If you take the sheets off your bed and look at your bare mattress, you probably won’t see much. On the outside, all you see is the ticking. Ticking is the outermost layer of the mattress and is usually composed of polyester, cotton-polyester blend, wool, vinyl, or silk. Vinyl ticking is water resistant, but can get very hot and tends to stretch and sag.
It is often mentioned that silk makes a mattress cover cooler and water resistant. Neither are true, but it does add a nice lustrious look to the bed. Wool fibers are firmer in consistency and do not stretch, but those same traits can make a cover appear more lustrious looking. They are thicker fibers and do not breath as well or wick away moisture like cotton can. The firmness of wool fibers will add firmness to the layer below the cover, but also not allow the body to sink in as deep, thus preventing the increase heat that comes from being enveloped by the material of the cover. Cotton and polyester-cotton blends fall into two categories; stretchable and non-stretchable. The more cotton fibers in the cover, the more breathable the cover becomes and the better it can wick away moisture. Also, jersey, velour, and terry cotton type covers will have the most stretch.
Manufactures began to use stretchable covers to allow the bed to conform better to the individual when a conforming foam such as visco-elastic memory foam was used on the top layer of the mattress. Any material can be quilted by stitching fiber fill pockets for added surface softness. What is important to note about quilted stitching is that, as with any stitching, the stitches should be uniform and unbroken to guard against loosening and puckering.