Correctly Interpreting Shore Hardness Values

What do Shore hardness values mean – and how should they be interpreted correctly?

For many elastic and also rigid plastics, a Shore hardness value can be found in the material data, for example Shore A 70 or Shore D 60. However, for many users it is not immediately clear what exactly lies behind these numbers – and what they specifically mean for the part they request or order from PROTIQ.

Shore hardness describes the indentation hardness of a material. It is measured using a standardized testing device known as a durometer, which is pressed against the material surface with a defined force. The more the material can be indented, the lower the measured Shore value. Conversely, the less the material deforms, the higher the value.

One thing is particularly important here: Shore hardness is not a quality indicator. Rather, it serves as an orientation value to make materials comparable in terms of their perceived “hardness or softness.”

Why there are different Shore scales

Because very soft elastomers and rigid plastics cannot be meaningfully measured using the same test method, different Shore scales exist. Which scale is used depends on the hardness range in which a material lies. In industrial environments, Shore 00, Shore A, and Shore D are particularly relevant.

The accompanying diagram shows these scales side by side and illustrates how different materials can be positioned along a spectrum from very soft to very hard.

Shore 00 – for very soft, highly compliant materials

Typical for: very soft elastomers, foam-like or gel-like plastics

Comparable to: gummy bears, silicone gel, very soft damping elements

Applications: damping, protection, comfort or grip areas

A rough guideline for classification:

•  •  Shore 00 ~10 → extremely soft, hardly any dimensional stability
•  •  Shore 00 ~30 → highly elastic and easily indentable
•  •  Shore 00 ~50 → soft, but with noticeable resistance

The Shore 00 scale is used whenever a material is so soft that differences can no longer be meaningfully represented using Shore A.

Shore A – for elastic rubber materials

Typical for: rubbers, TPU, flexible plastics

Comparable to: seals, rubber bands, tire compounds

Applications: seals, flexible components, grips, bellows

A rough guideline for classification:

•  •  Shore A ~40 → very soft, highly flexible
•  •  Shore A ~70 → classic “rubber hardness”
•  •  Shore A ~90 → very stiff, hardly indentable

Shore A is the most commonly used scale for elastic materials and covers a wide range between soft and firm.

Shore D – for rigid plastics

Typical for: hard, largely rigid plastics

Comparable to: technical housings, robust design or functional parts

Applications: structural components, mechanically stressed parts

A rough guideline for classification:

•  •  Shore D ~30 → still slightly compliant
•  •  Shore D ~60 → clearly hard and dimensionally stable
•  •  Shore D ~80 → very hard, hardly any elasticity
  

Shore D is used wherever elastic behavior plays only a minor role and stiffness and dimensional stability are the primary focus.

What Shore hardness indicates – and what it does not

Shore hardness is very well suited for classifying materials in terms of feel and functional behavior. However, it does not provide information about many other important properties. Factors such as tensile strength, elongation at break, recovery behavior, abrasion resistance, temperature resistance, or performance under continuous load cannot be derived from Shore hardness alone.

This point is particularly important in 3D printing, as component geometry, process parameters, and material structure can have a significant influence on the actual behavior of the part.

Why we specify Shore hardness values at PROTIQ

At PROTIQ, we specify Shore hardness values for some materials to provide an initial, realistic orientation. They help compare materials and better assess expectations regarding flexibility or stiffness. At the same time, they do not replace an application-specific evaluation.

Our tip: Use Shore hardness as a starting point for material selection. For functional or demanding applications, it is worth considering the complete property profile or seeking individual consultation.