets preserve the mattress shape.

Types of coils

There are four different types of mattress coils:

　　· Bonnell coils are the oldest and most common. First adapted from buggy seat springs of the 19th century, they are still prevalent in less expensive mattresses. Bonnell coils are hourglass-shaped, and the ends of the wire are knotted or wrapped around the top and bottom circular portion of the coil and self-tied.

　　· Marshall coils, also called "pocketed coils," are each wrapped in a fabric encasement and usually are tempered, or in the case of the Simmons Beautyrest carbon magnesium is added. Some manufacturers pre-compress these coils, which makes the mattress firmer and allows for motion separation between the sides of the bed.

　　· Offset coils are designed to hinge, thus conforming to body shape. They are very sturdy, stable innersprings that provide great support.

　　· Continuous coils Or Mira-coils, Work by a hinging effect, similar to that of offset coils. In a basic sense a continuous coil is simply that, one continuous coil in and up and down fashion forming one row (usually from head to toe) of what appear to be invidiual coils. The advantages of how firm a support the continuous coil provides it is somewhat tempered with the 'noise' associated from a typical mira coil unit.

Air mattresses

Air mattresses use an air chamber instead of springs to provide support. Quality and price can range from very cheap ones that are used for camping and temporary places to sleep all the way up to high-end luxury beds. The price is generally comparable to that of inner-spring mattresses.

Recent innovations to air beds include the ability to adjust the firmness of the mattress, and the ability to maintain different settings for each side of a larger mattress. One such company is Select Comfort. They were established in 1987 and sell a patented adjustable, air-chamber designed sleep system.

Foam mattresses

Foam mattresses use latex foam or viscoelastic memory foam instead of springs to provide support. Since foam varies in quality, prices can vary widely. Most mattress manufacturers offer a line of memory foam mattresses.

Foundation

There are three main types of foundations.

　　· Box-springs consist of a rigid frame which contains extra-heavy-duty springs. This type of foundation contributes to softer support and a bouncier mattress. Because box-springs can cause mattresses to sag, many manufacturers add high-density block foam underneath the coils or provide a rigid foundation instead.

　　· Traditional wood foundations are usually made of soft woods, such as pine, or hard woods, such as poplar. They usually consist of seven or eight support slats covered with cardboard or beaverboard. This type of foundation, called a zero deflection unit or an "Ortho Box" in the bed industry, increases the feeling of firmness and stability.

　　· Grid foundations are a combination of steel and wood.

Upholstery layers

Upholstery layers cover the mattress and provide cushioning and comfort. Some manufacturers call the mattress core the "support layer" and the upholstery layer the "comfort layer." The upholstery layer consists of three parts: the insulator, the middle upholstery, and the quilt.

The insulator separates the mattress core from the middle upholstery. It is usually made of fiber or mesh and is intended to keep the middle upholstery in place.

The middle upholstery comprises all the material between the insulator and the quilt. It is usually made from materials which are intended to provide comfort to the sleeper, including regular foam, viscoelastic foam, felt, polyester fibers, cotton fibers, convoluted (“egg-crate”) foam, and non-woven fiber pads.

The quilt is the top layer of the mattress. Made of light foam or fibers stitched to the underside of the ticking, it provides a soft surface texture to the mattress and can be found in varying degrees of firmness. The protective fabric cover which encases the mattress is called ticking. It is usually made to match the foundation and comes in a wide variety of colors and styles. Most ticking is made of synthetic fibers like polyester, or acrylic; or of natural materials such as latex, cotton, silk, and wool.

Mattress quality

Many parameters determine mattress quality. Laboratory test methods have been established for some of these parameters, such as pressure distribution, skin microclimate, hygiene, edge support, and long-term stability. Many of these have been developed by Dr. Duncan Bain, working on behalf of the UK's Medicines and Healthcare products Regulatory Agency.

Other parameters, such as firmness, are more specific to the sleeper. In general, firm mattresses are recommended for stomach and some back sleepers, soft mattresses are recommended for side sleepers, and medium mattresses are recommended for the majority of back sleepers. Some brands offer mattresses with one softer side and one firmer side, or with adjustable firmness levels, to accommodate sleepers who share a bed.

Special mattresses used in hospitals

"Not all the anti-decubitus mattresses really succeed in reducing the interface pressure. The foam and gel mattresses have no or limited pressure reducing qualities. The polyether mattress and especially the polyurethane slow foam mattress reduce pressure best and are preferable in the prevention of pressure ulcers on an operating table. None of the mattresses tested reduced the pressure sufficiently in lateral position."

Maintenance and care

The Better Sleep Council suggests that a quality mattress should provide 8 to 10 years of good support and comfort. This is an approximation, as many different things may factor into the lifespan one may expect to receive from their mattress.

Mattresses should be placed atop a firm base to prevent sagging. Mattresses should be rotated approximately once every three months to ensure even wear; in addition, two sided mattresses should be turned over (flipped) twice per year. Folding and bending of the mattress should be avoided if possible, as should heavy wear in one spot and excessive weight on the handles. Mattresses should not be soaked, lest mildew develop inside the upholstery; instead, they can be cleaned with a vacuum or with mild surface cleanser and a slightly damp cloth. Mattress Protectors help prevent stains and soiling of the ticking.

Once a mattress no longer feels supportive and instead seems to contribute to body pain or stiffness, it should be replaced. Some symptoms of a broken or worn out mattress include springs which can be felt poking through the upholstery layer, visible permanent sagging or deformity, lumpiness, and excessive squeaking.