Complete Clay Shrinkage Database 2025
The definitive professional database of clay shrinkage rates for pottery and ceramics. Comprehensive data for all clay types including firing temperatures, shrinkage percentages, absorption rates, and professional recommendations for accurate pottery calculations.
Clay Shrinkage Quick Reference
| Clay Type | Drying Shrinkage | Firing Shrinkage | Total Shrinkage | Firing Temp | Absorption |
|---|---|---|---|---|---|
| Porcelain | 6-8% | 8-12% | 14-20% | 1260-1300°C | 0-3% |
| Stoneware | 5-7% | 6-8% | 11-15% | 1200-1280°C | 1-6% |
| Earthenware | 4-6% | 4-6% | 8-12% | 950-1100°C | 10-20% |
| Fire Clay | 3-5% | 5-7% | 8-12% | 1100-1300°C | 5-15% |
| Ball Clay | 7-10% | 8-12% | 15-22% | 1200-1300°C | 0-2% |
Detailed Clay Shrinkage Profiles
Porcelain Clay
Shrinkage Characteristics:
Physical Properties:
Common Brands & Types:
- • Grolleg: 16-18% total shrinkage
- • New Zealand Halloysite: 15-17%
- • Tile #6: 14-16%
- • English Porcelain: 17-19%
- • German Porcelain: 15-17%
Professional Tips for Porcelain:
- • Allow extra drying time to prevent cracking from rapid moisture loss
- • Plan for 15-20% linear shrinkage minimum when designing pieces
- • Use slower firing curves to accommodate high shrinkage rates
- • Consider clay body composition - higher kaolin content = higher shrinkage
Stoneware Clay
Shrinkage Characteristics:
Working Properties:
Popular Stoneware Bodies:
- • Standard 112: 11-13% total
- • Laguna B-Mix: 12-14% total
- • Coleman Porcelain: 13-15% total
- • Highwater Phoenix: 11-13% total
- • Sheffield Pottery #900: 12-14% total
Stoneware Advantages:
Stoneware offers the best balance of workability and predictable shrinkage rates. It's ideal for both functional pottery and sculptural work, with moderate shrinkage that's easier to predict and account for in design calculations.
Earthenware Clay
Shrinkage Characteristics:
Unique Properties:
Common Earthenware Types:
- • Red Earthenware: 8-10% total
- • White Earthenware: 9-11% total
- • Buff Earthenware: 8-12% total
- • Terra Cotta: 6-9% total
- • Majolica Body: 10-12% total
Earthenware Considerations:
While earthenware has the lowest shrinkage rates, its high porosity requires glazing for functional use. The predictable, low shrinkage makes it excellent for large sculptural work and decorative pieces where dimensional accuracy is important.
How to Calculate Clay Shrinkage
Linear Shrinkage Formula
Example Calculation:
Reverse Calculation:
Volume Shrinkage
Important Note:
Volume shrinkage is approximately 3× the linear shrinkage rate because shrinkage occurs in all three dimensions (length × width × height).
Volume Calculation:
Planning Implications:
High-shrinkage clays like porcelain lose significant volume, affecting wall thickness and interior spaces in hollow forms.
Factors Affecting Clay Shrinkage
Clay Body Composition
High Plasticity Clays
Ball clay, bentonite - Higher shrinkage (15-25%)
Moderate Plasticity
Fire clay, stoneware clay - Medium shrinkage (8-15%)
Non-Plastic Materials
Silica sand, grog, feldspar - Reduce shrinkage
Environmental Factors
Drying Conditions
Fast drying increases cracking risk, doesn't change total shrinkage
Firing Temperature
Higher temperatures = more shrinkage and vitrification
Firing Atmosphere
Reduction firing can affect final shrinkage by 1-2%
Clay Shrinkage FAQ
How do I test my clay's shrinkage rate?
Make test tiles with precise measurements (100mm works well). Mark, dry, bisque fire, and glaze fire, measuring at each stage. This gives you exact shrinkage data for your specific clay and firing conditions.
Why does my clay shrink more than expected?
High plastic clay content, overly wet working consistency, higher firing temperatures, or longer firing holds can all increase shrinkage beyond typical ranges.
Can I reduce clay shrinkage?
Add non-plastic materials like grog (fired clay particles) or sand to reduce shrinkage. 10-20% grog can reduce total shrinkage by 2-4%. However, this may affect workability and strength.
How accurate are published shrinkage rates?
Published rates are guidelines. Actual shrinkage varies with working consistency, drying conditions, firing schedule, and kiln atmosphere. Always test with your specific conditions for accurate results.
Calculate Your Clay Shrinkage
Use our professional shrinkage calculator for accurate pottery planning