🔩 Shore hardness of plastics and ebonite — durometer type A (softer materials) and type D (harder), reading after 15 s or instantaneous, mean of five measurements; PN-EN ISO 868:2005 (ISO 868:2003)

Materials and NDT PN-EN ISO 868

Overview

WHAT THE STANDARD COVERS. Scope from the PKN card of PN-EN ISO 868:2005, in full (our translation): "A method is described for determining the indentation hardness of plastics and ebonite using durometers of two types: type A used for soft materials and type D used for hard materials, allowing the measurement of the initial indentation and/or the indentation after a specified time" (no full stop on the card). The text of ISO 868:2003, which the Polish standard introduces, we read in full — the sample extract covers all clauses 1–9.

ACCORDING TO THE TEXT OF ISO 868:2003. The standard was prepared by ISO/TC 61 "Plastics", subcommittee SC 2 "Mechanical properties"; the third edition replaced the second (ISO 868:1985). Scope (1): indentation hardness of plastics and ebonite with a durometer of type A (softer materials) or type D (harder), with a reading of the initial indentation, after a specified time, or both; the names "Shore type A durometer" and "type D". The method is empirical and is intended mainly for control purposes; there is no simple relationship between the result and any fundamental property of the material; for specification purposes for softer materials the standard recommends ISO 48 "Rubber, vulcanized or thermoplastic — Determination of hardness (hardness between 10 IRHD and 100 IRHD)". Reference (2): ISO 291:1997 (standard atmospheres for conditioning and testing of plastics). Principle (3): a specified indenter is forced into the material under specified conditions and the depth of penetration is measured; the hardness is inversely related to the penetration and depends on the modulus of elasticity and the viscoelastic properties of the material; the shape of the indenter, the force and its duration affect the result, so results from durometers of different types and from other hardness testers may have no simple relationship. Apparatus (4): presser foot with a hole 3 mm ± 0.5 mm in diameter, at least 6 mm from any edge of the foot; indenter of hardened steel rod 1.25 mm ± 0.15 mm in diameter, shaped according to Figure 1 (type A) or 2 (type D); indicator from 0 at the full extension of the indenter of 2.50 mm ± 0.04 mm to 100 at zero extension (foot and indenter pressed against a flat glass plate), possibly with a maximum indicator for the instantaneous reading; calibrated spring, force F = 550 + 75·HA (mN) for type A and F = 445·HD (mN) for type D. Specimens (5): thickness at least 4 mm — it may be built up of thinner layers, but the result may differ from that of a single specimen because the layers are not in complete contact; measurement at least 9 mm from the edge (unless it is known that closer gives the same result); surface flat enough for the foot to be in contact over a radius of at least 6 mm from the indenter; on rounded, uneven or rough surfaces a satisfactory measurement cannot be made. Calibration (6): durometer vertical, indenter on a metal spacer (a pin about 2.5 mm high and about 1.25 mm in diameter) on the pan of a balance; the measured force is to agree with the formula to within ± 75 mN (type A) or ± 445 mN (type D); the balance or calibration device is to measure the force to an accuracy of 3.9 mN (A) or 19.6 mN (D). Conditioning (7): for materials whose hardness does not depend on humidity, durometer and specimens at least 1 h at the test temperature, for the others — according to ISO 291 or the material specification; a durometer moved from a cold place to a warmer one is kept in a desiccator or a sealed container until its temperature exceeds the dew point; test in one of the standard atmospheres of ISO 291, unless the material specification states otherwise. Procedure (8): specimen on a hard, horizontal, flat surface; durometer vertical, indenter at least 9 mm from the edge; apply the presser foot as quickly as possible, without shock, parallel to the surface, with pressure only sufficient for full contact (better reproducibility is obtained with a stand or a mass — recommended 1 kg for type A and 5 kg for type D); reading after 15 s ± 1 s, and the instantaneous reading — within 1 s or as the maximum of the indicator; five measurements at different positions, at least 6 mm apart, and the mean; above 90 type A units type D is recommended, below 20 type D units — type A. Report (9): among others the type of durometer, the thickness of the specimen and the number of layers, the temperature (and humidity, when relevant), individual values with the time of reading and the mean; notation e.g. "Shore hardness A/15:45" (type A, reading after 15 s, result 45) or "D/1:60" (type D, reading within 1 s or maximum, result 60).

STATUS (as of 08.10.2026). The PKN card of PN-EN ISO 868:2005 (Polish version) has no withdrawal label: title "Plastics and ebonite -- Determination of indentation hardness by means of a durometer (Shore hardness)" (our translation), publication 28-10-2005, 11 pages, price group F, Chemistry Sector, KT 141 Plastics, "Introduces: EN ISO 868:2003 [IDT], ISO 868:2003 [IDT]", "Replaces: PN-EN ISO 868:2004 - English version", ICS 83.080.01. PKN search, term "ISO 868" (08.10.2026): 25 items, three with the number 868 — only this one is current; withdrawn are PN-EN ISO 868:2004 (English version) and PN-ISO 868:1998 (Polish version). evs.ee catalogue: ISO 868:2003 in force since 14.04.2003, in the history ISO 868:1985.

HOW MANY LABORATORIES AND IN WHAT FORM (copy of the accreditation scope database and current PCA documents, read on 08.10.2026). In the database copy the number appears in 10 records at 9 laboratories; in the current PCA documents (issues from 28.07.2023 to 27.07.2026) it occurs 11 times at the same laboratories; no entry is suspended. Notation: "PN-EN ISO 868:2005" — AB 005, AB 033, AB 067, AB 147, AB 163 (separately method A and method D), AB 169 (two entries), AB 771; without a year — AB 023 and AB 128 (with the addition "met. A i D" (methods A and D)). Alongside this standard in the same cell there are: PN-80/C-04238 or PN-C-04238:1980 (AB 005, AB 033, AB 169), PN-ISO 48:1998 (AB 033), ISO 48-4 and DIN 53505 (AB 128), standards for insulators PN-EN 62217:2013-06 and PN-EN 61462:2009 (AB 067), and at AB 169 in the entry on ageing — PN-ISO 188:2000 and PN-ISO 37:2007+AC1:2008. The "Laboratories" tab (term "PN-EN ISO 868") shows 7 laboratories (8 records); it does not show AB 005 and AB 033, whose notation in the database begins with the number of the Polish standard for rubber (PN-80/C-04238, PN-C-04238:1980). The term does not pick up standards with other numbers.

WHAT THE LABORATORIES TEST (PCA documents). Quantity: Shore hardness, scales A and D (AB 023, AB 033, AB 128, AB 147, AB 163) or only A (AB 005, AB 067, AB 169); AB 771 does not give the scale. Subject: plastics and products made of them (AB 023, AB 128, AB 147, AB 163); plastics and rubber (AB 005); sole and upper materials for footwear — solid and microcellular rubbers, plasticized PVC compounds, thermoplastic rubbers, polyurethanes, EVA copolymers — with separate ranges for rubber and for plastics and ebonite (AB 033); rubber and rubber products (AB 128); rubber vulcanizate and conveyor belts, also after accelerated heat ageing (AB 169); rubber components of friction braking devices (AB 771); composite, polymer and organic-material insulators above 1 kV (AB 067). Ranges: 0–98 Sh A (AB 005), 0–100 Sh A and 0–100 Sh D (AB 033), 30–90 Sh A and 20–90 Sh D (AB 147), up to 99 Sh D (AB 163), up to 100 Sh A (AB 067), 10–90 °Sh (AB 169).

WHERE A SEEMINGLY CORRECT RESULT IS EASY TO GET. First — the subject scope: the standard applies to plastics and ebonite, and for softer materials it recommends ISO 48 (rubber, IRHD hardness) for specification purposes; five laboratories also apply it to rubber (AB 005, AB 033, AB 128, AB 169, AB 771), usually alongside standards for rubber (PN-C-04238, ISO 48, ISO 48-4) — the report should state according to which document the measurement was made. Second — reading time: the reading after 15 s and the instantaneous reading (within 1 s or maximum) are different results, which is why the standard requires the time to be recorded in the form "A/15:45" or "D/1:60"; the number "Shore A 45" alone does not say when it was read. Third — the scale: type A and type D cannot be converted into each other; above 90 A units type D is recommended (the range of AB 005 reaches 98 Sh A). Fourth — the specimen: thickness at least 4 mm, measurement at least 9 mm from the edge, flat surface over a radius of 6 mm; a specimen built up of layers may give a different result, and on rounded or rough surfaces a satisfactory measurement is impossible — this matters when testing finished products such as brake components or insulators. Fifth — an empirical result: Shore hardness has no simple relationship with the modulus of elasticity or with the results of other hardness testers (clauses 1.2 and 3).

WHAT WE DO NOT GIVE. WE DO NOT GIVE the dimensions of the tips of the type A and D indenters from Figures 1 and 2 (angles and radii). We did not have the Polish text of PN-EN ISO 868:2005 — the description is based on the text of ISO 868:2003, which this standard introduces.

Method principle

The indenter of a durometer — type A for softer materials or type D for harder ones — is pressed into the specimen by the force of a spring (F = 550 + 75·HA mN for type A, F = 445·HD mN for type D) and the hardness is read in units from 0 (full extension of the indenter, 2.50 mm) to 100 (zero extension); the hardness is inversely related to the depth of penetration and depends on the modulus of elasticity and the viscoelasticity of the material. Reading after 15 s ± 1 s or instantaneous (within 1 s or maximum); the result is the mean of five measurements (ISO 868:2003, clauses 3, 4 and 8). The method is empirical and is intended mainly for control purposes.

Applications

• Plastics and ebonite — Shore A and D hardness; in the current accreditation scopes 9 laboratories
• Control of plastic products: pipes and fittings, plastic products, composite and polymer insulators (AB 067, AB 147, AB 163)
• Sole materials for footwear, vulcanizates, conveyor belts and rubber brake components — at laboratories that also apply the standard to rubber, usually alongside standards for rubber
• Change of hardness after accelerated heat ageing (AB 169, together with PN-ISO 188:2000)

Key parameters

Standard

Standard number

PN-EN ISO 868:2005 (wersja polska; wprowadza EN ISO 868:2003 [IDT] i ISO 868:2003 [IDT])

Title (PL)

Tworzywa sztuczne i ebonit — Oznaczanie twardości metodą wciskania z zastosowaniem twardościomierza (twardość metodą Shore’a)

Title (EN)

Plastics and ebonite — Determination of indentation hardness by means of a durometer (Shore hardness)

Step-by-step procedure

1. Specimen

   Thickness at least 4 mm (built-up layers may give a different result), dimensions allowing measurement at least 9 mm from the edge, flat surface over a radius of 6 mm from the indenter (ISO 868:2003, 5).

2. Conditioning

   Durometer and specimens at least 1 h at the test temperature; humidity-sensitive materials — according to ISO 291 or the specification; test in a standard atmosphere of ISO 291 (7).

3. Measurement

   Specimen on a hard, horizontal plane; durometer vertical; apply the presser foot quickly, without shock, parallel, with pressure only sufficient for full contact; reading after 15 s ± 1 s or instantaneous (8.1).

4. Repetitions

   Five measurements at different positions, at least 6 mm apart; result — the mean; above 90 A units change to type D, below 20 D units — to type A (8.2).

5. Report

   Type of durometer, thickness of the specimen and number of layers, temperature (and humidity), individual values with the reading time and the mean — notation e.g. "A/15:45" (9).

6. Calibration of the spring

   Periodically on a balance with a spacer; force in agreement with the formula to within ± 75 mN (A) or ± 445 mN (D) (6).

Required equipment and apparatus

Health and safety (OHS)

• The standard does not formulate specific safety requirements; operation of the durometer and stand — according to the manufacturer instructions
• TECHNICAL NOTE: the standard applies to plastics and ebonite — for softer materials it recommends ISO 48 for specification purposes; A and D readings, and readings after 15 s and instantaneous ones, are not interchangeable

Frequently asked questions