# Sovereignty Module: Fire the Glaze

## Complete Pottery Glazing and Kiln Firing: From Raw Ash to Glossy Surface

Glazing transforms porous earthenware into waterproof, food-safe, beautiful vessels. This campaign covers glaze chemistry, ash glazes, kiln construction, firing schedules, and troubleshooting.

### Chapter 1: Glaze Fundamentals

| Component | Function | Sources | Percentage |
|---|---|---|---|
| Silica (glass former) | Creates the glassy surface | Quartz, sand, flint | 55-75% |
| Alumina (stiffener) | Prevents glaze from running off | Clay, feldspar | 5-15% |
| Flux (melter) | Lowers melting temperature | Wood ash, limestone, feldspar, borax | 15-35% |
| Colorants | Add color | Metal oxides (iron, copper, cobalt) | 1-10% |
| Opacifiers | Make glaze opaque | Tin oxide, zirconium | 5-15% |

| Firing Temperature | Name | Cone | Glaze Type | Clay Body |
|---|---|---|---|---|
| 1,650-1,940°F | Low fire (earthenware) | 06-1 | Lead, boron, alkaline | Red/white earthenware |
| 2,100-2,300°F | Mid fire (stoneware) | 4-7 | Feldspathic, ash | Stoneware |
| 2,300-2,400°F | High fire (stoneware/porcelain) | 8-12 | Feldspathic, ash | Stoneware, porcelain |

### Chapter 2: Ash Glazes (From Scratch)

| Ash Source | Character | Color | Flux Strength | Availability |
|---|---|---|---|---|
| Hardwood (oak, maple) | Smooth, reliable | Tan to green | Moderate | Abundant |
| Softwood (pine, cedar) | Rough, variable | Brown to amber | Low | Abundant |
| Straw/grass | Smooth, high silica | Clear to pale | High | Agricultural |
| Fruit wood (apple, cherry) | Smooth | Green to amber | Moderate | Orchards |
| Bone ash | Smooth, opaque | White, creamy | High | Butchering byproduct |
| Seaweed | Variable | Green, blue-green | High | Coastal |

Simple ash glaze recipe: 1) Collect wood ash (hardwood preferred). 2) Sieve ash through fine screen (remove charcoal chunks). 3) Wash ash: soak in water, stir, let settle, pour off water (removes soluble alkalis). 4) Repeat washing 2-3 times. 5) Dry washed ash. 6) Basic recipe: 40% washed wood ash + 40% feldspar + 20% ball clay. 7) Mix with water to cream consistency. 8) Sieve through 80-mesh screen. 9) Apply to bisque-fired pottery (dip, pour, or brush). 10) Fire to cone 8-10 (2,300-2,380°F). 11) Result varies with ash source (the beauty of ash glazes is their natural variation).

### Chapter 3: Kiln Construction

| Kiln Type | Max Temp | Fuel | Difficulty | Cost | Capacity |
|---|---|---|---|---|---|
| Pit firing | 1,300-1,650°F | Wood, dung | Very low | Free | Small-medium |
| Sawdust kiln | 1,200-1,500°F | Sawdust | Very low | Very low | Small |
| Updraft kiln (brick) | 2,000-2,400°F | Wood | Moderate | Low-moderate | Medium |
| Downdraft kiln | 2,000-2,400°F | Wood, gas | High | Moderate | Medium-large |
| Anagama (tunnel) | 2,300-2,400°F | Wood (massive quantity) | Very high | Moderate | Large |
| Electric kiln | 2,300°F | Electricity | Low (purchase) | High | Small-medium |
| Raku kiln | 1,800-2,000°F | Gas, wood | Low-moderate | Low | Small |

Simple updraft kiln construction: 1) Dig foundation trench (firebox below, chamber above). 2) Build firebox: brick-lined channel, 12-18 inches wide, 12 inches tall. 3) Build floor: grate or perforated shelf above firebox (allows heat to rise). 4) Build chamber walls: firebrick or dense clay brick, 24-36 inches diameter. 5) Walls: 4-6 inches thick (insulation). 6) Door: removable bricks on one side (loading/unloading). 7) Top: partially covered (damper controls draft). 8) Chimney: not required for updraft (heat rises through top). 9) Fire in firebox, heat rises through floor into chamber. 10) This kiln can reach cone 6-10 (2,200-2,380°F) with sustained wood firing.

### Chapter 4: Firing Process

| Stage | Temperature Range | Rate | Time | What Happens |
|---|---|---|---|---|
| Water smoking | Room temp - 400°F | Slow (100°F/hr) | 2-4 hours | Remaining moisture driven off |
| Burnout | 400-1,100°F | Moderate (200°F/hr) | 3-4 hours | Organic matter burns out |
| Quartz inversion | 1,063°F | Very slow (50°F/hr) | Pass slowly | Quartz crystal structure changes (cracking risk) |
| Sintering | 1,100-1,650°F | Moderate (200°F/hr) | 2-3 hours | Clay particles begin fusing |
| Vitrification | 1,650-2,400°F | Moderate (150-200°F/hr) | 3-6 hours | Glass formation, glaze melts |
| Soaking | Target temp | Hold | 15-30 min | Even heat distribution, glaze smooths |
| Cooling | Target to room temp | Slow (natural) | 12-24 hours | DO NOT OPEN KILN (thermal shock) |

Bisque firing: 1) Load bone-dry greenware into kiln (pieces must be completely dry). 2) Leave space between pieces (air circulation). 3) Fire slowly to 1,800-1,940°F (cone 06-04). 4) Rate: 100°F per hour to 400°F, then 200°F per hour to target. 5) Hold at target for 15-30 minutes. 6) Cool slowly (do not open kiln until below 200°F). 7) Result: hard but porous (ready for glazing). 8) Bisque ware absorbs glaze like a sponge (the porosity is the point).

### Chapter 5: Troubleshooting

| Problem | Cause | Fix |
|---|---|---|
| Crawling (glaze pulls away) | Dusty bisque, glaze too thick, oil contamination | Clean bisque, thin glaze, handle with clean hands |
| Crazing (fine cracks in glaze) | Glaze contracts more than clay (tension) | Add silica to glaze, or use different clay |
| Shivering (glaze flakes off) | Glaze contracts less than clay (compression) | Reduce silica in glaze |
| Pinholing (tiny holes) | Gases escaping through glaze | Fire slower, soak longer at peak temp |
| Running (glaze flows off pot) | Too much flux, fired too hot | Reduce flux, lower temperature, apply thinner |
| Dunting (cracks during cooling) | Cooled too fast (thermal shock) | Cool kiln more slowly, don't open early |
| Bloating (bubbles in clay) | Over-fired, impurities in clay | Lower temperature, use cleaner clay |

### Reference Card

1. Bone dry before firing (any moisture in clay = steam explosion in kiln; dry completely before loading). 2. Slow through quartz inversion (1,063°F is dangerous; heat and cool slowly through this point or pots crack). 3. Never open a hot kiln (thermal shock cracks everything; wait until below 200°F to open). 4. Ash makes glaze (wood ash is a complete glaze flux; mixed with clay and feldspar, it creates beautiful surfaces). 5. Test tiles save pots (test every new glaze on small tiles before applying to finished work). 6. Glaze thickness matters (too thin = dry and rough; too thick = runs off pot onto kiln shelf). 7. Wax the foot (apply wax resist to bottom of pots before glazing; glaze on the bottom fuses pot to shelf). 8. Fire transforms earth (raw clay becomes stone through fire; glazing adds beauty and function to that transformation).