Barcol | EUROLAB

What Is Barcol?

Barcol hardness is read directly from a scale, based on the penetration depth produced when a spring-loaded indenter is pressed into the material. The instrument is hand-held and gives an instant result. Its common use is on glass-fibre-reinforced polyester and similar composites.

Purpose of Barcol

The purpose is to quickly verify that resin has cured sufficiently, particularly in field-produced composite structures. Insufficient cure directly reduces mechanical strength and chemical resistance; Barcol is the most practical indicator of this.

Which Products Is Barcol Applied To?

Glass-fibre-reinforced polyester (GRP) products
Composite tanks, pipes and boat hulls
Gelcoat-covered surfaces
Rigid plastic sheets
Field-produced composite structural elements

In Which Sectors Is Barcol Used?

CompositesMaritimeConstructionChemistryEnergy

Standards Related to Barcol

ASTM D2583 (indentation hardness of rigid plastics by means of a Barcol impressor)
EN 59 (glass-reinforced plastics — Barcol hardness)
ISO 868 (Shore hardness — complementary for softer materials)

Barcol Conditions

Instrument: Barcol impressor with a spring-loaded indenter
Surface: Flat, clean and supported; the measurement point is reported as the mould-side or machined surface
Number of measurements: Repeated the number of times defined in the standard, due to high scatter
Temperature: Measurement temperature is recorded; resin hardness is temperature-sensitive

Equipment for Barcol

Barcol hardness tester (impressor)
Calibration disc set
Surface cleaning equipment
Thermometer

Sample Requirements for Barcol

The measurement point must not land on a fibre bundle; a location representative of the resin must be chosen.
The part must be supported so it does not flex during measurement.
Wax, mould release and dirt on the surface must be cleaned off.
Thickness must be sufficient that the indenter's effect does not reach the back surface.

Duration of Barcol

The measurement gives an instant result; it takes seconds. This speed is the method's main advantage for field use.

Barcol Procedure

1The instrument is verified with calibration discs.
2The measurement surface is cleaned.
3The instrument is pressed perpendicular to the surface with a steady force.
4The value is read from the scale.
5The measurement is repeated at different points.
6Outliers are excluded per the standard and the average is calculated.

Barcol Acceptance Criteria

The method standard defines how the test is performed, not what the result should be. The acceptance limit comes from the material standard, the product specification or the customer's technical drawing; this page therefore gives no numerical limit.

Evaluation of Results

The result is given together with the average and spread. In cure assessment, the measurement is compared against the fully cured value declared by the resin manufacturer for that material; this value is defined by the material manufacturer, not the laboratory.

Barcol Report

Specimen identification, material type and cast/batch number, if any
Specimen geometry, dimensions and preparation method
Standard and test conditions applied
Test temperature and ambient conditions
Measured values and calculated quantities
Fracture surface or indentation photographs (where applicable)
Measurement uncertainty (if requested)
A statement that the result applies only to the specimen submitted for testing

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 authorisations

Related Regulations

EN 10204 (inspection documents for metallic products)
EU 305/2011 Construction Products Regulation (for products used in construction)
Harmonised standards applied according to the product family

Mekanik Testler — What Does This Testing Field Cover?

The section below describes the field that the Barcol 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 Barcol

Does the Barcol value give a numerical degree of cure?

No. It provides a practical indicator of adequate cure. Thermal analysis methods such as DSC are used for a precise degree of cure.

Why do measurements vary?

The fibre/resin distribution on the surface varies from point to point. The standard therefore requires statistical assessment of multiple measurements rather than a single one.