Joint Industry Foam Standards and Guidelines Published: 7/94
INDENTATION FORCE DEFLECTION (IFD) STANDARDS AND GUIDELINES
4.1 To the furniture manufacturer and final user of a piece of furniture, one of the most important quality questions is related to the firmness of the seat cushions. The firmness of a polyurethane foam cushion is measured by a physical property called the indentation force deflection (IFD).
4.1.1 The history of describing firmness is very interesting. Prior to the advent of polyurethane foams, rubber latex foams were in wide use for furniture cushions. The term used to describe the firmness or softness of foam rubber was RMA, which stood for Rubber Manufacturers
Association. RMA was measured only slightly different from the way IFD is measured today.
4.1.2 When polyurethane foams arrived on the scene, they weren't associated with the rubber industry, so the acronym "ILD" was developed. "ILD" stood for "indentation load deflection." During the drive for conversion to the metric system in the late seventies, the American
Society of Testing and Materials (ASTM) decided that in all of their publications and test methods, the metric system would be used. Because the ASTM insisted on the use of the word "force" rather than "load," the term "IFD" came into common use--replacing "ILD." IFD stands for "Indentation Force Deflection and the actual test method is basically identical to the older ILD test.
4.2 It should be noted that the foam IFD is only one of the contributors to the comfort of a furniture seat cushion. There are many other contributors, and some of these have already been discussed.
4.2.1 In this publication, The Joint Industry Committee has purposely avoided using the word "comfort" directly associated with IFD or IFD properties. Suffice to say, IFD is a part of the comfort equation, but IFD is not always related directly to comfort. For example, one cannot say that a 25% IFD of 26 lbs/50 in2 always produces comfort, while a 25% IFD of 40 lbs/50 in2 does not produce a comfortable seat. Comfort is not directly related to the magnitude of the IFD number alone.
4.2.2 IFD is defined as the amount of force, in pounds, required to indent a fifty square inch, round indentor foot into a predefined foam specimen a certain percentage of the specimen's total thickness. IFD should always be specified as a number of pounds at a specific deflection
percentage on a specific height foam sample, e.g.., 25 pounds/50 in sq. at a 25% deflection on a four inch thick piece. Different IFD values will be obtained if a different percentage deflection is used or if the height of the test specimen is different. It is also necessary to report the entire sample size. Sample size, in addition to thickness, can drastically influence IFD readings. Flexible polyurethane foams can be made in a very wide range of IFD's. To get a good feeling of the potential uses of each of the various IFD ranges, the following chart should be of some assistance:
IFD @25% DEFLECTION USE (pounds/50 in sq. on 20 "x 20"x 4")
6--12--------------Bed pillows, thick back pillows
12-18--------------back pillows, upholstery padding, wraps
18-24--------------thin back pillows, tufting matrix, very thick seat cushions, wraps
24-30--------------average seat cushions, upholstery padding, tight seats, certain mattress types, quilting
30-36--------------firmer seat cushions, mattresses
36-45--------------thin seat cushioning and firm mattresses
45 and up----------shock absorbing foams, packaging foams, carpet pads, and other uses requiring ultra-firm foams.
The above table should only be used as a beginning guideline. The actual IFD required is a function of many things, such as the design type, spring type used, and other parameters within the actual furniture construction.
4.3 IFD varies significantly with foam thickness. On the exact same foam, the IFD increases as the thickness increases, as the following chart illustrates:
Foundation: performs the same function as a box spring, but a foundation is a rigid support.
Futon: is a bendable, foldable mattress that will fit into an upright frame. When the frame is upright, it is used as a couch. It is usually used as a couch during the day and a bed at night. Futons vary widely in price. A frame and mattress and cover can range from $200 - $1000 and higher. These days some futons are very comfortable, unlike most of those made prior to
year 2000.
Hi-Density Foam: Foam measured with a density greater than 1.8.
Hi-Resiliency Foam: Also called HR Foam is foam with a density greater than 1.8.
IFD: Indentation Force Deflection (IFD) is a measurement of foam firmness. Firmness is independent of foam density, although it is often thought that higher density foams are firmer. It is possible to have high-density foams that are soft or low-density foams that are firm, depending on the IFD specification. IFD specification relates to comfort. It is a measurement
of the surface feel of the foam. IFD is measured by indenting (compressing) a foam sample 25 percent of its original height. The amount of force (in pounds) required to indent the foam is its 25 percent IFD measurement. The more force required, the firmer the foam. Flexible foam IFD measurements range from 10 pounds (supersoft) to about 80 pounds (very firm).
