How vitrified and porcelain tiles are made in Morbi
Vitrified and porcelain tiles are pressed from fine spray-dried clay and feldspar powder and fired in long roller kilns until the body is almost glass-like. Under ISO 13006 and EN 14411 they belong to group BIa: dry-pressed tiles with water absorption of 0.5% or less. The Indian trade uses several names for what sits in that group:
- GVT and PGVT. A glazed body decorated by inkjet printers, then left matt or polished. Most marble- and wood-look tiles are made this way.
- Double charge. Two layers of coloured powder pressed together, then polished. The design runs a few millimetres deep.
- Full body. Colour through the whole thickness, so chips show less.
- Large slabs. Formats such as 800 × 1600 mm and 1200 × 2400 mm, often 6 to 15 mm thick, made for floors, walls, kitchen tops and furniture.
After firing, tiles are polished or left as fired, cut square on rectifying machines, then sorted on a line into grade, shade (tonality) and calibre (size band). Each box is labelled with these codes. The inspection is a check on that sorting line. Morbi, in Gujarat, is the Town of Export Excellence for ceramic tiles and sanitaryware.
What we check on vitrified tiles and slabs
| Check | How it is checked | What fails |
|---|---|---|
| Shade lot | Tiles from several cartons of one shade code laid out as a panel, viewed from standing height and compared with the approved sample and other lots | Visible shade or gloss steps inside one lot; carton shade code not matching the tiles |
| Calibre and size | Length and width measured on each sampled tile; calibre code compared with measured size | Two calibres in one carton or pallet; out of the declared tolerance |
| Rectified edges and squareness | Edges checked with a straight edge and square; tiles butted together | Wedging, bowed sides, open joints in a dry lay |
| Flatness and warpage | Centre and edge curvature measured with a gauge or straight edge and feelers; tiles laid on a flat table | Corner lift or centre crown that will cause lippage on the floor |
| Surface quality | Face viewed from about 1 m in even light, the way ISO 10545-2 describes | Print-head lines, colour spots, pinholes, glaze drops, polishing marks, edge and corner chips |
| Polished surface staining | Marker or ink test on a spare tile, wiped after a set time, as the buyer's protocol sets | Mark that will not clean off: open micropores not sealed after polishing |
| Design faces | Number of different print faces counted against the specification | Too few faces, so the same vein repeats across a floor |
| Water absorption and strength | Factory lab boil test and breaking-strength test witnessed, or tiles sealed for an outside lab | Absorption above 0.5%, so the tile is not BIa; breaking strength below the declared value |
| Carton and box marking | Labels checked for grade, shade, calibre, size, quantity, producer and origin | Missing codes, wrong producer, wrong count per box |
Slip resistance cannot be measured reliably on site. A claimed R rating or wet DCOF value must come from a lab report on the same tile and surface finish.
Common vitrified and porcelain tile defects and how they are classed
| Defect | Typical cause | Class |
|---|---|---|
| Cracked slab in a crate, with loose sharp pieces | Crate not braced, slab flexed in handling | Critical (handling safety) |
| Mixed shade or calibre in one carton or pallet | Sorting line error or end-of-lot top-up | Major |
| Warpage beyond tolerance | Uneven kiln temperature across the roller bed | Major |
| Hairline crack through the body | Pressing or drying fault | Major |
| Permanent stain on a polished tile | Polished surface not sealed | Major |
| Print-head line across the design | Blocked inkjet nozzle | Major or minor by visibility |
| Small edge chip, glaze spot | Handling, kiln debris | Minor |
Your defect list decides the final class.
Large porcelain slabs: extra checks
Slabs bring their own risks because they are thin for their size and are often cut by fabricators after delivery. The inspector adds:
- Bow along the length. Measured with a long straight edge; a bowed slab cannot be laid flat or bonded to a cabinet top.
- Thickness at several points. Thin areas crack when a fabricator cuts sink holes.
- Mesh or fibre backing. Bond checked at the edges where the slab has a reinforcing back.
- Bookmatch and sequence. Slabs sold as bookmatched pairs or vein-match sets checked for numbering and that the pattern continues across the joint.
- Crating. Slabs face-to-face with protective film or foam, braced in A-frames or wooden crates that are ISPM 15 marked, with lifting points clear.
Market rules and the US duty order
- EU and UK. Ceramic tiles are construction products. In the EU they carry CE marking with a declaration of performance under the harmonised standard EN 14411. Great Britain still accepts CE for construction products; see UKCA and CE marking. The inspector checks that the marking and declaration name the same factory and tile group.
- US standard. ANSI A137.1 sets tile properties in the US; it calls for a wet DCOF of 0.42 or more for tiles used on level interior floors expected to be walked on when wet. A wet DCOF claim needs a lab report.
- US countervailing duty. The US Department of Commerce issued a countervailing duty order on ceramic tile from India on 16 June 2025 (case C-533-929). The scope covers floor, wall, porcelain, mosaic and other tile under 3.2 cm thick, including slabs over 1 m². Cash deposit rates at the order were 3.45% for Antiqa Minerals, 3.06% for Win-Tel Ceramics and 3.18% for all others. The parallel anti-dumping investigation ended with a negative final determination (Federal Register, 23 April 2025). Rates can change on review; ask your customs broker for the current deposit. Because the rate follows the producer, the inspector records the producing factory and checks carton marks against it.
- Gulf. Tiles fall under Saudi building-material rules; see SASO and SABER.
Packing, loading and your purchase order
Tiles fail in transit at the corners. Cartons should be tight, with corner protectors and edge boards on the pallet and strapping that does not cut into the top row. Pallets should not overhang. A tile container usually reaches its weight limit before its volume limit, so the load plan spreads weight over the floor and keeps pallets from shifting.
Write these into your purchase order:
- Format, thickness, finish (matt, satin, polished, structured) and rectified or not.
- Grade (export or first quality), one shade and one calibre per pallet, and the maximum number of shade lots per order.
- Size, squareness and warpage tolerances, or the standard they follow.
- Number of design faces, and stain-resistance and slip values with test reports.
- Carton marking (shade, calibre, producer, origin), pallet build and slab crate design.
For the BIII wall tiles and BIb–BIIb floor tiles, see ceramic wall tiles.
Sources
- DGFT: Appendix 1B, Towns of Export Excellence (Morbi)
- Federal Register: Ceramic tile from India, countervailing duty order (16 June 2025)
- Federal Register: Ceramic tile from India, final negative determination of sales at less than fair value (23 April 2025)
- ISO 13006:2018, Ceramic tiles: definitions, classification, characteristics and marking
- GOV.UK: Construction products regulation in Great Britain