Open Coil is the most common type of springing. There are usually approximately 350 springs in a 5’0” King-size mattress. The springs are positioned in rows and joined to each other at the top and bottom with a spiral helical wire or mesh. They come in a variety of tensions, each of which gives the mattress a different feel. This type of mattress is generally priced from budget to mid range.
Most Open Coil mattresses are of medium to firm feel. A softer or firmer mattress can be made by using different thicknesses of wire. Where you see the term “gauge”, this relates to the thickness of the wire used to make the spring – the lower the number, the thicker the wire and the firmer the feel, so a 12.5 gauge will be a firmer mattress than a 13.5 gauge.
A wide variety of fillings are used in interior sprung mattresses, such as coir fibre, foam, cotton, polyester, wool and hair. At the luxury end of the market, silk, mohair and cashmere or memory are often added. The quality and quantity of filling also affects the level of comfort and, of course, the price.