What is the Shore Hardness Scale - Industrial Physics What is the Shore Hardness Scale - Industrial Physics

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The Shore Hardness Scale Explained

The Shore Hardness Scale Explained

The Shore hardness scale is a method of determining the hardness or flexibility of a variety of materials. It’s been around a long time and is commonly used in a whole range of industries. Want to know more about how it could be part of your QA process? Dive on in for everything you need to know about the Shore hardness scale and material testing.  

What is the Shore hardness scale? 

When talking about the Shore hardness scale, we’re actually talking about a series of different scales designed for measuring the solidity of a variety of materials. It was invented by Albert Ferdinand Shore in the 1920s and remains a reliable testing method today. Shore created the scale to allow for the determination of a variety of materials, allowing for a common point of reference when talking about the relative hardness of materials.  

What does the Shore hardness scale typically test? 

The Shore hardness scale is commonly used to test the hardness of soft rubbers, rigid plastics and supersoft gels. Shore hardness is tested with an instrument called a Durometer, which has a foot that is inserted into the material being tested. The foot is spring loaded and it is the spring that propels the penetration.  

The penetration of the indenter foot and the amount of time penetration takes is used to determine the hardness of the material. 

How units of Shore hardness are expressed

The number on the instrument indicates the material’s resistance to indentation. The higher the number, the more resistant the material is, so a low number indicates a softer material, and a high number indicates a harder one. Shore hardness is expressed as a number followed by either the letter A or D. The letter is determined by which scale is being used to test the material. 

The different Shore hardness scales 

There are a range of Shore hardness scales, including Shore A, Shore D, Shore H and Shore O. Shore A and Shore D are most commonly used in the rubber and plastics industry.  

Shore A scale

Commonly used for softer plastics, like polyolefins, fluoropolymers, and types of vinyl. It is suitable measuring the hardness of softer, more flexible materials, ranging from the soft gel like materials that measure at Shore A 0 all the way to semi-rigid plastics that measure around the 90-95A end of the scale.  

Shore D scale

Commonly used for harder rubbers and thermoplastic elastomers. There is some crossover between the two scales and typically materials softer than 50D (approximately equivalent to 95A) are expressed using the A scale even though they could also be measured on the D scale. After 65D, materials are rigid and inflexible. Once you get to the end of the D scale, it is common to transition in Rockwell Hardness Testing for materials like Nylons and Acetals. 

Approximate hardness by scale

 Extra soft Soft  Medium soft Medium hard  Hard Extra hard  
Shore A 0 10-30 30-60 60-80 80-100  
Shore D    0-30 30-60 60-100 


Shore A scale tester

If you’re looking for a Shore hardness tester for Shore A scale, then we recommend our TQC Shore Hardness Gauge. This compact, handheld gauge is suitable for materials like materials such as elastomers, vinyl, rubber, leather, PVC, silicone-rubber, Teflon, neoprene and more. It can also be used to test to a variety of important industry standard specifications, including ASTM D2240, DIN 53505 and ISO 868. 

The Shore scale as part of a testing suite 

The Shore hardness scale offers a useful method for testing the hardness of plastics, rubbers, and polymers but it is only one part of a good QA process. It isn’t a suitable indicator for other properties, such as strength or resistant to abrasion, wear or scratches. Our experts can help you discover the tools for a testing process that will match your needs, whatever industry you’re in.   

TQC Sheen at Industrial Physics

As a global test and inspect expert, Industrial Physics is the perfect partner for all of your testing solutions. Our specialist testing brand TQC Sheen includes a huge range of testing products, including everything you need to test rubbers, paints, and coatings.  

Our expert team is always on hand to help you grow your testing capabilities or keep your machines in top shape, whether you need your machines serviced or training on how to operate them. Find out more about TQC Sheen products.