All technical data drawn directly from Sibelco and Primo Pro datasheets and product pages. All temperatures are in °C as stated in the datasheets — this is the most reliable reference. Rows marked with dashes (—) indicate information not yet available.
| Use Case | Recommended Clays | Firing Range (°C) | Fired Shrinkage | Water Absorption |
|---|---|---|---|---|
| Wheel Throwing (smooth, plastic clay) | Standard Stoneware RW1002, FSZ, White Stoneware (Atelier W), WFSZ 2002, Cacao RW1302, Toast RW1802, PRIMO PW20, WMS 2002GG, WMSB, Hanjiki Half Porcelain, PRIMO Highfire Porcelain | 1000–1300°C (varies by clay) | 5.0–19% (porcelain higher) | 0.1–4.5% when fired correctly — check individual clay spec |
| Hand Building (moderate grog) | Toast RW1802, WM2502, W2502, W2505, WMS 2002GG, WMS 2005B, WMS 2502, WMSB, Cacao RW1302, R-Terracotta, Nigra 2002, PRIMO PW20 | 1000–1280°C | 4.9–7.0% | 1.5–3.9% |
| Large Sculpting (high grog essential) | RTM5015 Sculptural Stoneware, PRGF4005 High Fire Gris | 1000–1300°C | RTM5015: 3.5% PRGF: 4.6% |
RTM5015: 6.0% — glaze for functional use PRGF: 7.4% — not for unglazed functional use |
| Throwing & Modelling (high-fire grogged) | PRGI-4002 Toasted Brown High Fire | 1240–1300°C | 7.1% @1300°C | 3.7% @1300°C |
| Fine Modelling / Porcelain (experienced potters) | PRIMO PW20, Hanjiki Half Porcelain, PRIMO Highfire Porcelain, PRIMO Lowfire Porcelain (pending) | 1160–1300°C | PW20: ~16% Highfire: ~19% Hanjiki: pending |
PW20: 2% @1200°C Highfire: 0.1% @1260°C Hanjiki: pending |
| Speckle Effects (fire above 1150°C for spots) | WMS 2002GG (rose-grey), WMS 2005GG (rose-grey, coarser), WMSB (apricot-khaki), WMS 2005B (apricot-buff), WMS 2502 (cream) | 1000–1280°C | 4.9–6.8% | 1.5–3.5% |
| Warm Earthy Tones | Cacao RW1302 (chocolate brown), Toast RW1802 (terracotta-red), WMSB (apricot-khaki), R-Terracotta (light red), Atelier R (red — max 1160°C) | 1000–1240°C | Cacao: ~5.2% Toast: 6.0–7.4% Atelier R: 6.5% |
Cacao: 0% @1220°C Toast: 0.4% @1240°C Atelier R: 4.5% @1100°C — glaze for functional use |
| Dark / Statement Work | Nigra 2002 Black Stoneware, Cacao RW1302 (chocolate brown) | 1000–1240°C | Nigra: 7.0% Cacao: ~5.2% |
Nigra: 2.5% @1200°C Cacao: 0% @1220°C |
| Functional Ware (Low Water Absorption) | WFSZ 2002, Cacao RW1302, Toast RW1802, PRIMO PW20, PRIMO Highfire Porcelain, Standard Stoneware RW1002, Nigra 2002 | 1000–1300°C (fire at upper end of range) | 5.0–19% | WFSZ 2002: 0.1% @1200°C Cacao: 0% @1220°C Toast: 0.4% @1240°C PW20: 2% @1200°C Highfire: 0.1% @1260°C Standard: 1.8% @1240°C Nigra: 2.5% @1200°C |
| Schools & Community Studios (reliable, forgiving) | Standard Stoneware RW1002, White Stoneware (Atelier W), FSZ, Toast RW1802, PRIMO PW20 | 1000–1260°C | 5.0–16% | Consistent firing results across a wide temperature range. Good glaze compatibility. |
Recommended ClaysStandard Stoneware RW1002, FSZ, White Stoneware (Atelier W), WFSZ 2002, Cacao RW1302, Toast RW1802, PRIMO PW20, WMS 2002GG, WMSB, Hanjiki Half Porcelain, PRIMO Highfire Porcelain
Firing Range1000–1300°C (varies by clay)
Fired Shrinkage5.0–19% (porcelain higher)
Water Absorption0.1–4.5% when fired correctly — check individual clay spec
Recommended ClaysToast RW1802, WM2502, W2502, W2505, WMS 2002GG, WMS 2005B, WMS 2502, WMSB, Cacao RW1302, R-Terracotta, Nigra 2002, PRIMO PW20
Firing Range1000–1280°C
Fired Shrinkage4.9–7.0%
Water Absorption1.5–3.9%
Recommended ClaysRTM5015 Sculptural Stoneware, PRGF4005 High Fire Gris
Firing Range1000–1300°C
Fired ShrinkageRTM5015: 3.5%
PRGF: 4.6%
Water AbsorptionRTM5015: 6.0% — glaze for functional use
PRGF: 7.4% — not for unglazed functional use
Recommended ClaysPRGI-4002 Toasted Brown High Fire
Firing Range1240–1300°C
Fired Shrinkage7.1% @1300°C
Water Absorption3.7% @1300°C
Recommended ClaysPRIMO PW20, Hanjiki Half Porcelain, PRIMO Highfire Porcelain, PRIMO Lowfire Porcelain (pending)
Firing Range1160–1300°C
Fired ShrinkagePW20: ~16%
Highfire: ~19%
Hanjiki: pending
Water AbsorptionPW20: 2% @1200°C
Highfire: 0.1% @1260°C
Hanjiki: pending
Recommended ClaysWMS 2002GG (rose-grey), WMS 2005GG (rose-grey, coarser), WMSB (apricot-khaki), WMS 2005B (apricot-buff), WMS 2502 (cream)
Firing Range1000–1280°C
Fired Shrinkage4.9–6.8%
Water Absorption1.5–3.5%
Recommended ClaysCacao RW1302 (chocolate brown), Toast RW1802 (terracotta-red), WMSB (apricot-khaki), R-Terracotta (light red), Atelier R (red — max 1160°C)
Firing Range1000–1240°C
Fired ShrinkageCacao: ~5.2%
Toast: 6.0–7.4%
Atelier R: 6.5%
Water AbsorptionCacao: 0% @1220°C
Toast: 0.4% @1240°C
Atelier R: 4.5% @1100°C — glaze for functional use
Recommended ClaysNigra 2002 Black Stoneware, Cacao RW1302 (chocolate brown)
Firing Range1000–1240°C
Fired ShrinkageNigra: 7.0%
Cacao: ~5.2%
Water AbsorptionNigra: 2.5% @1200°C
Cacao: 0% @1220°C
Recommended ClaysWFSZ 2002, Cacao RW1302, Toast RW1802, PRIMO PW20, PRIMO Highfire Porcelain, Standard Stoneware RW1002, Nigra 2002
Firing Range1000–1300°C (fire at upper end of range)
Fired Shrinkage5.0–19%
Water AbsorptionWFSZ 2002: 0.1% @1200°C
Cacao: 0% @1220°C
Toast: 0.4% @1240°C
PW20: 2% @1200°C
Highfire: 0.1% @1260°C
Standard: 1.8% @1240°C
Nigra: 2.5% @1200°C
Recommended ClaysStandard Stoneware RW1002, White Stoneware (Atelier W), FSZ, Toast RW1802, PRIMO PW20
Firing Range1000–1260°C
Fired Shrinkage5.0–16%
Water AbsorptionConsistent firing results across a wide temperature range. Good glaze compatibility.
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