The softness or firmness of your favourite couch or easy chair is due in large part to the type of upholstery foam used in the construction of the furniture. Knowing about the different types of upholstery foam will make it easier to ask questions when you start browsing for new furniture or are reviewing your options for recovering your current furniture.
Soft to Firm
Ask about the compression measurement of the foam. Polyurethane foam is used for upholstery and the firmness, or compression measurement, of polyurethane is determined by the amount of pressure needed to press the foam down to 1/4 of its height. The test to measure compression may also be referred to as the indentation load deflection or ILD. The higher the compression measurement, the more firm the foam will be. For seat cushions, look for a 24 to 30 rating for average firmness or 30 to 36 for more firmness.
The quality of polyurethane is determined by the weight of 1 cubic foot of the foam. The weight of the foam is indicative of its density. The density level of the best quality foam will be between 1.8 and 3.2, though that rating may appear, for example, as #21 instead of 2.1. The better the foam quality, the longer it will last and spring back. For seat cushions, look for 2.5 or higher for the density rating.
It does not matter if you have cigarette smokers in the house or not, ask if the foam has been rated "fire resistant (FR)." Fire resistant foam can reduce the potential of the foam igniting from a smoker's dropped ashes but also sparks from a fireplace or a candle that tips over. An HR rating may be included with the FR rating. HR stands for "high resilient," which means the foam will last longer, an important factor if the foam is in a location that sees lots of use.
Open or Closed Cells
Polyurethane foam is comprised of cells. The cells can be open or closed. Open cells are the most common and refer to cells that open into the neighbouring cell. Closed cells do not open to the neighbouring cells, allowing that type of foam to float longer. You would want to use closed cell foam to upholster seat cushions for a boat.
Shape and Size
Upholstery foam can be cut into any size needed or pieces can be glued together. It is easier to glue open cell foam. In addition to cutting seat cushions to exact specifications, upholstery foam can be cut in triangular (wedge) or circular pillars to use as bolsters, disc shapes or small rectangles or squares to use for pillows, baby, dog or camper mattresses, or thin sheets to pad furniture arms, valances or walls that will be covered with fabric, such as for a home theatre.