Shore Hardness Testing for Rubber, Plastic, and Foam Materials
The Shore® Instrument Company has developed a wide range of instruments for the testing of the hardness of rubber, plastic, thermal plastics (TPE), and rigid plastics. These instruments are used in every industry to measure the materials that make up tires, golf balls, footwear, and printer rollers, as well as industrial rubber and plastic products. They conform to all ASTM and international standards for measuring hardness, such as ASTM D 2240, DIN 53 505, ISO 7619 Part 1, and JIS K 6253. The instrument, known as the durometer (pictured left), has an indenter with an accurately calibrated spring.
When fully extended in the relaxed position the durometer gauge is at zero (0). Hardness value is determined by pressing the gauge onto a sample of defined thickness. The penetration of the indenter and spring move the gauge from zero upward based on the amount of penetration. The lower the number, the softer the material. The highest value is always 100.
Durometer is normally allowed a tolerance of +/-5. That is, if a compound is said to be 40 durometer on the Shore A scale, then any tested batch could be between 35 and 45 durometer and still be acceptable as 40 durometer. Tighter tolerances can be held when required.
Durometer Scales
There are a variety of durometer scales since elastomeric and plastic resins vary over a wider range than one scale can accommodate. Durometer is measured on a scale of Shore hardness. The different Shore types listed below dictate the shape and size of the indenter that is pressed into the material to determine the hardness. Shore type is chosen by the material classification and general hardness of the material.
- Shore A – Industrial rubber products and compounds
- Shore D – Hard plastics and for some very hard rubber compounds
- The Shore 00 – Sponge rubber and plastic foams
Use the form on the right to download our durometer chart to show you how these three scales overlap.
It’s also not uncommon for hardness to be inaccurately confused with a few other physical properties of rubber, plastic, and foam materials. Click here to learn more about these common misconceptions.
Marian converts foam and sponge materials of different density, thickness, hardness, and composition. We are proud to say our sales engineers have an average of 15 years of experience working with foam and sponge materials. This wealth of knowledge enables our team to understand the various different physical attributes of the materials, including Durometer. When in doubt, contact Marian Sales Engineers for help with material recommendations and rapid samples.
Download Durometer Chart
For exact measurements, fill out the form below.