ASTM C1895 Standard Test Method for Determining Mohs Scratch Hardness

The standard "ASTM C1895 Standard Test Method for Determining Mohs Scratch Hardness," published by the American Society for Testing and Materials (ASTM), describes a test method for determining the Mohs scratch hardness of ceramic tile, glass tile, and other hard surfaces. Mohs scratch hardness is a useful tool for determining the scratch resistance of ceramic tiles. Scratch resistance is determined by visually observing the surface of the ceramic tile after attempting to scratch it with a tool of known hardness.

The equipment used in these tests includes:

Hardness meters.
Hardness tester sled: A fixture used to hold the hardness tester at an angle of 70 degrees plus or minus 5 degrees. The sled should be capable of applying a force of 3,2 kg plus or minus 0,2 kg to the point where the hardness point contacts the test specimen. This can be achieved by adding an auxiliary weight to the sled. The sled should be equipped with a handle to assist in pulling the hardness tester across the test specimen. The total weight required to apply the required force varies depending on the total weight in the sled and, if an auxiliary weight is used, its location on the sled.
Jeweler's loupe or other suitable magnifying device.
Sharpening stone or whetstone: A surface made of material suitable for sharpening sharpening tools. Diamond-coated sharpening stones and sharpening stones made of aluminum oxide or corundum are known to work well.
Optional staining solution, such as 1 percent methylene blue solution.

The test sample must consist of at least one tile. Test samples up to 15 cm x 15 cm should be left uncut for testing. Samples with sides greater than 15 cm may be reduced to no less than 15 cm for ease of use.

Hardness tips can wear with use. Before testing, examine the tip of the tip under a magnifying glass to ensure a sharp tip with even taper. Hardness tips may need to be sharpened to remove flat spots or imperfections. To sharpen a hardness tip, remove the hardness tip and place it in the chuck of an electric drill. Hold the hardness tip at an angle of approximately 20 degrees to the grinding stone, and use the electric drill to rotate the hardness tip. Excessive heat from friction can alter the hardness of the tip. To prevent overheating, keep the sharpening stone wet and do not attempt to sharpen for more than 10 seconds.

In short, ASTM C1895 is a standard test method designed to evaluate the Mohs scratch hardness of ceramic tile, glass tile, and other hard surfaces. This method determines which standard mineral (based on the Mohs scale) can visibly scratch the surface of a sample under specified conditions. This standard provides a simple and reproducible way to measure a material's scratch resistance and compares it to Mohs hardness standards (ranging from softer minerals such as talc to the hardest corundum).

This method is widely used in quality control, material selection and research, especially in the construction, ceramics, aerospace, electronics and coating industries.

In general, this testing method consists of the following steps:

Surface preparation: The material is cleaned and prepared according to standard instructions.
Scratch tests: Using a set of reference minerals of known Mohs hardness, each is scratched across the surface with a controlled force.
Visual inspection: Observers check to see which minerals are visibly visible on the surface.
Hardness rating: The Mohs hardness value is determined by the hardest mineral that produces a noticeable scratch.

The test relies on visual detection of surface traces, so operator consistency and appropriate lighting are critical. Because it does not address all safety concerns, users should wear appropriate personal protective equipment and adhere to laboratory protocols.

Friedrich Mohs was a German mineralogist best known for developing the Mohs scale for measuring mineral hardness. This scale ranks minerals based on their ability to scratch each other. It is a simple yet effective method for determining and comparing the hardness of natural materials.

The Mohs scale was one of the first practical and systematic ways to classify minerals and made hardness testing both accessible and easily reproducible in the field. While more precise hardness tests are available today, the Mohs scale remains a fundamental concept in mineralogy and materials engineering.

The hardness level of each mineral on the classic Mohs scale, where each mineral can be scratched off, is as follows:

1 = Talc: Baby powder
2 = Gypsum: Chalk, drywall
3 = Calcite: Limestone, tums
4 = Fluorite: Fluorite crystals
5 = Apatite: Tooth enamel
6 = Orthoclase: Feldspar in granite
7 = Quartz: Sand, glass
8 = Topaz: Some precious stones
9 = Corundum: Sapphires, rubies
10 = Diamond: The hardest known natural material

Mohs scratch hardness is important because it provides a quick and practical way to assess a material's scratch resistance. This directly impacts its durability, function, and appearance, especially in real-world use. This method is considered important for the following reasons:

Durability and abrasion resistance: Materials with a higher Mohs hardness can better resist surface damage. They are useful in flooring, countertops, tiles, veneers, lenses, and electronics, where daily contact, abrasion, or friction can cause scratches. For example, ceramic tiles with a hardness of 7+ are not easily scratched by sand (quartz). Phone screens need a hardness above 6 to resist scratches from coins or keys.
Material selection and design: Helps designers choose materials suitable for environments subject to high traffic and wear (e.g., hospitals, public transportation, kitchens). For example, when choosing glass for solar panels or windows, it must be resistant to scratches from windblown dust (usually quartz-based).
Quality control and compliance with standards: ASTM C1895 and similar standards use Mohs hardness to ensure products meet scratch resistance specifications. A ceramic tile advertised as scratch resistant must pass a hardness level test to validate its claim.
Field mineral identification: In geology and mining, this is a quick, low-tech method for identifying unknown minerals. Geologists can scratch a mineral with a known object (such as a knife or fingernail) to estimate its hardness.

As a result, ASTM C1895 is a widely used testing approach for evaluating scratch resistance using the Mohs scale. Its simplicity, affordability, and applicability to ceramic and hard surfaces make it a valuable tool in quality control and specifications across industries.

Our organization, which has been supporting businesses across all sectors for years through a wide range of testing, measurement, analysis, and evaluation activities, has a strong team of employees who closely follow global developments in science and technology and are constantly improving themselves. In this context, we also provide testing services in accordance with the ASTM C1895 Standard Test Method for Determining Mohs Scratch Hardness.