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 about a third of them link to the lesson that goes into it properly. Five videos, and where our studio stands.

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

50Ways, and we have watched most of them happen in this building
19Of them cost the most pots here
19Ways 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 nineteen 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 videos 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 work through a mistake and then its fix puts 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: pulling, the wheel, 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 goes through five common beginner mistakes in nineteen minutes. Then come back to the list the next time a pot dies.

The whole idea

Nineteen of the fifty cost the most pots.

The other thirty-one matter too, and two of them matter for safety: a vent hole in any closed form, and sanding a fired foot wet, never dry, over a bucket, with safety glasses and an N95 or better. The nineteen below are the ones that cost the most pots, in the order they happen, each with its fix.

Stage one

Preparing the clay. Eight ways to start a pot already in trouble.

Preparing the clay.

Most of what goes wrong here shows up at the wheel, as a wobble or a wall that will not hold, and by then nobody remembers the wedging.

Most of what goes wrong here shows up at the wheel, and by then nobody remembers the wedging.

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. About thirty ram’s head pushes from a fresh bag, and a hundred or more for reclaim; 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. At home, each clay gets its own bucket. Here the barrels are mixed on purpose, so the rule is clay and water only, and a scrap you are not sure about goes in the trash.
5Clay that is too stiffYou cannot center what you cannot dent with a thumb. Stiff clay needs water and time: water in a sealed bag overnight, or slice the block, wet every face, stack it back up and wedge it an hour later. Water wedged straight into a stiff block only wets the skin. 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. Wet plaster, plaster dust and plaster damp boxes never come 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 three 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 floorAn S-crack is a drying crack: a floor that is wetter, thicker or looser than the wall dries later, and the two shrink out of step. Open the clay, sponge the puddle out of the bottom, then rib or finger the floor from dead center outward, three or four passes, so the floor keeps pace with the wall. 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 pushed through the floor, and the hole smoothed shut again, tells you the truth; about three eighths of an inch is plenty.
12Leaving the floor too thinThe opposite problem. A floor that is too thin leaves nothing to trim, and the trimming tool opens 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 your fingers inside and out as you pull, are what the pulling lesson is for.
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, because a puddle left in the bottom keeps the floor wet after the walls dry.
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. Run a chamois or a finger around the rim with the wheel slow after every pull, and again 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 five ways off the wheel, and you will mostly use two.

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 floorDo the needle test from way eleven before the trimming tool goes in, and close the pinhole after. A hole in the floor is a planter.
21Storing wet work on a wooden batWood draws water out of the base while the walls stay wet, so the base dries and shrinks first and cracks, and the wet 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. Shield the side facing the draft, turn the pot so every side gets the same air, and keep it out of the draft.
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 around it goes, and leaves its creases in the surface. 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 bag, tented off the clay and closed at the top.
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, a slab or a coil.

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. Take the slab roller down a little on every pass, never in one go, and finish with a pass both ways at the thickness you want.
33A coil pot built too fastTen coils in an hour on a base that is still soft slumps under its own weight. Build a few coils, let the wall firm up only until it holds its own weight, then score, slip and carry on before the top coil goes stiffer than the one you are adding. 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 three of them can fuse a pot to the shelf.

Glazing.

A glaze mistake can take somebody else’s pot with it.

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

35Glaze on the footIt fuses the pot to the shelf, and the shelf has to be ground or replaced. No glaze on the bottom quarter inch, and a damp sponge around the foot after glazing. Every piece goes on a kiln cookie, every time. It is one of the most expensive mistakes a beginner makes.
36Too many coatsThree is the standard for most brush-on glazes. Five coats run, and a run is a pot fused to a shelf. If you want it thicker, test it on a tile 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 bisque piece that was soaked, not flash rinsed, takes the glaze unevenly and blisters. Rinse it in and out in a second or two right before you glaze, and never let it sit in the water.
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 from the bottom, every time. If it looks too thick or too thin, ask an instructor, and never add water to a glaze bucket yourself.
43Moving a brush from one jar to anotherIt contaminates the second glaze for everybody, and you cannot see it. A brush never goes into a jar here: spoon a little glaze into a small cup, one glaze to a cup, and dip the brush in that. Wash the brush by hand, between every bristle, before it touches another glaze.
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 half of them happen after the firing.

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 bisqueWater left in the clay turns to steam in the bisque and bursts the piece, and it takes the pots around it with it. Bone dry means the base is room temperature against your cheek and the clay is pale all the way through, and thick work gets a few extra days because the cheek only reads the surface. The front desk is allowed to say no.
46A closed form with no holeA sealed hollow piece is a bomb, and steam is what loads it: water in the wall turns to steam in the firing and has to leave through the pot. Any enclosed shape gets a pinhole somewhere before it dries. Our enclosed forms lesson shows where.
47A lid fired on with no waxGlaze where the lid and the gallery touch melts and fuses the two into one object. Wax both contact surfaces so no glaze lands there, and the lid can then fire on the pot so they shrink together.
48Grinding or sanding a sharp foot dryDust from fired clay and glaze carries silica, and water is what keeps it out of the air. Smooth a fired foot wet, over a bucket, never dry, with safety glasses and a fitted N95 or better, never a paper dust mask. The rinse water goes into a bucket, and the fired grindings in it go in the bin, never down a sink or a drain. A power grinder or a rotary tool is a job for home, outdoors, with a face shield, and never at the studio tables. Our grinding lesson covers the tools and the mask.
49Putting a hot pot in cold waterA pot that comes out of a warm kiln and goes straight into cold water can crack with a ping. Our team unloads the kilns here, so this one is mostly for a kiln at home: let the piece come to 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. Almost every other time, the pot died one of the forty-nine ways above before it ever went in, and the kiln just revealed it. Look at the pot, find the way, and stop doing that one.

Watch it done

Now watch the mistakes happen, in five videos.

Watch this one, then pick your three.

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

Nineteen minutes on five mistakes most beginners run into. The other four videos are in the comprehensive version.

Start here: five common mistakes5 Mistakes Every Pottery Beginner MakesFlorian Gadsby
Nineteen minutes on five mistakes most beginners run into, taken one at a time: clay distribution, hesitating on the pull, forming the base, pulling up too fast, and a rim left too thin. Watch on YouTube
At the wheel, five mistakes and fixes5 Common Wheel Throwing Mistakes (And How to Fix Them!) | Pottery for BeginnersMW Ceramics
Twenty-three minutes on five wheel mistakes and the fix for each, from pulling walls too fast to an uneven rim, shown on the wheel. Watch on YouTube
Pulling a cylinder, and what goes wrongPulling for beginners (common mistakes)Earth Nation Ceramics
Eighteen minutes on pulling a cylinder, with chapters on hand position, water and keeping the pressure even. The maker asks you to watch their opening, centering and wedging videos first. Watch on YouTube
Eight more, at the wheelStop Ruining Your Pots! 8 Pulling Mistakes Every Beginner MakesMW Ceramics
Thirty-one minutes on eight pulling mistakes and the fix for each, from pulling too early to the idea that one way suits every pot. Hands and pressure come up here too, which is why we kept both. Watch on YouTube
Reading the crackStop cracks in your pottery! // Different kinds of ceramic cracks and how to prevent themPottery to the People
Eighteen minutes on the kinds of crack and what causes each, from S-cracks in the base to thermal shock, crazing and shivering. The one 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, unlabeled work, which is not one of the fifty. 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, which did not make the list of fifty. Between them they cost us more pots and more shelves than anything else on the list.

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 every other pot in that kiln.

The certifications

Dipping glaze, slab rollers and slab molds, brush-on glaze and raku each have a short course and a signed agreement, and a lot of what they ask about is on this list.

Firing fees

5 cents a cubic inch, with a flat $4.80 for 125 cubic inches or less, and bisque firings 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 thick and thin parts dry at different speeds, and that sits behind a lot of the cracks on the list.

My pot cracked. Which of the fifty was it?

An S-crack in the floor is way ten, eleven or fourteen, and all three come down to the floor drying later than the wall. 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 last video above, on reading a crack, covers S-cracks, thermal shock, crazing and shivering.

Was it the kiln?

Occasionally, and the studio will tell you when it was. Almost every other time the pot died one of the ways above before it ever went in, and the kiln just 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.