HOW IS MEMORY FOAM AND POLYURETHANE FOAM GRADED?
For material to be visco-elastic, it has to be temperature sensituve and have the qualities to rebound fairly quickly and return to its normal shape. Memory Foam is graded by its visco-elastic nature and its durability by breaking it down into the following grading system:WEIGHT OF THE MEMORY FOAM MATTRESS (density in pounds per square foot): The weight of the memory foam is determined by the amount of chemicals used. The more chemicals, the higher the density and the more visco-elastic the memory foam will become. The density will not determine the hardness of the material, this is measure by the ILD rating (see below). Many memory foam mattresses use anywhere from a 3lb foam to a 5lb foam density. From our experience, anything less than 3 lbs will generally not qualify as visco elastic memory foam and not offer the same therapeutic qualities. ILD RATING (Indentation Load Deflection) OF THE MEMORY FOAM MATTRESS: The ILD rating measures how hard or soft a memory foam material is. A 25%
