For porcelain slabs sold as kitchen worktops, order tests for water absorption, breaking strength, stain resistance, chemical resistance, thermal shock and flatness. Add any food-contact testing your market requires.
Most of these tests come from the ISO 10545 series, which was written for tiles. They still give useful, comparable results for worktops. Ask for reports from an accredited laboratory, on the exact product and thickness you buy.
The core tests
- Water absorption, ISO 10545-3: confirms the porcelain body, with absorption of 0.5% or less, which keeps liquids out.
- Breaking strength and modulus of rupture, ISO 10545-4: shows how much load the slab carries before it breaks, which matters for overhangs and spans.
- Stain resistance, ISO 10545-14: tests how easily common staining agents are removed.
- Chemical resistance, ISO 10545-13: tests the surface against household chemicals, acids and alkalis.
- Thermal shock resistance, ISO 10545-9: tests whether the slab survives rapid temperature changes.
- Dimensions, thickness and flatness, ISO 10545-2: checks size, squareness and bow.
Useful extra tests
- Surface abrasion for glazed slabs, ISO 10545-7, or deep abrasion for unglazed slabs, ISO 10545-6, to show wear resistance.
- Linear thermal expansion, ISO 10545-8, useful near hobs and for outdoor kitchens.
- Impact resistance, ISO 10545-5, which gives a measure of resistance to dropped objects.
- Lead and cadmium release from glazed surfaces, ISO 10545-15, useful supporting evidence for food-contact questions.
Food contact
Tile tests do not by themselves show that a worktop meets food-contact rules. In the US, the food-equipment material standard NSF/ANSI 51 is widely used, and some slab products are certified to it for specific sizes and thicknesses. In the EU, food-contact materials fall under Regulation (EC) No 1935/2004.
Rules and their application to worktops differ by market. Our guide on whether slabs are food-safe explains what to ask for.
Results to watch most closely
For worktops, three results deserve the most attention. Breaking strength must suit the thickness and the overhangs your customers plan. Stain resistance should be checked on the exact finish, because polished and matt surfaces of the same design can behave differently. Thermal shock matters because worktops meet hot pans and cold water in quick succession.
Making the reports useful
Our guide on reading a lab certificate explains how to check a report, and the wider list of tile tests covers floor and wall uses.
- Check that each report names the factory, the product, the thickness and the finish you are buying.
- Check that the lab is accredited for the test, and that the report is recent.
- For a large order, have a sample from your own production lot tested, not only the factory's type test.
- Compare results against the standard's limits and any figures you agreed in your specification.
Next step
We select tests for your market and use, draw samples from your production lot and have them tested at an accredited lab. To plan testing for worktop slabs, book a free sourcing review.