An illustration of a potter scratching her head at a workbench taped off with yellow caution tape, with cracked, collapsed and shattered pots marked by numbered evidence tags like a crime scene

Electives · The field guide to failure

Fifty easy ways potters mess up their own pottery.

Nobody breaks a pot on purpose. Pots break because of something small that happened days earlier, at a stage nobody was paying attention to, and by the time the damage shows up the moment that caused it is long gone. This is a list of those moments, in the order they happen, from the bag of clay to the shelf after the glaze firing. None of them is a mystery. Every one of them has a fix that takes less time than the pot took.

Fifty ways, grouped by stage: preparing the clay, at the wheel, trimming and drying, hand building, glazing, and the kiln and after. Each one is a sentence about what went wrong and a sentence about what to do instead, and most of them link to the lesson that goes into it properly. Five videos, and where our studio stands.

This is the short version: the sixteen ways that cost the most pots, each with its fix. The rest are in the comprehensive version.

50Ways, and every one of them has happened in this building
16Of them account for almost every pot that gets thrown away here
16Ways that cost the most pots, and the fix for each
x5Videos, from potters who do not work here
Jump to a section
Why this page has words and video The fifteen that cost the most pots Preparing the clay, ways 1 to 8 At the wheel, ways 9 to 18 Trimming and drying, ways 19 to 28 Hand building, ways 29 to 34 Glazing, ways 35 to 44 The kiln and after, ways 45 to 50 Five potters on the mistakes The one video to watch How it works at The Clay Hole Questions people actually ask Related lessons

All fifty, by stage, each with the fix, and five videos.

Read it, then watch it

Why this is written down and filmed, both.

A list is a list; it reads better than it films, and this one is meant to be scrolled on a phone at the wheel when a pot has just done something and you want to know which of the fifty it was. But a mistake in the making is a different thing from a mistake described, and watching a potter pull a wall the wrong way, then the right way, side by side, fixes the idea in your hands in a way a sentence cannot.

So read the list for the map of everything that can go wrong, and watch the videos for the handful of mistakes that need to be seen to be understood: centering, pulling, and cracks. Between the two you will recognize your own mistakes on sight, which is the whole game.

Use both, in this order

Skim all fifty once, fast. Then watch the first video, which is five of the fifty in eighteen minutes from a potter you will recognize. Then come back to the list the next time a pot dies.

The whole idea

Almost every pot that gets thrown away died one of sixteen ways.

Most of the fifty are rare or cosmetic. The sixteen below account for nearly every pot in the reclaim, in the order they happen, each with its fix. Stop doing these and the other thirty-four will hardly ever come up.

Stage one

Preparing the clay. Eight ways, and most of them are air.

Preparing the clay.

Everything that goes wrong here shows up as a bang in the bisque or a wobble on the wheel, and by then nobody remembers the wedging.

What goes wrong here shows up weeks later.

1Not wedging at allStraight from the bag is fine for a mug and a gamble for anything bigger. The bag has air pockets and uneven moisture in it, and both come out on the wheel. Sixty ram’s head turns; our wedging lesson shows the move.
2Wedging air inFolding clay over itself and slapping it shut traps air instead of pushing it out. That is kneading bread, not wedging clay. Roll and push; never fold and slap.
3Wedging on a wet canvasClay sticks, tears, and picks up crumbs from the last person. Scrape the canvas, let it dry, and wedge on a clean surface.
4Reclaim that is not the same clayPorcelain scraps in the stoneware bucket, grog in the smooth. The reclaim comes back short and speckled and nobody knows why. Each clay in its own bucket.
5Clay that is too stiffYou cannot center what you cannot dent with a thumb. Stiff clay gets a splash of water wedged in, or a night in a bag with a wet rag. Our stiff clay lesson is the method.
6Clay that is too softSoft clay centers easily and collapses at the third pull. Wedge it on a dry bat for ten minutes before you start, or throw something short.
7Plaster in the clayOne chip from a home slump mold or a damp box. It blows a crater out of the pot weeks after the firing. Plaster never comes into the building, and a scrap you are unsure of goes in the trash.
8Weighing nothingGuessing the ball size means every pot in a set is different before you have touched the wheel. A scale takes ten seconds and a set takes an evening.

Stage two

At the wheel. Ten ways, and half of them are the floor.

At the wheel.

These are the ones that feel like bad luck and are not.

These feel like bad luck. They are not.

9Never actually centeringClose enough is not centered. A pot thrown off center has a thick side and a thin side, and the thin side is where it cracks, warps and runs. Our centering lesson is the fix, and so is the kick wheel.
10Not compressing the floorThe single most common cause of an S-crack. Open the clay, then rib or finger the floor from the center outward with real pressure, twice. Our compressing lesson covers it.
11Leaving the floor too thickA thick floor dries days after the walls, and the difference is a crack. A needle tool through the floor tells you the truth; three eighths of an inch is plenty.
12Leaving the floor too thinThe other direction. The needle goes through, or the pot cannot be trimmed without a hole. Our too-thin bottom lesson is the rescue.
13Walls uneven from top to bottomA thick base and a thin rim dry at two speeds and shrink at two speeds. Even walls, checked with a needle, are the whole reason the pulling lesson exists.
14Too much waterEvery pass with a wet sponge is water into the wall, and a wet wall slumps, then cracks as it dries. Water only when the clay drags, and sponge the floor before you finish.
15Too many pullsEvery pull tires the clay. Three good pulls beat seven anxious ones. If it is not there after four, it was too tall for the weight.
16The rim never compressedA rim left raw splits as it dries and chips after firing. A chamois or a finger run round the rim with the wheel slow, every time, at the end.
17Wiring off with the wheel spinningThe wire drifts and the base goes concave or gets a hole. Wheel off, wire taut, one pull.
18Twisting the pot getting it offLifting a wet pot by the rim twists the walls and the twist appears as a spiral crack in the bisque. Our getting it off lesson has three better ways.

Stage three

Trimming and drying. Ten ways, and this is where most pots actually die.

Trimming and drying.

Nothing dramatic happens at this stage, which is why nobody is watching when it goes wrong.

Nothing dramatic happens here, which is why it goes wrong.

19Trimming too wet or too dryToo wet and the tool tears; too dry and it chatters and chips. Leather hard is when the pot holds its shape and takes a thumbnail mark without smearing. Our trimming lesson shows the test.
20Trimming through the floorThe needle test from way eleven, before the trimming tool goes in. A hole in the floor is a planter.
21Storing wet work on a wooden batWood pulls water out of the base at its own speed and the base cracks, and the bat warps. Plastic bats for storage, every time.
22Drying too fast on one sideA pot near a door, a vent, a window or a heat lamp dries one face and cracks or warps. Cover it, turn it, and keep it off the shelves by the door.
23Using the heat lamp to dry a finished pieceA skin over a wet core, and the crack comes days later. The lamps are for stiffening a collapsing wall for a minute, and our heat lamp lesson is the whole rule.
24Attaching a handle at the wrong stiffnessHandle and mug at different stiffness shrink at different rates and part company at the join. Both leather hard, scored, slipped, and a sheet over the mug. Our handles lesson covers matching them.
25Never turning it overThe base is the only part of a pot getting no air. Flip it the moment it can take its own weight, or the base is a week behind the rim.
26The bag pressed against the potPlastic lying on wet clay stops that patch drying while everything round it goes, and prints its weave. Tent it. Our sheets and bags lesson is the whole subject.
27Leaving it uncovered because you were coming backYou were not coming back. It is past leather hard now and the handle will not go on. Anything that has to wait more than two days goes in a closed bag.
28Calling it bone dry when it is coldA piece that feels cool against your cheek still has water in it, and water becomes steam in the bisque. Room temperature and pale all the way through, and a few more days if in doubt.

Stage four

Hand building. Six ways, and every one is a join or a slab.

Hand building.

Hand-built pots fail at the seams, and the seams fail because of what happened when they were made.

Hand-built pots fail at the seams.

29A join without scoring and slipPressed together and smoothed over looks fine and comes apart in the bisque. Score both sides, slip, press, and blend. Our scoring lesson is short and mandatory.
30Joining two different stiffnessesA fresh slab onto a leather hard one, or a soft coil onto a stiff pot. They shrink apart. Same stiffness, or the softer one stiffened first under a lamp for a minute.
31A slab rolled in one directionClay rolled only one way has a grain and warps along it. Turn the slab ninety degrees between passes. Our flat tiles lesson is the long version.
32Slabs of uneven thicknessThe thin part dries first and pulls the thick part out of true. Guide strips on the slab roller, or the same setting every pass.
33A coil pot built too fastTen coils in an hour on a base that is still soft slumps under its own weight. Build to a height, let it stiffen, build again. Our coil lesson paces it.
34Corners left thickA slab box with thick corners and thin walls cracks at the corners as they dry last. Bevel the joins, blend them thin, and dry it under a sheet.

Stage five

Glazing. Ten ways, and most of them are the foot.

Glazing.

A glaze mistake is the only one on this list that can take somebody else’s pot with it.

The only mistakes here that can take somebody else’s pot with them.

35Glaze on the footIt fuses the pot to the shelf, and the shelf is ground for an hour or replaced. No glaze on the bottom quarter inch, and a damp sponge round the foot after glazing. The single most expensive mistake a beginner makes.
36Too many coatsThree is the wall’s standard. Five runs, and a run is a pot fused to a shelf. If you want thick, tile it first.
37Too few coatsOne coat of most brush-on glazes is a wash. It looks dry and streaky and it was never going to look otherwise. Three coats, each in a different direction.
38Glazing over dustBisque that sat on a shelf for a month has a film on it, and glaze crawls off the film. Wipe the piece with a damp sponge, let it dry, then glaze.
39Glazing a piece that is still dampA rinsed bisque piece glazed ten minutes later takes the glaze unevenly and blisters. Let it dry overnight after any wiping.
40An untested combinationTwo glazes that each behave alone can run like water together. A tile first, on a catcher. Our test tile lesson is the method.
41Glaze inside a lid seat or a galleryThe lid fuses to the pot. Wax the gallery and the lid flange, and fire the lid on the pot only if both are bare where they touch.
42Dipping into an unstirred bucketDipping glaze settles. The first pot gets water and the fifth gets sludge. Stir it, every time, from the bottom; the certification says so because of the pots that came out of an unstirred bucket.
43A brush from one jar into anotherContaminates the second glaze for everybody, invisibly, for a month. One brush per jar, rinsed between.
44Thumbprints and drips left onA drip on the side fires as a lump, a thumbprint fires as a bare patch. Look at every pot in raking light before it goes on the glaze shelf.

Stage six

The kiln and after. Six ways, and you have finished the pot by the time they happen.

The kiln and after.

The last six happen after you have stopped thinking about the piece.

These happen after you have stopped thinking about the piece.

45Not bone dry into the bisqueIt explodes, and it takes the pots around it with it. Bone dry means room temperature against your cheek and pale all the way through, and the front desk is allowed to say no.
46A closed form with no holeA sealed hollow piece is a bomb. Any enclosed shape gets a pinhole somewhere before it dries. Our enclosed forms lesson shows where.
47A lid fired on with no waxThe lid and the gallery fuse into one object. Wax both contact surfaces, and the lid can fire on the pot so they shrink together.
48Grinding a sharp foot without a maskFired clay dust is silica. A fitted N95 or a half-face respirator for any sanding or grinding, and never a paper dust mask. Our grinding lesson covers the tools and the mask.
49Putting a hot pot in cold waterA pot out of a warm kiln into a sink cracks with a ping. Room temperature first. Same for a mug from the dishwasher onto a cold counter, and that one is your customer’s problem, so tell them.
50Blaming the kilnThe kiln fails sometimes and the studio will say so. The other ninety-five times, the pot died one of the forty-nine ways above, days before the firing, and the kiln just revealed it. Look at the pot, find the way, and stop doing that one.

Watch it done

Now watch five potters make the mistakes on purpose.

Watch this one, then pick your three.

None of these potters work here or know we exist. Between them they cover centering, pulling, and reading a crack after the fact. The still frames load while you read; the player and its cookies wait until you press play.

Eighteen minutes on the five mistakes almost everybody makes. The other four videos are in the comprehensive version.

Start here: five of the fifty, shown5 Mistakes Every Pottery Beginner MakesFlorian Gadsby
Eighteen minutes on the five mistakes almost everybody makes, from a potter who has taught thousands of people not to. Ways nine, ten, thirteen and twenty-eight are all here. Watch on YouTube
At the wheel, side by side5 Common Wheel Throwing Mistakes (And How to Fix Them!) | Pottery for BeginnersMW Ceramics
Twenty-three minutes of the wrong way and the right way, one after the other. The clearest video for stage two. Watch on YouTube
Pulling walls, every way it goes wrongPulling for beginners (common mistakes)Earth Nation Ceramics
Half a million people have watched this eighteen minutes because it shows every pulling mistake on this list happening to a real pot. Watch on YouTube
Eight more, at the wheelStop Ruining Your Pots! 8 Pulling Mistakes Every Beginner MakesMW Ceramics
Thirty minutes, and it overlaps with the video above on purpose. Watching the same mistake explained by two different potters is how it sticks. Watch on YouTube
Reading the crackStop cracks in your pottery! // Different kinds of ceramic cracks and what causes themPottery to the People
Eighteen minutes on which crack means which mistake. The companion to stage three, and the video to watch when a pot has already died and you want to know why. Watch on YouTube

How it works here

Which of the fifty we see most, and what the studio does about them.

This page is written for potters everywhere. Here is where our studio stands.

Three things to know here

The four we see most: glaze on the foot, not bone dry, a handle at the wrong stiffness, an unlabeled bat. The front desk can refuse a piece that is not bone dry. A pot that died in the kiln usually died days earlier, one of these ways.

The four we see most

Glaze on the foot, not bone dry, handles at the wrong stiffness, and unlabeled work. Between them they account for most of the pots in the reclaim and most of the shelves that get ground.

The desk can say no

A piece that is not bone dry does not go in the bisque, and the front desk is the one who decides. It is not personal. It is the twenty pots next to yours.

The certifications

Dipping glaze, slab rollers and slab molds, brush-on glaze and raku each have a short course and a signed agreement, and every question in every quiz is one of the fifty.

Firing fees

Five cents a cubic inch, $4.80 minimum, bisque free. A pot that dies in the glaze firing still cost the firing, which is one more reason to look at this list before it goes in.

The glaze problems page

When a glazed pot comes out wrong, the glaze problems lesson reads the symptom and names the way. It is stage five of this page in much more detail.

Nobody is keeping score

Every instructor here has done most of the fifty, and the ones who have not are lying. Bring the dead pot to show and tell; it teaches the room more than a good one.

Questions people actually ask

The ones that come up at the reclaim bucket.

Which mistake ruins the most pots?

Not bone dry into the bisque, because it takes other people’s pots with it. After that, glaze on the foot, because it takes the shelf. After that, uneven walls, because it causes half the cracks on the list.

My pot cracked. Which of the fifty was it?

An S-crack in the floor is way ten. A crack at a handle join is way twenty-four. A crack at the rim is way sixteen or twenty-two. A spiral crack is way eighteen. A crack across the base on a thick pot is way eleven. The cracks video below reads them all.

Was it the kiln?

Occasionally, and the studio will tell you when it was. Usually the pot died days before the firing, one of the ways above, and the kiln revealed it.

Which three should I fix first?

Whichever three you know you do. Everybody has favorites. Most people’s are uneven walls, drying too fast, and too many coats of glaze.

Are hand-built pots safer?

They fail differently, not less. Joins and slabs instead of floors and rims. Ways twenty-nine through thirty-four are the hand-builder’s list.

How do I know a piece is bone dry?

Room temperature against your cheek, not cool; pale and even all the way through, no darker patches at the base; and a few more days if you are not sure. Nothing bad happens to a piece that waits.

That is the list

Every pot that died had a reason. Now you have fifty of them.

The point of a list like this is not to make you careful; careful potters make stiff pots. The point is that when a pot fails, you can look at it and know which of the fifty it was, so the next one is not the same one. Everybody on this list has been here. The good potters are just the ones who stopped repeating their favorites.

If you want all fifty, the questions and the other four videos, switch to the comprehensive version at the top. Otherwise, pick the three of these you know you do, and stop doing them this week.

Back to Clay Hole University Glaze Problems, Causes and Fixes

Written for potters everywhere. Where our studio does things differently, the page says so.