Indentation force-deflection is a process used in the flexible foam manufacturing industry to assess the "softness" of a sample of foam such as memory foam. To conduct an IFD test, a circular flat indenter with a surface area of 323 square centimeters (50 sq. inches - 8" in diameter) is pressed against a foam sample usually 100 mm thick and with an area of 500 mm by 500 mm (ASTM standard D3574). The foam sample is first placed on a flat table perforated with holes to allow the passage of air. It is then "warmed up" by being compressed twice to 75% "strain", and then allowed to recover for six minutes. The force is measured 60 seconds after achieving 25% indentation with the indenter. Lower scores correspond with less firmness; higher scores with greater firmness. US measurements are given in pounds-force, and European ones are given in newtons.
- ^ Nigel Mills (23 March 2007). Polymer Foams Handbook: Engineering and Biomechanics Applications and Design Guide. Butterworth-Heinemann. p. 217. ISBN 978-0-08-047544-8.
- ^ Kurt C. Frisch; Daniel Klempner (6 August 1998). Advances in Urethane: Science & Technology. CRC. p. 10. ISBN 978-1-56676-675-3.
- Joint Industry Foam Standards And Guidelines https://www.pfa.org/industry-standards/