A mattress is a large, rectangular pad for supporting the reclining body, designed to be used as a bed or on a bed frame, as part of a bed. Mattresses may consist of a quilted or similarly fastened case, usually of heavy cloth, that contains materials such as hair, straw, cotton, foam rubber, or a framework of metal springs. Mattresses may also be filled with air or water.
Mattresses are usually placed on top of a bed base which may be solid, as in the case of a platform bed, or elastic, such as an upholstered wood and wire box spring or a slatted foundation. Popular in Europe, a divan incorporates both mattress and foundation in a single upholstered, footed unit. Divans have at least one innerspring layer as well as cushioning materials. They may be supplied with a secondary mattress and/or a removable “topper.” Mattresses may also be filled with air or water, or a variety of natural fibers, such as in futons. Kapok is a common mattress material in Southeast Asia, and coir in South Asia.
Innerspring mattresses commonly consist of just the spring core, and the top and bottom upholstery layers.
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 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; encased coils are not connected, but the fabric encasement helps preserve the mattress shape.
There are four 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 mid-priced mattresses. Bonnell springs are a knotted, round-top, hourglass-shaped steel wire coil. When laced together with cross wire helicals, these coils form the simplest innerspring unit, also referred to as a Bonnell unit.
- Offset coils are an hourglass type coil on which portions of the top and bottom convolutions have been flattened. In assembling the innerspring unit, these flat segments of wire are hinged together with helical wires. The hinging effect of the unit is designed to conform to body shape. LFK coils are an unknotted offset coil with a cylindrical or columnar shape.
- Continuous coils (the Leggett & Platt brand name is “Mira-coil”) is an innerspring configuration in which the rows of coils are formed from a single piece of wire. They work in a hinging effect similar to that of offset coils.
- Marshall coils, also known as wrapped or encased coils or pocket springs, are thin-gauge, barrel-shaped, knot-less coils individually encased in fabric pockets—normally a fabric from man-made, non-woven fiber. Some manufacturers pre-compress these coils, which makes the mattress firmer and allows for motion separation between the sides of the bed. As the springs are not wired together, they work more or less independently: the weight on one spring does not affect its neighbors. More than half the consumers who participated in a survey had chosen to buy pocket spring mattresses.
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 flexible polyurethane foam (which includes convoluted “egg-crate” foam), viscoelastic foam, latex foam, felt, polyester fiber, cotton fiber, wool fiber and non-woven fiber pads. In Europe and North America, mattress makers have begun incorporating gel-infused foams, soft-solid gels layered over foam, and poured gels in the top comfort layer of the bed.
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.
There are three main types of foundation or bed base:
- A traditional box spring consists of a rigid frame containing extra heavy duty springs. This foundation is often paired with an innerspring mattress, as it extends the life of the spring unit at the mattress’s core.
- An all-wood foundation usually has seven or eight support slats disposed below paperboard or beaverboard. This foundation, variously called a “no-flex”, “low-flex” or zero-deflection unit, as well as an “ortho box”, provides support similar to a platform foundation. All-wood foundations have become increasingly prevalent as U.S. mattress makers shifted to super-thick, one-sided mattresses.
- A grid-top foundation is a combination of steel and wood.
Typically the measurements of a foundation will be about 1-2″ shorter than the measurement of a mattress.
Ticking is the protective fabric cover used to encase mattresses and foundations. It is usually designed to coordinate with the foundation border fabric and comes in a wide variety of colors and styles. Mattress fabrics can be knits, damask or printed wovens, or inexpensive non-wovens. During the past decade, along with the rise in popularity of all-foam beds, stretchy knit ticking on the bed’s top panel has become a standard look on both innerspring and foam beds. Most ticking is made with polyester yarns. More expensive mattress fabrics may contain a combination of polyester with rayon, cotton, silk, wool or other natural yarns.
Until the early 2000s, beds were normally upholstered with a single fabric. This was usually a damask ticking or, for inexpensive bedsets, a non-woven fabric covering all surfaces of the mattress and foundation. Today’s bedsets are covered with up to six different fabrics: A better quality circular knit or woven damask on the top panel—the bed’s sleeping surface; a matching or contrasting [usually woven] fabric on the border of the mattress; a matching or contrasting [usually woven] fabric on the foundation side panels; a ‘non-skid’ woven or non-woven fabric on the surface of the foundation and reverse side of the mattress; and a non-woven dust cover on the under side of the foundation. Some North American mattress producers are beginning to use furniture upholstery fabrics on the bed’s borders giving beds a more European, home furnishings look.
All-foam mattresses use different weights and densities of petrochemical-based flexible polyurethane foams and viscoelastic foams or memory foam, and latex rubber foams. A number of mattress manufacturers have incorporated polyurethane and visco-elastic foams with a portion of plant-based content. All-foam mattresses are often paired with platform bases.
- Latex foam: Latex foam in mattresses is generally a blend of the latex of the Hevea brasiliensis tree and synthetic latex, which is derived from petrochemicals and other substances and fillers. There are, however, natural latex mattresses that leave out polyurethane-based chemicals. Latex foam is produced using either the Talalay or the Dunlop process.
- Memory foam: Memory foam mattresses use conforming viscoelastic foam over firmer polyurethane base foam. Some innerspring mattresses have memory foam in their upholstery layer. Different feels and comfort levels are achieved by varying the thickness, weight and formulation of the viscoelastic foams and the base foams. Latex and memory foam mattresses each provide a unique feel. This type of mattress is good at relieving pressure on painful joints. Many memory foam mattresses are more expensive than standard spring mattresses. Memory foam is affected by temperature. In a cool bedroom, a memory foam mattress will feel firmer than it does in a warm bedroom. Memory softens and conforms to the sleeper in response to body temperature and body weight. Traditional memory foam molds to the body creating a depression the sleeper must roll out of when changing sleep positions. Mattress manufacturers have responded to this issue by using “faster response” memory foams. They spring back more quickly when the sleeper moves. Foam mattresses are also known to generally “sleep warmer” than innerspring mattresses. Mattress makers have addressed the issue with “open-cell” memory foams, pinhole cored memory foam, gel-infused memory foams, channel-cut foam cores, reticulated foam support layers and other technologies to improve air circulation through all-foam beds.
- High density foam: Similar to memory foam mattresses, a high density foam mattress uses a more compact foam typically made from polyurethane. This kind of foam is made largely from open cells that are packed together tightly. High density foam mattresses offer comfort and longevity because they are more dense than a traditional foam mattress. High density foam mattresses that have an innerspring system last even longer and eliminate mattress sagging.
Mattresses can also be made from bladders of some fluid, notably water or air. These date to antiquity – goatskin bladders filled with water were used in Persia at least as early as 3600 BCE – and gained increased popularity in the 20th century with improved manufacturing.
- Air mattress: Air mattresses use one or more air chambers instead of springs to provide support. Quality and price can range from inexpensive ones used occasionally for camping, to high-end luxury beds. Air mattresses designed for typical bedroom use cost about the same as inner-spring mattresses with comparable features. Air bladder construction varies from a simple polyethylene bag to internally baffled, multiple chambers of latex (vulcanized rubber) or vinyl with bonded cotton exteriors. Mattresses may have a layer of foam above the air chambers for added cushioning, and may be enclosed in a cover. Some such beds are termed soft-sided air beds. Permanent use adjustable-firmness “airbeds” became popular particularly after market leader Select Comfort began a major marketing campaign around 2001. The original airbed was manufactured by Comfortaire in 1981, which was later purchased by Select Comfort. There are several other manufacturers. Some allow independent adjustment of each side of the bed. They are made in a variety of models from basic, no-frills ones that measure about 7″ in height, to high-profile, 15″ tall hybrids that contain several types of foam, pillow tops, and digital pumps with memory for individual pressure settings. Studies suggest that adjustable-firmness beds are better for back pain. Adjustable-firmness mattresses for medical use have special control mechanisms. In the 1990s self-adjusting air beds that automatically change their pressure periodically, or inflate and deflate several air chambers alternately, were introduced. The intention of these periodic changes is to reduce problems with decubitus ulcers (bed sores), though as of 2008 the effectiveness of these techniques was still being researched. Air mattresses for camping are available which are filled with foam which itself provides little support, but expands when the air valve is opened allowing air to enter, so the mattress (nearly) inflates by itself. This is especially useful for campers who carry their equipment as, unlike with normal air mattresses, no pump is needed for inflating. Available brands include Aerobed, Coleman, Therm-a-Rest and others. The U.S. Consumer Product Safety Commission advises consumers not to let infants sleep on air mattresses. This is motivated by reports of deaths, mostly infants younger than 8 months of age, who were placed to sleep on air mattresses, and either suffocated in a face down position on an air mattress or died due to suffocation after falling into gaps between the mattress and bed frame, or the mattress and adjacent furniture or wall.
- Waterbeds: A waterbed is a mattress with water in its interior instead of metal coils or air. Waterbeds can be lined with different layers of fiber to achieve the level of firmness the user desires. Waterbeds are well known for providing support to the spine and other body parts, similar to the other mattress types. There are several options of support which range up to 100% waveless, where the user does not notice that they are lying upon a waterbed.