2a. How to measure it?
One method to measure hardness of a mattress is by using the standard ISO 2439 method, which states that the ILD-hardness (Indentation Load Deflection) measures the pressure that is required to load the mattress core till 25%, 40% or 60% compared to its original thickness with a circular plate of 50 square inches or 322 cm².
The other method to measure hardness is by using the CLD-hardness (Compression Load Deflection) which is in accordance to the standard ISO 3386, Latexco Belgium, where most of our European Bedding latex cores are manufactured, uses this method which is the counter pressure (= force per surface) in Pascal when 25% of the mattress core is pressed in with the same circular plate. Take note that 1 kPa (kilopascal) equals 10 g/cm² (gram per square cm).,