Pottery and Ceramics

Why This Matters

Before pottery, you cannot boil water safely, store grain without it spoiling, carry liquids over distance, or cook anything more complex than roasted meat on a stick. A single fired clay pot unlocks dozens of downstream technologies: brewing, cheese-making, soap production, metal smelting (crucibles), water storage, and eventually glassmaking. Pottery is one of the oldest human technologies for a reason — it is among the most transformative.

The Core Principle

Clay is a naturally occurring mineral (decomposed feldspar rock) that becomes plastic when wet, holds any shape when dried, and becomes permanently hard and waterproof when heated above 600°C. The process is irreversible — fired clay cannot become soft again. This is what makes pottery permanent and useful.

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What You Need

For finding and processing clay:

• A water source (stream, river, pond)
• Digging tool
• Buckets, baskets, or any containers
• Flat drying surface (boards, flat rocks, bark)
• Fabric or fine-woven basket for straining (optional but helpful)

For hand-building:

• Clay (processed and wedged — see below)
• Flat work surface (smooth stone, wood plank)
• Scraping tool (shell, smooth stone, wood spatula)
• Smoothing tools (wet finger, smooth pebble, piece of leather)
• Cutting tool (sharp shell, stone flake, string)
• Rolling tool (smooth, straight stick)

For firing:

• Large quantity of dry firewood (hardwood preferred)
• Dry kindling and tinder
• Flat, dry ground at least 3 meters from any structure
• Broken pottery pieces (grog) or sand for kiln floor
• For pit firing: digging tools
• For kiln: adobe bricks or stones, clay mortar

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Step 1: Finding Clay

Clay is everywhere — it is one of the most abundant materials on Earth. Look in these locations:

• River banks and stream beds: Where slow-moving water deposits fine particles. Look for smooth, sticky deposits along the inside of bends.
• Road cuts and eroded hillsides: Exposed clay layers are often visible as smooth, distinct bands of color (grey, red, tan, white).
• Under topsoil: Dig down 30-60 cm in most areas. Below the organic topsoil layer, you often find clay subsoil.
• Dry lake beds and pond margins: Cracked, smooth surfaces that are slippery when wet.

The Pinch Test

Pick up a sample. Wet it, and roll it between your fingers. Good clay feels smooth, sticky, and plastic — it holds whatever shape you press it into without cracking. Bad material feels gritty (too much sand), crumbles (too little clay), or is slimy but will not hold shape (silt, not clay).

Roll a pencil-thin coil about 15 cm long. Wrap it around your finger. If it bends smoothly without cracking, it has enough plasticity for pottery. If it cracks and breaks apart, it needs more clay-rich material mixed in.

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Step 2: Processing Clay

Raw clay from the ground usually contains rocks, roots, organic matter, and inconsistent particle sizes. Processing removes impurities and creates a uniform, workable material.

Method A: Dry Processing

1. Dig raw clay and spread it in the sun to dry completely (1-3 days).
2. Break dried clay into small chunks (fist-sized or smaller).
3. Crush chunks into powder using a rock on a flat stone surface.
4. Sift the powder through a woven screen or basket to remove stones and debris.
5. Add water gradually, mixing until you reach a thick, workable consistency (like bread dough).

Method B: Wet Processing (Slaking — Better Quality)

1. Break raw clay into fist-sized chunks.
2. Place in a container and cover with water (2 parts water to 1 part clay).
3. Let it soak for 24-48 hours, stirring occasionally. Clay breaks down into a smooth slurry.
4. Pour the slurry through a screen or loosely-woven fabric into a second container. Rocks, roots, and large grit stay behind.
5. Let the strained slurry settle for 24 hours. Heavy sand sinks to the bottom first.
6. Carefully pour or scoop the top layer of clay slip (the good stuff) into a separate container, leaving the sandy bottom layer behind.
7. Let the clay slip dry on a flat, absorbent surface (wooden boards work well — wood absorbs water from the clay) until it reaches a workable consistency.

Adding Temper

Pure clay cracks when it dries and explodes when fired because water cannot escape fast enough. You must add temper — a material that opens up the clay body and allows even drying and heating.

Common temper materials:

• Sand: The most common. Add 15-25% by volume. Use fine sand, not coarse.
• Grog: Crushed fired pottery. The best temper. Grind old pottery to a coarse powder and add 15-20%.
• Crushed shell: Works well. Adds calcium. 10-15%.
• Chopped plant fiber: Grass, straw, or hair. Burns out during firing, leaving tiny channels for steam to escape. 5-10%.

Mix temper thoroughly into the clay. The final mix should feel like firm bread dough — smooth, plastic, and not sticky.

Wedging (Kneading)

Before building anything, wedge (knead) your clay for 5-10 minutes. This serves two purposes:

1. Distributes moisture evenly throughout the clay body
2. Removes air bubbles (trapped air expands during firing and explodes the piece)

Technique: Push the clay forward with the heel of your palm, fold it back toward you, rotate 90 degrees, and repeat. Like kneading bread. Continue until the interior is smooth and uniform when you cut the ball in half with a string.

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Step 3: Hand-Building Techniques

Pinch Pot (Simplest Method)

1. Roll a ball of clay the size of your fist (about 8-10 cm diameter).
2. Press your thumb into the center, stopping about 1 cm from the bottom.
3. Pinch between your thumb (inside) and fingers (outside), slowly rotating the ball as you work.
4. Gradually thin the walls to 6-8 mm thickness, working from the bottom up.
5. Keep the rim even by trimming with a sharp shell or stone.
6. Smooth the surface with a wet finger or damp piece of leather.

Pinch pots are limited in size (usually under 15 cm diameter) but are excellent for cups, small bowls, and learning clay handling.

Coil Building (Most Versatile)

Coil building can produce vessels of any size, from small cups to storage jars 60+ cm tall.

1. Make a base: Roll a ball of clay and flatten it into a disc 8-10 mm thick. This is the bottom of your pot. Place it on a flat surface (a piece of bark or flat stone that you can rotate).

2. Roll coils: Take a lump of clay and roll it between your palms and the work surface into a rope about 1.5-2 cm thick and as long as you can manage. Consistent thickness matters — thin spots are weak spots.

3. Attach the first coil: Score (scratch with a tool) the top edge of the base disc. Wet the scored surface slightly with slip (clay dissolved in water to cream consistency). Place the coil on the scored edge and press it firmly into place. Score and slip every joint — this is the single most important step for preventing cracks.

4. Build up: Add coils one on top of another, scoring and slipping each joint. For a straight-sided pot, stack coils directly above each other. For a wider pot, place each coil slightly outward. For a narrowing pot, place each coil slightly inward.

5. Smooth the walls: After every 3-4 coils, smooth the inside and outside with your fingers, a wet sponge (use a wad of wet moss), or a smooth stone. Work the coils into each other so no gaps remain. Aim for 6-10 mm wall thickness.

6. Slow down at the top: As you approach the rim, the pot becomes top-heavy and fragile. Let the lower portion firm up for 30-60 minutes before adding the final coils.

7. Finish the rim: Roll a final coil slightly thicker and attach it carefully. Smooth it into a rounded, even lip. An uneven rim is the first thing you notice on a bad pot.

Slab Building (For Flat-Sided Objects)

1. Roll out clay into flat slabs 8-10 mm thick using a smooth stick as a rolling pin. Place thin sticks on either side as thickness guides.
2. Cut slabs to size with a sharp tool.
3. Let slabs firm up for 15-30 minutes until they are “leather-hard” — firm enough to handle without deforming but soft enough to join.
4. Score and slip all edges that will be joined.
5. Press edges together and reinforce the inside of each joint with a thin coil of clay smoothed across the seam.
6. Smooth all surfaces.

Slab building is ideal for: rectangular boxes, plates, tiles, lids, and oil lamps.

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Step 4: Drying

This is where most beginners fail. Pottery that dries too fast or unevenly cracks and is ruined.

Rules for drying:

• Dry slowly. Cover freshly built pieces with a damp cloth for the first 24 hours.
• After 24 hours, uncover but keep in shade with good airflow for 3-7 days.
• Never dry in direct sun or near a fire until the piece is bone-dry.
• Thick and thin sections dry at different rates and crack at the boundary. Keep wall thickness as uniform as possible.
• Turn pieces every day so all sides dry evenly.
• A piece is bone-dry when it feels room temperature to the touch (wet clay feels cool), is lighter in color, and is noticeably lighter in weight.
• Bone-dry (unfired) pottery is called “greenware.” It is fragile and water-soluble. Do not use it yet.
• Minimum drying time: 1 week for small pieces, 2-3 weeks for large pieces.

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Step 5: Firing

Firing transforms fragile, water-soluble greenware into hard, permanent ceramic. The key is raising the temperature slowly and evenly.

Temperature Stages

Temperature	What Happens
100°C (212°F)	Remaining free water evaporates. If heated too fast, steam explodes the piece.
200-300°C	Chemically bonded water begins to leave the clay structure.
573°C (1,063°F)	“Quartz inversion” — quartz crystals in the clay suddenly expand 2%. Most kiln explosions happen here. Must heat slowly through this range.
600-700°C	Clay becomes permanently hard (ceramic). Irreversible.
800-900°C	Stronger ceramic. Good for most functional pottery.
1,000-1,100°C	Clay begins to vitrify (become glass-like). Waterproof without glaze.

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Method 1: Pit Firing

The oldest firing method. Simple, requires no permanent structure, achieves 600-900°C.

Step 1 — Choose a dry, flat area at least 3 meters from any structure or flammable material. Dig a pit 60-90 cm deep and wide enough to hold your pottery with 15-20 cm of space between pieces and the pit walls. Round or oval pit shape works best.

Step 2 — Line the bottom with a 10 cm layer of dry kindling, straw, or wood shavings.

Step 3 — Place your bone-dry pottery in the pit. Nestle pieces in the kindling but do not let them touch each other. Space them at least 5 cm apart for heat circulation.

Step 4 — Cover the pottery with more kindling and wood shavings, filling all gaps.

Step 5 — Stack dry hardwood fuel on top, starting with small pieces and building up to wrist-thick pieces. Total fuel should fill the pit to ground level or slightly above.

Step 6 — Light the fire from the top. Resist the urge to light from the bottom — top-down lighting heats the pottery more gradually, reducing thermal shock.

Step 7 — Let the fire burn down completely. Do NOT add more fuel or disturb the fire. Total burn time: 3-6 hours.

Step 8 — Let the pit cool completely — at least 12 hours, ideally 24. Do not remove pieces early. Thermal shock from sudden cooling cracks pottery just as easily as heating too fast.

Step 9 — Remove pottery carefully. Expect 10-30% breakage rate on your first firings. This is normal. Broken pieces make excellent grog for your next batch.

Pit firing characteristics: Variable results, uneven coloring (often beautiful mottled patterns), temperatures of 600-900°C, pottery is functional but slightly porous.

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Method 2: Simple Updraft Kiln

A permanent firing structure that gives you higher temperatures (900-1,100°C), more consistent results, and lower breakage rates. Worth building once you are producing pottery regularly.

Building the Kiln

Step 1 — Build a circular base from stone or adobe bricks, 60-90 cm in diameter and 30 cm tall. Leave a firebox opening on one side, about 20 cm wide and 20 cm tall, at ground level.

Step 2 — Place a grate across the top of the base. This can be made from thick clay bars (3-4 cm diameter, fired if possible) laid across the opening with 2-3 cm gaps between them, or flat stones with gaps. The pottery sits above this grate; the fire burns below.

Step 3 — Build the kiln walls above the grate, continuing the circular shape upward for 60-90 cm. Taper slightly inward as you build (dome shape). Leave a small opening at the top for draft, about 15 cm diameter.

Step 4 — Build a chimney cap — a removable flat stone or clay disc for the top opening. This lets you control airflow during firing.

Firing the Kiln

Step 1 — Load pottery onto the grate, spaced 5 cm apart. Larger pieces on the bottom, smaller on top.

Step 2 — Start a small fire in the firebox using only kindling. Burn gently for 1-2 hours. This pre-heats the pottery slowly, driving out any remaining moisture.

Step 3 — Gradually increase fire size over the next 2-3 hours, adding progressively larger pieces of wood. The goal is to raise temperature steadily, not blast it with heat.

Step 4 — At full temperature (6-8 hours into firing), the inside of the kiln should be glowing orange-red. Maintain this for 1-2 hours by adding fuel steadily.

Temperature indicators (no thermometer needed):

• Dull red glow visible in dim light: ~500-600°C
• Cherry red glow visible in daylight: ~700-800°C
• Bright orange glow: ~900-1,000°C
• Yellow-white glow: ~1,100°C+ (maximum for most clay bodies)

Step 5 — Stop adding fuel and close the firebox opening with a stone. Close or partially cover the top opening. Let the kiln cool for 24-48 hours.

Step 6 — Open the kiln and remove pottery. Kiln-fired pottery should ring with a clear, bell-like tone when tapped. A dull thud means it was underfired.

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Glazing Basics

A glaze is a thin layer of glass fused onto the pottery surface during firing. It makes pottery fully waterproof, easier to clean, and more durable. Glazing requires higher temperatures (900-1,100°C) and specific mineral ingredients.

Simple Ash Glaze

The most accessible glaze for a survival situation:

1. Collect wood ash from hardwood fires (oak, ash, maple — not pine or softwoods).
2. Sift the ash through a fine screen to remove charcoal.
3. Mix 60% ash with 40% fine clay by volume. Add water to make a thin, paint-like slurry.
4. Apply to bone-dry or bisque-fired pottery by dipping, pouring, or brushing. Aim for a coating about 1 mm thick.
5. Let dry completely.
6. Fire to 1,000-1,100°C in the kiln.

The ash glaze will melt and form a glassy coating. Color varies from green to brown to tan depending on the ash source and clay body.

Salt Glaze (Advanced)

During peak firing temperature, throw handfuls of salt (sodium chloride) into the kiln firebox. The salt vaporizes and reacts with the clay surface to form a thin, bumpy, orange-peel-textured glaze. Warning: salt glazing releases hydrochloric acid fumes — only do this outdoors with wind blowing away from people.

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What to Make First

Prioritize these items in order of usefulness:

1. Water storage jar (coil-built, 20-30 cm tall) — stores clean drinking water
2. Cooking pot (coil-built, wide mouth, 15-20 cm tall) — boiling, stewing, making broth
3. Bowls (pinch or coil, 12-15 cm diameter) — eating and food prep
4. Cups (pinch pots, 8-10 cm) — drinking
5. Oil lamp (slab-built, shallow dish with a pinched spout for a wick) — light
6. Storage jars with lids — grain, seeds, dried herbs
7. Tiles (slab-built, 15 x 15 cm, 1 cm thick) — roofing, flooring, drainage

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Common Mistakes

Mistake	Why It’s Dangerous	What to Do Instead
Not wedging the clay	Trapped air bubbles expand during firing and explode the piece	Wedge for 5-10 minutes; cut in half to check for bubbles
Walls too thick or uneven	Thick sections trap moisture; explosion during firing	Aim for 6-10 mm uniform thickness throughout
Skipping score-and-slip	Joined sections separate during drying and firing	Always scratch and wet every joint; reinforce with coil
Drying too fast	Uneven shrinkage causes cracking	Cover for first 24 hours, shade-dry for 1-3 weeks
Firing too fast	Steam explosion under 200°C, quartz inversion explosion at 573°C	Spend the first 2 hours on a small, gentle fire
Removing from kiln too early	Thermal shock cracks the piece	Wait at least 12-24 hours after the fire dies
No temper in the clay	Pure clay shrinks excessively and cracks	Add 15-25% sand or grog by volume
Using wet or under-dried pottery in the kiln	Guaranteed explosion, can damage other pieces nearby	Piece must be bone-dry — light color, cool to touch, light weight

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What’s Next

Pottery opens the door to:

• Glassmaking — same kiln technology, higher temperatures, with silica sand
• Lime and Cement — kiln-fired limestone becomes quicklime, the basis of morite and concrete
• Food Processing — pottery vessels enable boiling, brewing, oil storage, and fermentation

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Quick Reference Card

Pottery & Ceramics — At a Glance

Finding clay: River banks, eroded hillsides, under topsoil. Pinch test — smooth, plastic, holds shape.

Processing: Slake in water → strain → settle → dry to working consistency → add temper (15-25% sand or grog) → wedge 5-10 min.

Building techniques:

Technique	Best For	Max Size	Difficulty
Pinch	Cups, small bowls	15 cm	Easy
Coil	Pots, jars, any size	Unlimited	Medium
Slab	Tiles, boxes, plates	Flat items	Medium

Drying: Cover 24 hours → shade-dry 1-3 weeks → bone-dry = light, cool, light-colored.

Firing temperatures:

• 600-700°C: Minimum functional (porous)
• 800-900°C: Good functional pottery
• 1,000-1,100°C: Vitrified, waterproof

Score and slip every joint. No exceptions.

Expect 10-30% breakage on early firings. Save broken pieces for grog.