Glaze hardness is how well the glazed face of a tile resists scratching and wear. Wall tile glazes are usually softer than floor tile glazes, because walls do not face foot traffic and a glossy, decorative glaze matters more there.
A softer glaze is not a defect on a wall. It becomes a problem when wall tiles are used on floors, on worktops or in areas with heavy cleaning and knocks.
Two ways hardness is described
You will see two kinds of figure in catalogues and test reports. They measure different things.
- Scratch hardness on the Mohs scale, from 1 (talc) to 10 (diamond), which says which reference minerals can scratch the glaze.
- Surface abrasion resistance to ISO 10545-7, which wears the glaze with a rotating abrasive load and gives the PEI class from 0 to 5.
Mohs values are a simple scratch comparison and are often declared by factories rather than tested in an accredited laboratory. The PEI class comes from a standard test and is more useful when you compare products. Both are explained in more detail in the Mohs hardness of vitrified tiles and PEI rating for tiles.
Why it matters on a wall
Even on walls, glazes face some wear. These are the situations where hardness shows:
- Kitchen backsplashes are wiped often, sometimes with abrasive pads, which dulls a soft gloss glaze.
- Shower walls are cleaned with brushes and descaling products.
- Commercial washrooms, hospitals and schools get harder cleaning and more knocks.
- Metallic and glitter effect glazes are often softer than the base glaze and can scratch or wear first.
Matt glazes often hide fine scratches better than high gloss, though they may hold dirt more. Ask for a sample of each finish and try a kitchen scourer on a corner before you choose. Chemical and stain resistance, tested to ISO 10545-13 and ISO 10545-14, also matter for cleaning and should be on the same report.
Why it matters for claims
Most hardness complaints come from tiles used in the wrong place. A gloss wall tile laid on a bathroom floor will show wear paths and scratches quickly. Your product labels and catalogue should state clearly when a tile is for walls only. The reasons are set out in whether wall tiles can be used on floors.
What to ask the factory
- The PEI class or a statement that the tile is for wall use only.
- The declared Mohs value, and whether it was tested by a laboratory.
- Chemical and stain resistance results to ISO 10545-13 and ISO 10545-14.
- Whether effect glazes on decor tiles have been tested separately from the base tile.
Next step
We check the reports for each glaze in your range and flag tiles that should be labelled wall only. To review your range, book a free sourcing review.