A Guide to the Barcol Hardness Test Method & Standard

When the integrity of your materials is on the line, having a reliable testing method is non-negotiable.

A significant operational issue can often be traced back to a material that didn't meet its hardness specification. That's why we want to provide a clear explanation of the Barcol hardness test, a key procedure in modern quality control.

Fundamentals of the Barcol Hardness Test

The barcol hardness test method is a direct approach for measuring the hardness of materials by assessing their resistance to indentation (Wassell et al., 1992; Ling et al., 2024; Bharadwaja et al., 2021).

It uses a well-made, spring-loaded instrument with a sharp, flat-ended steel cone. When pressed firmly against a surface, the hardness value is read directly from the instrument, with higher numbers indicating harder materials (Bala et al., 2005; Ling et al., 2024; Bharadwaja et al., 2021). 

Modern instruments, such as a Digital Barcol Hardness Tester – QualiHBA, display this value on a clear screen.

Because of this straightforward and effective process, the instrument is widely used in research and industry to compare composite formulations or monitor the effects of additives (Bala et al., 2005; Ling et al., 2024; Bharadwaja et al., 2021). 

Here are a few key examples:

- Aerospace Composites: Picture a technician on the production line for a composite airplane wing. If the resin hasn't cured properly, the structural integrity of the part is compromised. They use the Barcol tester to get a hard number that confirms whether the part is ready for the next stage of assembly, preventing a faulty component from moving down the line.

- Marine Manufacturing: For fiberglass boat hulls, the test confirms the hull has hardened correctly, preventing potential issues like delamination or structural weakness out on the water.

- General Quality Control: It's also the go-to method for spot-checking the hardness of other rigid plastics and softer metals like aluminum alloys.

The Barcol Test Compared to Other Methods

You are likely familiar with other hardness testing methods, so it's useful to see how the barcol hardness test method fits in.

For checking rigid plastics and aluminum alloys directly on the production floor, we’re confident in saying the Barcol tester is the superior choice for its specific application. Its portability and focus on a certain range of materials give it a distinct advantage.

Here's how it stacks up against other common methods:

- Rockwell: This test is the heavyweight champion for very hard metals like steel. It's not suitable for the softer metals and composites the Barcol is designed for.

- Shore D: While also a portable test, the Shore durometer is intended for hard rubbers and semi-rigid plastics. For truly rigid composites, the Barcol impressor provides a more accurate and meaningful measure.

- Brinell: The Brinell test is great for castings and forgings but not practical for the thinner materials or plastics where the Barcol method proves its value.

Barcol Hardness Test Standard

To ensure that readings are consistent and meaningful across the industry, the entire process is governed by an official barcol hardness test standard for each material type. Following these standards isn't about formality; it’s about producing reliable data you can stand behind. The two main standards are:

ASTM D2583: For Rigid Plastics

This is the specific standard for testing the indentation hardness of both reinforced and non-reinforced rigid plastics.

If you are working with composites, fiberglass, or any other hard thermoset plastics, this is the document that outlines the correct procedure and conditions (Wassell et al., 1992; Ling et al., 2024; Bharadwaja et al., 2021).

ASTM B648: For Aluminum Alloys

This standard covers the barcol hardness test procedure for determining the hardness of aluminum alloys. It provides the necessary guidelines for getting accurate readings on softer metals and ensuring they meet their required specifications.

The Barcol Hardness Test Procedure: A Step-by-Step Guide

This barcol hardness test procedure is straightforward when you approach it with discipline. Following these steps will ensure your data is both accurate and repeatable.

Step 1: Prepare the Material Surface

Before you do anything else, inspect the surface you intend to test. It must be clean, dry, and free of any oils or debris. A smooth, flat area is necessary for the instrument's base to sit flush against the material.

This is critical, as the test is quite sensitive to surface conditions (Wassell et al., 1992; Bala et al., 2005; Fowler et al., 1994).

Step 2: Calibrate the Instrument

This is a non-negotiable step. Before beginning, check the instrument's accuracy using the standard test discs.

If the reading is outside the acceptable range, all measurements that follow will be incorrect. A quick calibration check is the foundation of trustworthy data.

Step 3: Position the Tester and Apply Pressure

Place the instrument flat on the prepared surface, making sure the indenter point is perpendicular to the material (Wassell et al., 1992; Bala et al., 2005; Fowler et al., 1994).

Apply pressure in a single, smooth, and continuous motion. Inconsistent application of pressure is the most common reason for getting erratic readings.

Step 4: Take and Record the Readings

For a single representative value, you need to take multiple readings. Move the instrument to different spots, always staying at least 3mm (or 1/8 inch) away from any edge or previous indentation.

With a digital instrument like the QualiHBA, the precise value is displayed instantly, making it easy to record and average your readings for a final, reliable hardness number.

Qualitest: Your Partner in Hardness Testing

At Qualitest, we have a deep focus on this technology. We believe that effective testing equipment should be accessible without a major capital investment.

Our Digital Barcol Hardness Tester – QualiHBA is a product we stand behind because it is built to simplify the barcol hardness test procedure and perform reliably. It's the kind of straightforward, dependable tool that quality managers can count on to do its job effectively.

We invite you to review the specifications for the QualiHBA on our product page. We are confident it will meet the demands of your quality control program.

References:

1. Wassell, R., Mccabe, J., & Walls, A. (1992). Subsurface deformation associated with hardness measurements of composites.. Dental materials : official publication of the Academy of Dental Materials, 8 4, 218-23. https://doi.org/10.1016/0109-5641(92)90088-t

2. Bala, O., Uçtaşli, M., & Tüz, M. (2005). Barcoll hardness of different resin-based composites cured by halogen or light emitting diode (LED).. Operative dentistry, 30 1, 69-74.

3. Ling, L., Lai, T., & Malyala, R. (2024). Mechanical Properties and Degree of Conversion of a Novel 3D-Printing Model Resin. Polymers, 16. https://doi.org/10.3390/polym16243562

4. Fowler, C., Swartz, M., & Moore, B. (1994). Efficacy testing of visible-light-curing units.. Operative dentistry, 19 2, 47-52.

5. Bharadwaja, K., Rao, S., & Rao, T. (2021). Investigation of hardness & tribology behavior of Epoxy and Sio2 composite: An experimental study. Materials Today: Proceedings. https://doi.org/10.1016/j.matpr.2020.12.653