The vast majority of all mattresses sold today are innerspring mattresses, including some of the best known brands in the industry — like Serta, Jamison, Spring Air, Sealy and Kingsdown Mattresses — so there are many excellent choices in this category. Innerspring mattresses employ one of five coil systems. Continuous coil systems, which provide excellent strength, are made from a single length of steel wire woven throughout the system. The Karr system features hour-glass shaped coils with the end left unknotted so that each coil moves independently to minimize sagging.
The Marshall innerspring mattress system uses very light wire, resulting in more coils per mattress and more even weight distribution. Stearns and Foster’s knotted Bonnel innerspring mattress features hour-glass shaped coils wrapped with knotted ends around the top and bottom. The offset coil system replaces the bottom portions of the wire coils with flat sides which facilitate better hinging action when placed within a spring unit. The open end offset coil, found in both Spring Air and Sealy innerspring mattresses, utilizes an extra “turn” of working wire to produce greater spring action on each end for more contoured and comfortable support.
Coils are usually tempered to ensure long-lasting springiness for many years. Plastic coating on the coils also promotes durability. Coils made with thicker-diameter wire (measured in gauge number) provide greater support and durability. The number of coils is not necessarily a quality indicator as coil size is also a factor. Higher gauge numbers indicate relatively thinner wire. Top-grade mattresses usually use 13 gauge wire. Today’s innerspring mattresses usually feature a soft top layer, about 1 to 4 inches thick This top layer can consist of a quilted fabric or a pad of latex or memory foam.
