The phrase "a range of hardness" is correct and usable in written English.
It can be used when discussing the varying levels of hardness in materials, substances, or objects.
Example: "The testing revealed a range of hardness in the different samples of rock collected from the site."
Alternatives: "a spectrum of hardness" or "a variety of hardness levels".
Artists' pencils come in a range of hardness, depending on how much clay is used to bind the graphite.
The biotic ligand model provides a quantitative framework for assessing metal toxicity over a range of hardness, pH and dissolved organic carbon (DOC) levels.
The samples collected from different localities show a range of hardness.
Artist pencils come in a range of hardness and softness.
Urethane, obtainable in a range of values of hardness, possesses some inherent advantages, and provides additional versatility to steel tools.
Concerning the desired physical properties including transparency, low melt viscosity and melting temperature as well as a wide range of hardness grades from soft (flexible) to hard (rigid), three different hardness grades of thermoplastic polyurethanes were found to be the best candidates for this lens application.
Nano-indentation tests were conducted using a Berkovich indenter on five materials spanning a wide range of hardness and plasticity.
Various sizes of indenters and loads allow a wide range of hardness to be measured.
The thermal drill has the advantage of simplicity of design and operations and the ability to penetrate ice over a range of densities and hardness while maintaining sample integrity.
Compression testing of tri-isotropic (TRISO) carbon/silicon carbide-coated fuel particles between anvil materials with a wide range of hardnesses was investigated.
Glasses are essentially super cooled liquids and they possess a unique combination of properties: transparency with or without colour, durability, electrical and thermal resistance, a range of thermal expansions, with hardness, rigidity and stability density, refractive index (Copley 2001).
