Pottery and Ceramics Level 2

Who it is for. People who have finished Pottery and Ceramics (Level 1), or who already make pots and can show the same skills. At National Proficiency II, learners do a range of mostly routine work with limited supervision, and the level leads on to National Certificate I.

Bridge from Level 1: what you already know

Level 2 builds on each of these. If any feels weak, ask your trainer for a refresher session before Unit 1.

How the module works

Each unit has learning outcomes, performance criteria, the range and the evidence your assessor needs. You are judged Competent or Not Yet Competent. About 70% of the time is practical.

• Steps are numbered. A line ending with a source name comes from the sources list. A step with no source is standard safe practice or the author's teaching advice.
• Any number marked example is made up for practice. Replace it with local prices.
• Every unit ends with a Check yourself of three questions. Answers are in the Teacher Copy.

Competency standard

Range. Two clays; three test recipes; a 25 kg batch of the chosen body. Evidence. Body test record; batch record; observation of grog making and reclaim.

What a clay body is

A clay body is the mix you make pots from: one or more clays plus sand, grog or other additions. There are three kinds of additions: other clays, organic materials and sands. Sand reduces shrinkage, helps even drying and makes clay less sticky. Grog reduces cracking, protects pots against sudden heat and lets gases escape; about 20% grog is often added to crude clay. Quartz and grog both reduce drying shrinkage.

A good body for open-fired and Better Bonfire pots: shrinks little (10% or less when dried), bends into a coil ring without cracking, throws or coils easily, and survives the fire.

Step 1: blend by weight, not by eye

Tools: kitchen scale (to 10 kg); buckets; a notebook; labels.

1. Prepare each clay as slip (Level 1: soak, sieve, settle).
2. Decide a trial recipe, for example (example): Clay A 60%, Clay B 20%, grog 20%.
3. For a 10 kg dry batch: weigh 6 kg of Clay A, 2 kg of Clay B and 2 kg of grog (or measure the slips by known weights after drying samples).
4. Mix the slips together in one bucket, stir, sieve through fine mesh, and stiffen as in Level 1.
5. Label the bucket with the recipe and date.
6. Wedge well before use.

Step 2: test the body

Make three test bars of each recipe: 100 mm long, about 20 mm wide and 10 mm thick. Mark two lines exactly 100 mm apart with the needle tool.

Good clay should not shrink more than 10% in drying. Drying shrinkage of commercial earthenware clays is often listed around 3 to 6%, plus a few percent more in firing (example figures from supplier sheets; your clay will differ). Water absorption shows how porous your fired clay is: low absorption suits water pots that must not leak; higher absorption suits pots that cool water by sweating, or flower pots that breathe. There is no single right number at this level: compare recipes and keep the one that works best for the product. (Absorption method: general laboratory practice, author's description.)

Step 3: make grog safely

Grog is fired pottery crushed to powder. Broken pots from your own firings are free grog.

1. Wet the shards first, or crush them inside a closed sack laid on the ground. Dry crushing makes silica dust.
2. Pound them in a mortar (an old wooden mortar used only for grog) or with a heavy pestle in the sack.
3. Wear a rated dust mask (N95/FFP2 or better) and goggles while crushing.
4. Sieve the crushed grog through window mesh. Use the fine powder in bodies for throwing and the coarser grains for big coil pots and liners.
5. Store grog damp in a covered bucket.
6. Wash down the crushing area with water when you finish.

Step 4: reclaim scraps

Trimmings, failed pots (before firing) and slop from the wheel are good clay. Never let them dry in a heap.

1. Collect all scraps into a "reclaim" bucket during the day (this also stops dust).
2. Let them dry out completely in the bucket or in the sun (dry clay soaks better).
3. Cover with water and leave a day to slake.
4. Stir, sieve, stiffen on sacks or a dry clay bed.
5. Wedge thoroughly and label it "reclaim" with the body recipe.

Check yourself: Unit 1

1. Why do you blend by weight?
2. How do you measure water absorption?
3. Why do you wet shards before crushing them into grog?

Competency standard

Range. At least 10 cylinders and 10 bowls from 0.5 to 1 kg of clay. Evidence. Cut-in-half cylinders; trimmed bowls; observation.

The potter's wheel

Throwing means shaping a ball of clay on a turning wheel-head; it can only make round shapes. Early fast wheels were kicked to keep them turning, and kick wheels are still used today; electric wheels have a foot pedal for speed. In Sudan, potters use a wheel turned with the foot at a steady speed, with a metal disc (the wheel bat) on top. Vume potters have asked for potter's wheels to modernise their work.

Kick wheel or electric? A kick wheel needs no power and can be built by a carpenter or welder, but it is tiring. An electric wheel is easier but needs steady power and costs more. Prices for either in Ghana were not verified: get three quotes.

Set-up

The six steps of throwing

The main steps are to centre the clay, open a hole leaving a base, and raise and shape the walls.

1. Fix the clay. Pat the ball into a cone. Throw it down hard onto the centre of a damp (not wet) wheel-head. Press the edges down so it sticks.

2. Centre. Wet the clay. Turn the wheel fast. Brace your elbows on your thighs. Press the clay with both hands toward the centre and down. Push it up into a cone, then down again (do this two or three times). The clay is centred when it runs true and your hands feel no wobble. A Sudanese potter checks by moving a thumb across the top: no more friction means it is centred.

3. Open. Find the centre with your thumb, then press your fingers down into the centre to make a hole. Stop about 1 cm from the wheel-head (check with the needle tool pushed straight down). Pull the opening out to make a flat base the width you want.

4. Pull up the walls. Slow the wheel to medium. With one hand inside and one outside, squeeze gently at the bottom and lift slowly to the top in one steady movement. The walls are pulled up and made thinner by pressure between the hands. Do three or four pulls. Aim for walls about 6 to 8 mm even from bottom to top.

5. Shape. For a bowl, press gently outward from inside. For a narrow neck, collar (squeeze inward with both hands round the outside). Smooth with a rib. Compress the rim with a wet sponge or a strip of leather.

6. Cut off. Stop the wheel. Pull the cutting wire tight under the pot, flat on the wheel-head. Lift the pot with dry hands, or lift the bat. Sudanese potters remove the pot by hand or with a knife and leave it in the sun for half an hour to an hour to firm up. In a hot place, keep it in the shade and cover it loosely.

Trimming a foot ring

When the pot is leather-hard, it can be trimmed on the wheel to remove extra clay.

1. Turn the pot upside down on the centre of the wheel-head. Fix it with three small lumps of soft clay.
2. Turn the wheel at medium speed.
3. Hold the loop tool firmly with both hands braced.
4. Trim the base and outside wall to match the inside shape (tap: a hollow sound means it is thin enough).
5. Cut a foot ring about 5 mm high.
6. Sign and date the base.

Common throwing faults

Check yourself: Unit 2

1. How do you know the clay is centred?
2. How thick should the base be before you pull the walls?
3. When do you trim a foot ring?

Competency standard

Range. Three water pots; five grinding bowls; ten liners; one cooler set. Evidence. Measured pieces; size record; observation.

Traditional forms in Ghana

Ghana's potters make pots for water, cooking, serving and grinding, and for ceremonies; Mpraeso pots are used for many household tasks and at funerals. Tanoso potters make bowls in black and light brown for serving food and grinding vegetables and spices. Write down the names and uses of pots in your own area: they are your product list.

Making to a size

1. Agree the size with the buyer: height, width, rim width, and for liners the stove it must fit.
2. Weigh the clay for each piece the same (for example 2.0 kg per bowl).
3. Use a gauge. On the wheel, fix a stick or bent wire beside the wheel so its tip marks the height and width. For coil pots, cut a card or plywood profile template of the outside shape and hold it against the pot as you build.
4. Allow for shrinkage. If your body shrinks 10% in all, a pot must be made about 11% bigger than the finished size (finished size ÷ 0.9).
5. Measure every piece and record it. Reject or rework any that are more than 5 mm off (author's rule for this course).

Water storage pot

1. Coil or throw-and-coil: throw the bottom half on the wheel, let it stiffen, then add coils for the shoulder and neck (Sudanese potters build big zeer pots in stages this way, letting each stage firm up in the sun for half an hour to an hour before adding more clay).
2. Make the wall 10 to 12 mm, the shoulder round, and the neck narrow enough for a lid or a cloth.
3. Make a thick, rolled rim: water pots are lifted by the rim.
4. Burnish the outside top half if the buyer wants a finish; leave the lower part plain so the pot can "sweat" and keep water cool.
5. A zeer pot cools water because water that seeps to the outside evaporates and carries heat away.

Grinding bowl

1. Throw or press-mould a wide, low bowl with a thick base (about 2 cm) and walls 12 to 15 mm.
2. At leather-hard, comb the inside: cut criss-cross grooves about 2 mm deep with a comb made from a strip of wood with notches, or a fork.
3. Trim the outside smooth and keep the base flat so it does not spin while grinding.
4. Burnish or slip the outside only.
5. Fire well: a grinding bowl must be hard. Do the ring test and a scratch test.

Coal-pot liners (charcoal stove liners)

The ceramic liner inside an improved charcoal stove saves up to 50% of the charcoal. In Sudan, the Mubkhar charcoal stove is made on a mould, with the charcoal on a grill at the top so ash falls to the bottom; clay keeps it hot after the charcoal is used. In Kenya, the clay liners of the Upesi stove are thicker than pots and need a longer firing: 600 to 700 °C held for two to three hours.

Make liners only to a buyer's pattern. A stove maker gives you the size, the grate hole pattern and the number. Do not invent a stove design and sell it as "fuel-saving" without tests.

1. Get a sample liner or a drawing from the buyer.
2. Make a mould the right size plus shrinkage (a fired-clay hump mould, or a plaster mould made by your trainer).
3. Use a coarse body with grog and sand: liners must survive heat again and again.
4. Roll a slab about 20 to 30 mm thick (as the buyer specifies), press it on the mould, trim.
5. Cut the air holes or grate holes with a template while leather-hard.
6. Dry very slowly: thick pieces crack if dried fast.
7. Fire as long as the kiln allows (Unit 4).
8. Measure every liner against the buyer's gauge before delivery.

Pot-in-pot cooler (clay refrigerator)

A lidded clay pot sits inside a bigger pot with a layer of wet sand between them. Water evaporating from the outer pot carries heat away and cools the inner pot; water is added to the sand about twice a day. In Sudan, tests showed tomatoes kept fresh for about 3 weeks and okra for about 2 weeks, and a women's association sold over 50 coolers in 2007.

1. Make two pots on moulds or by coiling: an inner pot with a wall about 10 mm and a thick rim, and an outer pot big enough to leave a gap of about 4 to 5 cm all round for sand (the Sudan manual puts about 5 cm of sand under the inner pot).
2. Make a lid for the inner pot.
3. Fire both.
4. To assemble: about 5 cm of sand in the outer pot, stand the inner pot on it, fill round it with sand, wet the sand, and cover the inner pot with a damp cloth; a stand under it helps air flow.

Check yourself: Unit 3

1. Why must you make a pot bigger than the finished size?
2. Why does a liner need a coarse body and slow drying?
3. How does a pot-in-pot cooler keep food cool?

Competency standard

Range. One kiln built by the group; at least two kiln firings. Evidence. Site plan; build photos; firing logs; loss records.

Why a Better Bonfire kiln

Kenyan women potters firing stove liners in bonfires lost as many as 40% or more to cracking. Intermediate Technology Kenya designed the Better Bonfire kiln from local bricks with a mud dome: it holds in heat so it uses less fuel, heats and cools slowly so fewer than 10% crack, spreads heat more evenly, and is cheap and easy to build and maintain. The big kiln holds up to 120 stoves; a small one holds about 30.

Choose the site

• Good drainage, ideally a little above the ground around it, so it is not under water in the rains.
• Space round it for stacking pots and storing fuel.
• A safe distance from houses, thatched roofs and stored firewood, because smoke and sparks come out during firing.
• A simple shelter roof over the kiln protects it from the weather.

Materials (big kiln, as used in Kenya)

Fired clay building bricks (the table lists about 400 large and 100 small), a heavy polythene sheet, hard stones that do not soak up water, murram, sand, anthill soil or building earth, and about 500 litres of water; optional reinforcing rod, tie wire and chicken wire. Tools: rammer, pick, tape, builder's line, mason's hammer, spade, wheelbarrow, plumb line, spirit level and trowel. Brick sizes in Ghana differ: count again for your bricks.

Build it (summary of the Kenyan steps)

1. Foundation. Mark a circle 220 cm across. Dig it at least 50 cm deep. Put 5 cm of sand, lay the polythene for damp-proofing, more sand, then fill with hard broken stone, a layer of chippings or broken pottery, and rammed murram, level and just above ground.
2. Mortar. One part sand, two parts murram, one part anthill soil, with water to a thick, sticky mix. Do not use cement: it cracks in the heat.
3. Fireboxes. Mark the inner circle 150 cm across. Lay the outer ring of bricks. Build six firebox walls to make five channels about 18 cm wide, with 10 cm ventilation gaps in the second course; firebox channels are about 30 cm high.
4. Wall. Support the bricks over the firebox doors with a steel frame or fired clay plates, then build the circular wall to 75 cm high. The wall must be at least 10 inches (about 25 cm) thick.
5. Plaster. After at least 3 days, plaster the outside with equal parts sand and good clay, under 1 cm thick. If the bricks are poor, plaster the inside with equal parts grog, ash and clay.
6. Dry. Let the kiln dry for at least 28 days, then finish drying with small fires.

Load and seal

1. Sun-dry every pot for at least one day. Do not fire cracked or badly made pieces; break and reclaim them.
2. Put the first layer on the firebox bricks, then pack the rest tightly so nothing can move; do not stack in neat columns. Load above the wall to form a dome.
3. Fill gaps in the top layer with broken pottery. Spread 2 to 5 cm of dry grass or straw over the top.
4. Mix equal parts earth, cow dung and sieved ash with just enough water to spread without dripping, and plaster it over the grass to make a sealed mud dome.

Fire it

The temperature should rise slowly for two to three hours, then stay steady for about six more hours; about nine hours in all is recommended.

1. Light three fireboxes first (the two ends and the centre), from the side the wind comes from. The unlit ones act as chimneys.
2. Feel the dome for cool areas; poke small holes with a stick to draw heat there, and fill them later if they draw too much.
3. Feed wood steadily. After about two hours, light the other two fireboxes.
4. Repair cracks in the dome with mud. In strong wind, close firebox doors on that side with bricks.
5. After about eight hours, look through the firebox doors: if the bottom pieces are glowing, firing is nearly done.
6. Spread the embers along each firebox and close all doors with bricks and mud.
7. Cool for 20 to 24 hours. Keep repairing dome cracks. Opening too early cools pots too fast and breaks them.
8. Remove the dome and unload carefully. After each firing, inspect for sinking bricks, loose joints and cracks, repair them, and re-plaster regularly.

Firing log

Troubleshooting (from the Kenyan manual)

Check yourself: Unit 4

1. Why must you not use cement mortar in the kiln?
2. How long should a Better Bonfire firing last, and how long should it cool?
3. How do you draw heat to a cool part of the dome?

Competency standard

Range. Three slip colours; five decorated pots; ten test tiles. Evidence. Decorated and burnished pots; test tile board; observation; oral questions.

Slips and decoration

Slip is a mix of clay and water with no fixed ratio; it is used to decorate wet or leather-hard clay by dipping, painting or pouring, and pottery decorated this way is called slipware. An engobe is a related coating of clay, flux and fillers used to hide the colour of the body below.

Making coloured slip

1. Choose a clay that fires to a different colour (white, red, dark). Test-fire it first.
2. Dry it, break it up, soak it.
3. Sieve twice through fine mesh.
4. Adjust to thick cream for dipping, or thin cream for brushing.
5. Label the bucket with colour and source.

Ways to use slip

Burnishing to a standard

Burnishing gives a shine without glaze, at leather-hard; burnished pots are fired below about 1,000 °C. Polishing partly dried wares gives a better shine, but those wares are very fragile.

The standard you must reach: an even sheen over the whole burnished area; no scratch lines, no dull patches; no thumb marks; edges and rims polished too. Check in daylight from two angles.

Black pots. Tanoso bowls are sold in black and light brown. Black surfaces are usually made by smoke in the fire (smothering the hot pot in sawdust or leaves so smoke soaks into the clay); this is common potters' practice and is not covered by a source in this book. Test it with your trainer on spare pots first.

Glazes: what they are and the rules

A glaze is a glassy coating fused onto pottery; it makes the pot hold liquids and gives a hard, easy-to-clean surface. Its main parts are silica (the glass), fluxes (to melt it at lower heat) and alumina (to stop it running). A frit is glaze material melted into glass, cooled and ground again, which makes some toxic or soluble materials safer to use.

Lead. Lead oxide is an old flux because it melts at low heat. Acid foods and drinks can leach lead and cadmium out of poorly made or poorly fired glazes. Pots fired in an old kiln once used for lead glazes can be contaminated even with lead-free glaze, and bright orange, red or yellow decoration may contain lead pigments.

Heat. Earthenware glaze is fired at about 1,020 to 1,180 °C, after a first (bisque) firing at about 960 to 1,000 °C. An open fire or a Better Bonfire kiln does not reliably reach or hold these temperatures. So you will not glaze pots for sale at Level 2. Glazing in a proper kiln is Level 3.

Buying lead-free glaze in Ghana. No Ghana supplier of lead-free pottery glaze was verified for this book. Ask your trainer, a ceramics department (Ceramics is taught at NC I, NC II and HND levels, Source: CTVET CBT), or import a known brand. Keep the safety data sheet.

Glaze test tiles (with your trainer)

1. Make 10 flat tiles 5 × 10 cm from your body, with a hole at the top to hang them on a board. Bisque them (Level 3 kiln or a kiln your trainer can use).
2. Put on gloves, goggles and (for any powder) a mask.
3. Stir the lead-free glaze well.
4. Dip the lower two-thirds of each tile for 2 to 3 seconds; keep the back and edges clean, because the foot of a pot is always kept free of glaze so it does not stick in the kiln.
5. Label the back with an iron-oxide pencil or a scratched code.
6. Your trainer fires them in a kiln at the maker's temperature.
7. Hang the fired tiles on a board with notes: glaze name, thickness, temperature, result.

Check yourself: Unit 5

1. What is sgraffito?
2. Why are glazed pots not sold at Level 2?
3. Name three of the six glaze rules.

Competency standard

Range. Two full firings of the group's products. Evidence. QC sheets; grade counts; fault log; packing test.

Check at every stage

Grade standard (example)

Find the cause, not just the fault

When you find a fault, ask "why?" until you reach the cause, then write a fix in the fault log.

Packing and transport

1. Pack pots upright, rims up, with dry straw, grass, paper or old cloth between them.
2. Nest small pots inside big ones only if the rims do not touch.
3. Use crates, baskets or strong cartons; do not stack more than two layers of heavy pots.
4. Carry heavy pots with two people.
5. Count and check pots with the buyer on delivery; get a signed delivery note.

Products for sale

Water filters. Ceramic pot filters remove bacteria and larger germs by their tiny pores, but they do not reliably remove viruses or chemicals, and a cracked filter or dirty hands on the clean side can contaminate the water. Making filters needs a tested recipe, careful firing and flow-rate and water-quality tests; Pure Home Water's Ghana factory was set up for this work. At Level 2 you may resell filters from a known, tested maker, with the maker's instructions; you do not make or sell your own pots as filters.

Check yourself: Unit 6

1. Name three checks after firing.
2. What do you do with a grade C pot?
3. Why must you not sell your own pots as water filters?

Competency standard

Range. The trainee's own or a group business. Evidence. Costing sheet for three products; price list; order form; marketing plan.

Cost every product line

For each product, write: clay and additions per piece, fuel share per firing, labour, packing and transport, and firing and grading losses. Divide by the number of good pieces, not the number made.

Wholesale and retail

• Wholesale: bigger orders to nurseries, stove makers, traders. Lower price per piece, but fewer trips and steady work.
• Retail: single pots to homes and tourists at a stall or by WhatsApp. Higher price, more time selling.
• Order terms: a written order with product, size, number, price, delivery date and a deposit (for example 50%) before you start a big order.

Tanoso potters' buyers include traders from Côte d'Ivoire buying in bulk, and women traders selling along the highway. Vume pots sell in Accra, Tema, Koforidua and Aburi.

Location settings that give good returns

Business ideas and ingenuity

Market yourself

• WhatsApp Business: profile, catalogue with photos and prices, and quick replies.
• Google Business Profile so buyers find your yard on Maps.
• Samples: leave one flower pot with a nursery and one liner with a stove maker.
• Referrals: ask happy buyers to tell others; give a small discount for referrals.
• Your stamp: press a small clay stamp with your mark on every pot.
• Portfolio: photos with sizes, prices and the grade standard.

Working as a group

Sirigu's women potters built a group that trains women and markets their products. A group can share a kiln, clay digging and transport. Write down: who does what, how money is recorded, how profit is shared, and how new members join. Keep a cash book and a stock book (see the hub's Money Skills manual).

Accessibility

The Persons with Disability Act 2006 (Act 715) bans discrimination in employment and asks for accessible public places. Seated tasks suit many persons with disabilities: wedging small lumps, throwing on a wheel set at the right height (an electric wheel removes the kicking), coiling, trimming, decorating, burnishing, grading and selling. Kiln building, clay digging and carrying are better shared. A ramp, a wide path between tables, tools within reach, picture instruction cards and good lighting help. Ask each person what works for them. (Author's advice; no Ghana source found.)

Check yourself: Unit 7

1. Why do you divide costs by the number of good pieces, not pieces made?
2. What should a written order include?
3. Name two ways to market pots without paying for adverts.

1. Name three things you add to clay and why.
2. How do you work out water absorption?
3. Why must grog be crushed wet or in a closed sack?
4. What are the main steps of throwing?
5. How do you make pieces the same size?
6. How much bigger do you make a piece if the body shrinks 10%?
7. Why does a coal-pot liner need a long, slow firing?
8. Give four features of the Better Bonfire kiln.
9. Why is cement mortar not used in the kiln?
10. At what temperatures are earthenware bisque and glaze fired?
11. Name the three grades and what you do with each.
12. What can a ceramic water filter not remove?

Best next reads: A Better Bonfire Kiln (Intermediate Technology Kenya); Practical Action's Clay Based Technologies; HSE's ceramics silica sheets CR1 to CR5; the Hub's Money Skills and Workplace Safety manuals.

What this module does not cover: glaze firing in a kiln for sale, kiln design beyond the Better Bonfire, making water filters, running a workshop with staff, registration and bookkeeping (see Level 3).

Every source used in this manual is listed, with links, in the Teacher Copy.