Sovereignty Module: Set the Shelf
Complete Kiln Furniture Making: From Clay to Shelf
Kiln furniture supports and separates pots during firing. This campaign covers shelf making, post construction, stilts, wadding, and kiln loading strategies.
Chapter 1: Kiln Furniture Types
| Item | Purpose | Material | Reusability |
|---|---|---|---|
| Kiln shelf | Flat surface to hold pots | High-alumina clay or cordierite | 50-200+ firings |
| Posts (pillars) | Support shelves at different heights | High-alumina clay | 100+ firings |
| Stilts | Elevate glazed pots (prevent sticking) | High-alumina clay with wire points | 1-5 firings |
| Wadding | Separate pot from shelf (wood firing) | Alumina + kaolin + sand | Single use |
| Kiln wash | Protective coating on shelves | Alumina + kaolin slurry | Reapply as needed |
| Setters (tile) | Support tiles on edge | High-alumina clay | 50+ firings |
| Saggar | Enclose pots for atmosphere control | Stoneware clay + grog | 10-20 firings |
Chapter 2: Kiln Shelf Making
Kiln shelf recipe: 1) 50% calcined alumina (or ground firebrick). 2) 30% ball clay. 3) 20% grog (coarse, 20-40 mesh). 4) Mix dry ingredients thoroughly. 5) Add water to form stiff clay. 6) Roll slab to 3/4-1 inch thick. 7) Cut to desired shape (round or rectangular). 8) Dry slowly (2-3 weeks) to prevent warping. 9) Fire to cone 10 (2345°F) before first use. 10) Apply kiln wash to top surface.
| Shelf Size | Kiln Type | Thickness | Weight | Capacity |
|---|---|---|---|---|
| 10 inch round | Small electric | 5/8 inch | 5 lbs | 3-5 small pots |
| 12x12 inch square | Medium electric | 3/4 inch | 8 lbs | 4-6 medium pots |
| 14x14 inch square | Large electric | 3/4 inch | 12 lbs | 6-8 medium pots |
| 12x24 inch rectangle | Gas kiln | 1 inch | 15 lbs | 8-12 pots |
| 15x15 inch square | Wood kiln | 1 inch | 18 lbs | 6-10 pots |
Chapter 3: Posts and Supports
Post making: 1) Roll clay coil (1-2 inch diameter). 2) Cut to desired height (1, 2, 3, 4, 6 inches). 3) Flatten both ends (must sit level). 4) Dry and fire to cone 10. 5) Use three posts per shelf (three points define a plane, never wobbles). 6) Stack posts directly above each other (load transfers straight down).
| Post Height | Use | Pot Size |
|---|---|---|
| 1 inch | Plates, shallow bowls | Under 2 inches tall |
| 2 inches | Bowls, small pots | 2-4 inches tall |
| 3 inches | Mugs, medium pots | 4-6 inches tall |
| 4 inches | Vases, tall pots | 6-8 inches tall |
| 6 inches | Large vases, tall pieces | 8-12 inches tall |
Chapter 4: Kiln Wash and Wadding
Kiln wash recipe: 1) 50% calcined alumina (EPK or similar). 2) 50% kaolin (EPK or similar). 3) Mix with water to thin cream consistency. 4) Brush 3-4 coats on shelf top surface. 5) Allow each coat to dry before applying next. 6) Kiln wash prevents glaze drips from bonding to shelf. 7) Reapply when wash becomes thin or damaged.
Wadding recipe (for wood firing): 1) 50% alumina hydrate. 2) 25% kaolin. 3) 25% fine sand. 4) Mix with water to stiff putty. 5) Roll into small balls (1/2 inch diameter). 6) Place 3 balls under each pot. 7) Wadding prevents pot from sticking to shelf in wood firing. 8) Remove wadding marks from pot bottom after firing.
Chapter 5: Kiln Loading Strategy
| Principle | Rule | Reason |
|---|---|---|
| Three posts per shelf | Always use exactly three | Three points never wobble |
| Posts aligned vertically | Stack directly above lower posts | Load transfers straight down |
| No touching | Pots must not touch each other or walls | Glaze fuses pots together |
| Clearance | 1/4-1/2 inch between pots | Allows heat circulation |
| Heavy on bottom | Largest, heaviest pots on lowest shelf | Stability, even heat |
| Tight loading | Fill shelves efficiently | Maximizes kiln capacity |
| Glaze-free foot | Wipe glaze from bottom 1/4 inch | Prevents sticking to shelf |
Loading process: 1) Apply fresh kiln wash to shelves if needed. 2) Place bottom shelf on kiln floor (or on posts above floor). 3) Load pots on shelf (no touching, 1/4 inch clearance). 4) Place three posts on shelf (aligned with posts below). 5) Place next shelf on posts. 6) Repeat until kiln is full. 7) Leave 1-2 inches clearance at top. 8) Close kiln door or lid. 9) Begin firing schedule.
Reference Card
- Three posts per shelf, always (three points define a plane and never wobble; four posts will rock if the shelf is not perfectly flat; always use exactly three posts per shelf). 2. Align posts vertically (each post must be directly above the post below it; offset posts create bending stress on the shelf that can cause cracking or collapse). 3. Kiln wash saves shelves (a coat of kiln wash on the shelf surface prevents glaze drips from bonding permanently; without kiln wash, a single glaze drip can ruin an expensive shelf). 4. Never let pots touch (glazed pots that touch during firing will fuse together permanently; always maintain at least 1/4 inch clearance between all pots and between pots and kiln walls). 5. Wipe the foot clean (glaze on the bottom of a pot will fuse it to the kiln shelf; always wipe glaze from the bottom 1/4 inch of every pot before loading). 6. Heavy pots go on the bottom (loading heavy pots on lower shelves provides stability and ensures even heat distribution; top-heavy loading risks shelf collapse). 7. Homemade kiln furniture saves money (commercial kiln shelves are expensive; shelves and posts made from high-alumina clay and grog perform well and cost a fraction of commercial furniture). 8. Good loading maximizes every firing (efficient loading means more pots per firing, which means less fuel, less time, and more production; plan your loading before you start).