Shore Hardness

Shore Hardness (DIN 53505)

A needle is pressed into the specimen against a spring force.
The resistance to this penetration (in %) is the measure of the Shore hardness.
An extremely soft material (Shore 0) would not offer any resistance to the needle.
At 100 Shore, the needle cannot penetrate the material at all.

Shore A: needle with rounded end (for soft materials such as rubber)
Shore D: needle with a sharp end (for hard materials such as plastic)