Full Clay Specification Guide
All data sourced directly from Sibelco and Primo Pro technical datasheets and product pages. Throughout this guide, "plastic" in the context of clay means workable and easy to shape.
| Clay | Firing Range (°C) | Fired Colour | Grog | Shrinkage (fired) | Water Absorption | Best For | Notes |
|---|---|---|---|---|---|---|---|
| Standard Stoneware RW1002 (V2) | 1000–1240°C | White – cream | 10%, 0–0.2mm | 5.2% @1150°C 6.0% @1200°C 7.0% @1240°C | 4.5% @1150°C 3.0% @1200°C 1.8% @1240°C | Wheel throwing, hand building | Low grog, high plasticity (easy to work and shape). Reliable all-rounder for beginners and experienced potters alike. |
| FSZ – Fine Mid-Fire Cream | 1000–1200°C | Cream – grey | Not stated (high plasticity body) | 5.0% @1140°C 6.0% @1200°C | 3.8% @1140°C 1.0% @1200°C | Wheel throwing, hand building | High plasticity stoneware. Smooth and responsive on the wheel. Good for functional ware. |
| White Stoneware (Atelier W) | 1000–1260°C | Cream | Not stated | 6.0% @1200°C | 2.3% @1200°C | Wheel throwing, hand building | Consistent cream-firing studio clay suited to a wide range of work. |
| White Stoneware with Grog W2502 | 1000–1280°C | Cream | 25%, 0–0.2mm | 5.1% @1200°C | 3.9% @1200°C | Wheel throwing, hand building | Wide firing range. Added grog improves stability for larger forms. |
| White Stoneware with Grog W2505 | 1000–1280°C | Cream | 25%, 0–0.5mm | 5.1% @1200°C | 3.9% @1200°C | Hand building, larger forms | Same grog % as W2502 but coarser particle size (0–0.5mm vs 0–0.2mm). Better suited to larger hand-built pieces. |
| WFSZ 2002 – Silky Caramel | 1000–1200°C | Light cream – light grey | 20%, 0–0.2mm | 7.5% @1200°C | 0.1% @1200°C | Wheel throwing, hand building | Vitreous body with only 0.1% water absorption at 1200°C. Dense, strong fired result well suited to functional ware. |
| WM2502 – Cream Stoneware with Grog | 1000–1300°C | White – cream – grey | 25%, 0–0.2mm | 5.2% @1200°C | 3.5% @1200°C | Wheel throwing, hand building | Widest firing range in the collection. Higher chamotte adds stability for larger forms. |
| WMS 2002GG – Stoneware with Speckle | 1000–1250°C | Rose – grey with spots (spots from 1150°C) | 20% black chamotte, 0–0.2mm | 6.0% @1200°C | 2.0% @1200°C | Wheel throwing, hand building | Fire below 1150°C for a plain surface. Popular for contemporary decorative and functional work. |
| WMS 2005GG – Stoneware with Speckle | 1000–1250°C | Rose – grey with spots (spots from 1150°C) | 20% black chamotte, 0–0.5mm | 5.3% @1200°C | 2.7% @1200°C | Wheel throwing, hand building | Similar to WMS 2002GG but coarser chamotte (0–0.5mm). Spots appear from 1150°C. |
| WMS 2502 – Stoneware with Speckle (Cream) | 1000–1280°C | Cream with spots (spots from 1150°C) | 25%, 0–0.2mm | 4.9% @1200°C | 3.5% @1200°C | Wheel throwing, hand building | Cream base with speckle. Wider firing range than the 2002 speckle series. Spots appear from 1150°C. |
| WMSB – Warm Mid-Fire Spotted Buff | 1000–1250°C | Apricot – yellow – khaki with spots (from 1150°C) | Not stated | 6.8% @1200°C | 1.5% @1200°C | Wheel throwing, hand building | Warm spotted finish appearing from 1150°C. Distinctive earthy aesthetic. |
| WMS 2005B – Stoneware with Speckle (Buff) | 1000–1250°C | Apricot – yellow – khaki with spots (from 1150°C) | 20%, 0–0.5mm | 5.5% @1200°C | 2.8% @1200°C | Wheel throwing, hand building | Warm buff spotted clay with coarser chamotte than WMSB. Spots appear from 1150°C. |
| Toast RW1802 | 1000–1240°C | Terracotta – red brown | 18%, 0–0.2mm | 6.0% @1150°C 6.8% @1200°C 7.4% @1240°C | 3.5% @1150°C 1.0% @1200°C 0.4% @1240°C | Wheel throwing, hand building | Warm earthy tones. Excellent for functional ware at the upper end of its range (0.4% absorption at 1240°C). |
| Cacao Stoneware RW1302 | 1000–1220°C Optimal: 1220°C (Cone 6) | Walnut – deep chocolate brown | 13%, 0–0.2mm | ~5.2% @1150°C ~5.5% @1200°C ~5.6% @1220°C | ~4.5% @1150°C ~0.5% @1200°C ~0% @1220°C | Wheel throwing, hand building, small sculpture | Fully vitreous at 1220°C / Cone 6 (0% water absorption). Works beautifully with iron, copper and reactive glazes. Unglazed: natural earthy satin finish. |
| R-Terracotta | 1000–1200°C | Light red – red brown | Not stated | 6.3% @1100°C | 3.5% @1100°C | Wheel throwing, hand building | Datasheet describes as a midfire body despite the Terracotta name. Classic warm red colour. Glaze thoroughly for any food-contact use. |
| Red Stoneware (Atelier R) | 1000–1160°C | Red | Not stated | 6.5% @1100°C | 4.5% @1100°C | Wheel throwing, hand building | Maximum firing temperature is 1160°C — lower than most other clays in this range. Check kiln compatibility carefully. Higher water absorption — glaze thoroughly for functional ware. |
| Red Stoneware with Grog R2505 | 1000–1200°C | Red | 25%, 0–0.5mm | 5.0% @1100°C | 5.0% @1100°C | Hand building, sculpting | Red body with substantial grog for larger built or sculptural work. Higher water absorption — glaze for any functional use. |
| Nigra 2002 – Black Stoneware | 1000–1240°C | Black | 20% black chamotte, 0–0.2mm | 7.0% @1200°C | 2.5% @1200°C | Wheel throwing, hand building | Striking black fired colour. Check glaze compatibility carefully — some glazes react unpredictably on dark bodies. |
| RTM5015 – Sculptural Stoneware | 1000–1280°C | Rose – yellow – green | 50%, 0–1.5mm | 3.5% @1200°C | 6.0% @1200°C | Large-scale sculpture only | Engineered for large sculptural builds. 50% chamotte gives low shrinkage (3.5%). Not suited to throwing. Glaze for functional use — 6% water absorption. |
| PRGI-4002 – Toasted Brown High Fire | 1240–1300°C | Light toasted brown | 40% impalpable (up to 80 Mesh) | 7.1% @1300°C (drying: 6.9%) | 3.7% @1300°C | Wheel throwing, modelling | High-fire body suited to both throwing and modelling smooth pieces with fine detail. Requires kiln capable of minimum 1240°C. |
| PRGF4005 – High Fire Grogged Gris | 1240–1300°C | Light tan brown (raw colour: grey) | 40%, 0–0.5mm | 4.6% @1300°C (drying: 6.2%) | 7.4% @1300°C | Sculpture, murals, Raku | Designed for sculpture, murals and Raku. Not suited to throwing. High water absorption (7.4%) — not suited to unglazed functional ware. Requires minimum 1240°C. |
| Hanjiki Half Porcelain 10kg | 1160–1300°C* | White-firing (semi-porcelain) | None | Wheel throwing, modelling | Semi-porcelain body. Pulls well for handles, responds extremely well with glazes — lustre and high gloss finish. Strong, with excellent resistance to warping when used and fired correctly. | ||
| PRIMO Highfire Porcelain 10kg | 1160–1300°C | White, very translucent | None (porcelain body) | ~19% | 0.1% @1260°C | Wheel throwing, modelling | Smooth, white-firing porcelain body — responsive on the wheel and particularly suited to small and medium pieces. Very translucent. Best suited to experienced potters — requires care in forming and drying. |
| PRIMO Production White PW20 | 1160–1260°C | Fires very white (some faint speckling possible) | None | ~16% wet to fired @1200°C | 4% @1160°C 2% @1200°C | Wheel throwing, hand building | Best-selling throwing body for tableware makers. Smooth, plastic and easy to trim — great for beginners and professionals. Also a good hand-building clay. Works especially well with Abbots Clear glaze (1160–1200°C). |
Still not sure which clay is right for you? Get in touch with our team — we're always happy to help.