What Is Shore A?
The Shore A hardness test is a method in which hardness is determined by pressing a spring-loaded indenter into the specimen surface and reading the indentation depth on a 0–100 scale. It is defined for soft elastomers.
Purpose of Shore A
The purpose is to quickly check the hardness of rubber and elastomer components, verifying formulation and cure consistency.
Which Products Is Shore A Applied To?
- Rubber gaskets and seals
- Elastomer hose and section
- Soft plastic parts
- Shoe soles
- Silicone components
In Which Sectors Is Shore A Used?
Standards Related to Shore A
- ISO 868
- ASTM D2240
- ISO 7619-1
Shore A Conditions
- Durometer type
- Shore A (soft elastomers)
- Reading time
- Defined in the standard; typically 3 s or an instantaneous reading
- Specimen thickness
- At least 6 mm; layers are stacked if necessary
- Environment
- 23 °C ± 2 °C
Equipment for Shore A
- Shore A durometer
- Fixed-loading stand
- Thickness gauge
- Reference calibration blocks
Sample Requirements for Shore A
- Thickness must be at least 6 mm
- The surface must be flat, clean and fully cured
- Measurement points must be at least 12 mm from the edge
- Generally five measurements are taken and the median or average is given
Duration of Shore A
The measurement takes a few seconds; a specimen set is completed quickly.
Shore A Procedure
- 1Specimen thickness is measured and conditioning is completed.
- 2The durometer is verified with a reference block.
- 3The indenter is pressed perpendicular to the surface with a fixed load.
- 4The value is read at the defined time.
- 5The measurement is repeated at different points and the result is reported.
Shore A Acceptance Criteria
The acceptance range is given in the product specification as a Shore A value and tolerance (e.g. 70 ± 5 Shore A).
Evaluation of Results
The scatter of the measurements is evaluated. In thin specimens the effect of the underlying surface raises the result, which is why the thickness requirement is critical.
Shore A Report
- Standard applied
- Durometer type and reading time
- Specimen thickness and ambient temperature
- Individual measurements and the result
Accreditation
EUROLAB holds internationally recognised accreditation obtained from accreditation bodies party to the IAF and ILAC multilateral recognition arrangements, under ISO/IEC 17025 for laboratory testing, ISO/IEC 17020 for inspection and surveillance, and ISO/IEC 17021-1 and ISO/IEC 17065 for system and product certification. This chain ensures the reports and certificates issued are accepted worldwide.
Whether this test can be offered within accredited scope depends on your product and the standard applied; since accreditation is method-based, the scope is confirmed in writing at the quotation stage.
Scope and authorisationsRelated Regulations
- Rubber and elastomer product specifications
Mekanik Testler — What Does This Testing Field Cover?
The section below describes the field that the Shore A test belongs to; the conditions and acceptance criteria of this particular test are given in the sections above. The scope specific to your product is confirmed in writing at the quotation stage.
Mechanical testing measures how a material or a part behaves under force. The family ranges from static loading (tension, compression, bending) to time-dependent behaviour (fatigue, creep), and from hardness and wear to fracture toughness.
What these tests have in common is that the result is reported as a MATERIAL PROPERTY. Yield strength or hardness is not a conformity decision; it is numerical data against which the design and the product standard will compare. Mechanical test reports are therefore usually an input to an engineering decision rather than to a product approval — material selection, safety factor, life prediction.
The distinction between static and dynamic behaviour is the key to understanding the field. A part may appear entirely unstressed under a static load yet break under repeated loading; fatigue fracture occurs at stresses well below the yield strength and gives no warning. For rotating, vibrating or cyclically loaded parts, a tensile test alone is therefore not sufficient evidence.
Test conditions determine the result, and this is critical for the readability of the report: specimen geometry, loading rate, temperature, conditioning and the gripping arrangement. The same material gives different values under different conditions. In plastics the rate effect is very pronounced, in metals the temperature effect; in composites the specimen orientation changes the result entirely.
Hardness is the most misused measurement in the field. Because it is fast, close to non-destructive and inexpensive, it is often used in place of strength. Conversion tables from hardness to strength exist, but they are APPROXIMATE and depend on the material group; using them as the sole evidence in material acceptance is wrong.
The fracture mechanics side requires a specific competence. Fracture toughness and fatigue crack growth rate measurements make it possible to calculate how long a cracked structure will last; they are the basis of damage-tolerant design in fields such as pressure equipment, aircraft structures and pipelines.
Method groups in this field
Static tests
Tension, compression, bending, shear and torsion. Yield and tensile strength, elongation and modulus of elasticity are obtained.
Impact tests
Charpy and Izod notch impact; the brittle-to-ductile transition behaviour of the material is determined as a function of temperature.
Hardness
Brinell, Vickers, Rockwell, Shore and micro hardness. Valuable for surface treatment depth and local differences in strength.
Fatigue
Force- and strain-controlled axial fatigue, fatigue in bending; S-N curves and the endurance limit.
Creep and stress relaxation
Behaviour under long-term load at high temperature; decisive for boiler, turbine and pressure equipment materials.
Fracture mechanics
Plane-strain fracture toughness, the J integral, CTOD and fatigue crack growth rate.
Wear and friction
Taber and rotating drum abrasion, coefficient of friction measurements.
Commonly confused in this field
- Calculating strength from hardness is approximate; it cannot be used as the sole evidence in material acceptance.
- Adequate static strength does not demonstrate fatigue strength; a cyclically loaded part requires a separate test.
- If test rate and temperature are not reported, the result cannot be compared — especially for polymers and composites.
- A test specimen and the actual part may not give the same value; moulding orientation, weld lines and differences in surface treatment all have an effect.
- A strength value given for a composite without stating the specimen orientation is meaningless.
- ASTM and ISO counterparts measure the same quantity but use different specimen geometries; the results are not treated as directly equivalent.
Which decisions these results support
- Design verification and material selection
- Incoming material control and supplier approval
- Meeting the mechanical requirements of the product standard
- Failure analysis, life prediction and damage tolerance calculation
- Verifying heat treatment and surface treatment processes
Related Tests
Frequently Asked Questions About Shore A
What is the difference between Shore A and Shore D?
Shore A is defined for soft elastomers, while Shore D is defined for hard plastics and hard rubbers. Indenter geometry and spring force differ; values cannot be converted between the two.