Our most popular mattress! Our CozyPure natural latex rubber mattresses create an ideal sleep system that reacts to your body with dynamic distribution of weight. They feature instant-recovery bounce-back, and offer superior support where you need it, while gently yeilding softness to other areas of the body. Our CozyPure natural latex does not have harmful chemicals, it's moisture regulating so you won't "sleep hot", the surface comfort provides proper spinal alignment yet delivers the perfect balance of pressure-point relief... and it's environmentally-safe. No wonder it's our customers favorite mattress choice!

Quality and testing - Physical tests The fundamental question is which tests are and which are not relevant to the comfort of a mattress core, i.e. to the body support and the durability. Tensile strength and elongation under conditions of breaking are of no relevance, as a mattress core under circumstances of normal use is merely loaded by pressure and not by tearing.

Hardness The hardness is the resistance against pressure. The hardness and the density (mass per unit volume) of a latex rubber foam mattress core are interrelated. As the density decreases, a growing loss in hardness arises after repeated loading.

2 Methods:
1 Standard ISO 2439 states that the ILD-hardness (Indentation Load Deflection) equals the force 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.
2 Our supplier uses the CLD-hardness (Compression Load Deflection) according to standard ISO 3386, which is the counterpressure (= force per surface) in Pascal when 25% of the mattress core is pressed in with the same stamp. Notice that 1 kPA (kilopascal) equals 10 g/cm² (gram per square centimeter).

Sag factor
What is even more important to comfort is that the mattress core feels soft and increasingly shows resistance as the core is further depressed. The quality "to react as equally as possible to a pressure or a load" is called the sag factor. This sag factor is presented through the ISO 2439 standard as the ratio of 65% ILD to 25%. The higher this index, the better the latex supports the body equally. The sag factor for regular PU-foams is about 2 and for the more resilient HR-foams (High Resilient) about 3. Latex foam performs obviously better with a sag factor up to 4!

Resilience
Resilience or elasticity is measured by the "ball-rebound"-test (ASTM D3574). In this test, a steel ball is dropped from a certain height on the foam en afterwards the rebound is measured in % compared to the predetermined height. The resilience of regular PU-foams is situated between 40 and 50 %. HR-foams have an elasticity of 50 to 60% and latex foams of 60 to 70%.

Durability (fatigue)
It is important that the hardness and the resilience of the foam should be preserved over a longer period of intensive use. The durability can be tested in 2 ways: a static fatigue test compresses the foam during a period of time under demanding circumstances. During a dynamic fatigue test the foam is repeatedly compressed to imitate the load bearing during a normal life span (10 years).

1 The compression set is determined by ISO 1856 by compressing a foam sample 75% during 22 hours under a temperature of 70°C and then calculate the loss in height in terms of percentage. Good foams lose height less then 15%. A more relevant test however is the dynamic fatigue test. This test, according to ISO 3385 standard, loads a foam sample of 40 by 40 cm 80 000 times with a weight of 75 kg (a force of 750 N). Afterwards, the loss in height and in hardness is determined in terms of percentage compared to the original value.

Another dynamic fatigue test is done according to the testing method of EN 1957 (ecolabel directive 98/634/EG). In this test, a roller-shear with predetermined dimensions and a weight of 140 kg is rolled 30 000 times up and down the mattress. Afterwards the thickness and the hardness after 100 cycles are compared to the end results. The hardness is determined as the average incline at 210 N, 275 N and 340 N in the load deformation curve. Tests run by the German Institute LGA in 1997 following the project EN 1957 gave results of about 3 mm loss in thickness and 3 % loss in hardness for a latex mattress core.

Hysteresis
The hysteresis can be determined by measuring the " banana " curve via loading and de-loading of a mattress. The load deformation curve is measured by means of a circular plate op 355mm diameter, that gradually builds a force up to 1000 Newton, during which the loading is observed at the same time.

The hysteresis is calculated by dividing the surface between load and de-load curve by the load surface. (expressed in %). The hysteresis indicates the amount of energy that is absorbed by a latex core during loading / de-loading. The higher the absorption of energy by a mattress , the more muscle strength (energy) the person asleep will need to change its position and the lower the quality of his sleep. Mattress cores which are too hard however have a too low hysteresis, which results in no energy being absorbed by the mattress and the person sleeping 'above' the mattress. This also excludes a stable body position. A ideal hysteresis lies between 20 and 30% when the hardness is comfortable.The LGA-test mentioned earlier gave a hysteresis of 20,3% with a hardness of 6,83N/mm according to EN 1957.