4. What is the difference between ILD and kPa?
ILD or Indentation Load Deflection is one measure of load bearing and is expressed in pounds per 50 square inches at a given percentage deflection of the foam (normally 25%).
To obtain the value, a 50 square inch circular plate is pushed into the foam surface, stopping at a given deflection and reading the load.
For example a 25 percent ILD of 30 means that it takes 30 pounds load to compress a 4 inch thick piece of foam to a 3 inch thickness. So, an ILD standard 34 and 37 (pounds) equals the hardness of 4.8 and 5.2 kPa, given 0.4536 kilogram per pound and 322.58 square centimeters for the
50 square inch stamp.
Formula : 1 ILD = 0.14 Kpa or 1 Kpa = 7.14 ILD
ILD is used in countries which use the old English system. However, kPa, the metric system - an internationally agreed system of measurement, is now used in almost every country in the world.