Definition of Hardness

Meaning of the Term as it Pertains to Mattresses

What is Hardness?

Hardness is a broadly used term that can describe mattress support or comfort level. When describing support, hardness refers to a mattress's load-bearing capabilities. The term mainly applies to foam mattress support because foams that take more force to compact feel harder. When excess weight is applied, softer foam mattresses bottom out more quickly than hard foam mattresses. Though the term is often used generally, hardness can be judged empirically through indention load deflection, or ILD. In regard to support, hardness is simply a reflection of a mattress's ability to provide consistent performance when a certain amount of weight is applied. Hardness does not reflect quality.

When used to describe comfort level, hardness refers to the initial feel of a mattress. Shoppers often call firm mattresses hard and plush mattresses soft. Though hardness is commonly used to refer to support and comfort level, shoppers should remember that the two do not affect one another.

Hardness Loss

The weakening of foam in a mattress. Hardness loss reflects mattress durability and longevity. Mattress foam can gradually soften throughout the night, which causes support to diminish. After a night of use, foam typically recovers most of the initial hardness. However, foam flexibility can gradually decrease over time, which can cause mattresses to experience significant hardness loss. Cheaper quality mattresses can experience substantial hardness loss in just a few months.

Like hardness, hardness loss can be measured through compression testing. Foam density is not directly correlated with hardness loss and durability, but higher-density foam tends to experience less hardness loss. High-quality foam mattresses use resilient foam materials with durable cell structures and experience minimal hardness loss. As a result, the mattresses tend to last for upwards of 15 years.