Ceramic Tiles and Porcelain From China: Water Absorption, PEI Wear Rating and the Batch Colour Problem
Tile sourcing looks easy until you reorder. The first order arrives, the customer is happy, you reorder six months later from the same factory and the "same" ivory is two shades warmer. Now every wall it touches looks wrong. That single problem — batch-to-batch colour drift — is the reason tile is a discipline category, not a commodity one.
Water Absorption Class Comes First
Water absorption drives everything else: where the tile can be used, how strong it is, how frost-resistant it is. The standard classification runs from BIa (under 0.5 percent, fully vitrified porcelain) through BIb (0.5 to 3 percent), BIIa, BIIb, and BIII (above 10 percent, the porous wall-tile end).
Floor tile in wet or outdoor areas should be BIa porcelain. A high-absorption tile on a bathroom floor will take on water, stain, and in a freezing climate spall apart as the water expands. Ask for the absorption figure and the test method, and if the supplier only says "porcelain" without a number, treat it as a guess.
PEI Wear Rating and Where It Belongs
The PEI rating (from PEI I to PEI V) describes abrasion resistance for floor use. PEI III is fine for residential floors, PEI IV for commercial traffic, PEI V for heavy public use. Some cheaper glossy tiles used on floors are only PEI II, which will show wear paths within a couple of years in a hallway. Confirm the rating and make sure it matches the placement — suppliers sometimes quote one rating and ship another.
Slip Resistance — the Value Nobody Asks For
Slip resistance is measured as an R value (R9 to R13, higher is grippier) or as a DCOF number. Indoor dry floors can be R9; bathrooms and kitchens want R10 or better; outdoors, pool surrounds and commercial wet areas want R11 to R13. This is a safety and liability issue, not a cosmetic one, and it does not correlate with price — some very expensive polished tiles are dangerously slick when wet.
The Batch Colour Issue and How to Control It
Colour comes from the glaze formulation and the firing curve. Kiln temperature and dwell time vary run to run, and different production days produce different shades. The professional way to manage this is to ask the factory to reserve a single batch (often identified by a batch or lot code) for your whole order and to hold stock so future reorders can match. For large projects, get all the tile fired in one run.
When you receive the goods, keep the batch code from the cartons on file. If you ever need to top up, you can ask for that exact batch. Without it you are reordering blind. Also ask for physical colour samples approved from production, not a digital mock-up or a glossy catalogue image, and approve against natural daylight and against the client's own reference if there is one.
Format, Calibration and Grout Width
Tile nominal size is rarely the true size, and tiles from different moulds within a batch can differ. Ask for the calibration or "rectified" status — rectified tile is cut to exact size and lets you use a narrow grout line, which changes the whole look. Non-rectified tile needs a wider joint to absorb size variation. Specify your intended grout width and confirm the tile tolerance supports it.
Packing, Weight and Logistics
Tile is heavy — often 15 to 25 kg per square metre of product, plus pallet and crating — so freight is a real cost component and breakage in transit is common. Ask about packing method (foam, corner protection, pallet type) and claims history. If breakage rates on a comparable shipment were high, spec stronger crating even at extra cost; a five percent breakage rate wipes out a thin margin.
What to Get in Writing
- Water absorption class with the measured percentage
- PEI wear rating and intended application
- Slip resistance R value or DCOF
- Rectified or non-rectified, with dimensional tolerance
- Batch/lot code held for the order, and confirmation of reserved stock for reorders
- Physical approved samples signed off from production, plus reference photos in daylight
- Packing method, breakage allowance and inspection standard
Tile is one of the few categories where a single well-managed reorder request — "reserve the batch, send me the lot code, hold stock" — is worth more than any discount. Colour consistency is the product.