Throwing techniques
Compressing the floor and the rim
Two moves. Maybe fifteen seconds of your life, total. Skip them and the pot looks perfect for three weeks and then splits open on a shelf while you are at work.
This is the least glamorous thing in throwing. Nobody films it. Nobody posts it. There is no satisfying moment where the clay does something beautiful. It is just you, pressing on a wet surface, on purpose, being boring for a few seconds at two specific points in the process.
And it is the single biggest reason pots survive.
It is also the single biggest reason pots survive. Here is the whole thing, stripped down.
Just want the checklist? It is down here.
Which version do you want to print?
Why this page is built this way
Read it, then watch it. In that order.
You could have searched this on YouTube and been watching somebody do it forty seconds ago. So it is fair to ask why we sat down and wrote all of this out instead.
Here is our honest answer, from watching a lot of people learn in this building.
Speed, angle, pressure
You cannot write down how fast a wheel is going or how hard somebody is pressing. You have to see it. Video shows you the actual thing, at the actual speed, with the actual amount of water flying around. Nothing on this page replaces that.
Why, and in what order
Video is a river. It moves at its pace, not yours. Words sit still. You stop on the one sentence that confused you, read it twice, and go on. You can also scan words, which you cannot do with a video.
The part that matters most
Watching feels like learning and mostly is not. You finish a video, your brain files it under done, and then you sit at a wheel and your hands have no idea what you just agreed to. Reading the same idea and then watching somebody do it gives you two separate handles on one thing. Two handles is a lot harder to drop than one.
This is our experience of teaching people, not a study we are citing. But we have watched it play out enough times that we build our guides this way on purpose.
There is one more reason, and it is completely practical. Your hands are wet. There is clay on your phone screen already, because there always is. You are not going to scrub a twenty-minute video back and forth with a muddy thumb looking for the eight seconds you actually needed. You are going to glance at a short list.
So the words come first, the videos back them up, and there is a stripped-down checklist near the bottom built for exactly that muddy-thumb moment. Read the page once at home. Keep the checklist open at the wheel.
What you are actually doing
Putting back together what your own hands pulled apart
Opening a pot drags the clay outward. Pulling a wall drags it upward. Both leave the clay looser than they found it, and compression is you pressing it back into contact.
Clay is not a smooth paste. It is billions of flat little platelets with water between them, stacked like a deck of cards that got dropped. When you drag your finger across wet clay, you drag those platelets along with it and open small gaps between them.
Opening a pot is one long outward drag across the floor. Pulling a wall is one long upward drag along the rim. Both moves are necessary and both moves leave the clay looser than they found it.
Compression is you pressing it back into contact. Firm, flat pressure on a surface you just stretched. That is the whole idea, and it is the same idea whether you are doing it to the bottom of a bowl or to the lip of a mug.
The two places that need it are the two places you dragged the hardest. The floor and the rim.
A cylinder sliced down the middle, sitting on the wheel head. The two terracotta arrows show the direction you press: down onto the rim, and outward across the floor. The five numbered markers match the list beside the drawing.
- The rim Slightly thicker than the wall right below it, and pressed after every single pull. It is the thinnest, most stretched, most abused part of the pot.
- The wall Gets gradually thinner as it rises. You do not compress this, it is drawn in so you can see the proportions the other two are supposed to match.
- The floor Roughly as thick as the base of the wall, and pressed flat from the middle outward. A floor much thicker than the walls is a drying problem all by itself.
- The inside corner Where the floor meets the wall. Slurry and water pool here, and it is the first place people stop pressing because it feels awkward to reach.
- Standing water Sponge it out before the pot leaves the wheel. A floor sitting in a puddle stays wet longest and shrinks last, which is the whole argument in one picture.
- The rim A little thicker than the wall below it. Compress after every pull.
- The wall Thins as it rises. Nothing to do here, it is the proportion the other two match.
- The floor About as thick as the base of the wall. Press it flat, middle to edge.
- The inside corner Where floor meets wall. The bit everybody skips.
- Standing water Sponge it out. A floor in a puddle dries last and shrinks last.
Part one
The floor
This one has a delay built into it, which is exactly why people skip it. Nothing bad happens on the wheel. Nothing bad happens that night. You find out two or three weeks later, or you find out when it comes out of a glaze firing with a crack across the bottom that no glaze will ever hide.
It costs about eight seconds. Do it while the pot is a stump and you can still reach the whole floor with a flat hand. Once the walls are up, you are reaching down through a tube, dragging wet slurry over the thing you were trying to help.
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Open to the width you actually want
Pick the floor width now. Widening later drags clay back across a floor you already compressed.
Pick the floor width now. Widening later means dragging clay outward across a floor you have already compressed, which undoes the work and thins the base at the same time.
Watch for: opening a little and telling yourself you will sort it out on the first pull. You will not. -
Measure the floor before you touch it
Needle tool straight down to the bat, pinch, pull out. Aim for about the thickness of the wall base.
Push a needle tool straight down until it hits the bat, pinch it where it leaves the clay, and pull it out. You are aiming for a floor about the same thickness as the base of the wall you are about to pull. For a mug that is somewhere around a quarter of an inch.
Watch for: guessing. Everybody thinks their floor is thinner than it is, right up until they trim through it. -
Slow the wheel down
Compression is pressure, not speed. Take the wheel down to pulling speed.
Compression is pressure, not speed. A fast wheel under a firm finger skips and chatters and can drag the floor off center. Take it down to roughly the speed you would pull at.
Watch for: leaving it at centering speed because you never touched the pedal. -
Press from the middle outward, several times
Finger, damp sponge or the flat of a wooden rib. Dead centre out to the corner. Three or four passes.
Flat pad of a finger, a damp sponge, or the flat edge of a wooden rib. Start in the dead center and travel out to the corner. Lift, come back to the middle, do it again. Three or four passes is plenty.
Watch for: going in circles. You want to travel across the alignment you just created, not follow it around. -
Firm, but not digging
Firm and flat. If you feel it sinking in, you are thinning the floor instead of compressing it.
If you can feel your finger sinking in, you are thinning the floor rather than compressing it, and a floor you dug a divot into is worse off than one you left alone. The feeling you want is pressing a sticker flat, not scooping ice cream.
Watch for: enthusiasm. The people who overdo this are always the ones who just learned why it matters. -
Get right into the corner
Push all the way out until you touch the wall. The corner is the bit everybody quietly skips.
The join between the floor and the wall is the awkward bit, so it is the bit that quietly gets left out. Push your finger or the rib all the way out until it touches the wall, then stop. That corner should be a clean curve, not a puddle with a lip.
Watch for: stopping short because your knuckle is in the way. Turn your hand, do not shorten the pass. -
Sponge the water out, and do it again at the end
Mop the standing water before you pull, and again before it goes to your shelf.
Water pooling in the base soaks into the floor and keeps it wet long after the rest of the pot has firmed up. Mop it before you pull, and mop it again before the pot goes to your shelf. If you like, run a rib across the inside of the finished base one last time.
Watch for: carrying a pot to the shelf with a little lake in the bottom of it. Very common, completely avoidable.
If you throw off the hump, this changes
You cannot compress a floor against a wheel head that is not there. Throwing off the hump means the base of your pot is sitting on more clay, so pressure just pushes into the lump. The workarounds are the same ones that help everybody else: keep the floor close to wall thickness, keep standing water out of it, and dry the piece slowly and evenly with the base covered.
Now go watch somebody do it
One long and thorough, one that takes two minutes, and one about the hardest version of the job. They open the player only when you press play.
Nothing loads from YouTube until you press play.
The honest part
Potters do not actually agree on why this works
We could have left this out and you would never have known. But you are going to run into it eventually, probably from somebody at a wedging table who is very sure, and we would rather you heard it here first.
Particle alignment
Opening the pot drags those flat platelets outward from the center until they all point the same way, like the spokes of a wheel. Shrinkage then pulls along that alignment and the floor splits down a line it was already lined up to split along. Compression scrambles and closes it back up.
Shrinkage stress
Others argue the alignment story is not the real culprit, and that cracks come from parts of the same pot drying and shrinking at different rates. A thick floor under thin walls is the classic setup. On this view compression helps mostly because it also evens the floor out and drives water off it.
Which is a much less interesting argument than it sounds
Because both camps tell you to do the exact same things. Compress the floor. Keep it close to wall thickness. Sponge the water out. Dry it evenly. Nobody in this argument is telling you to skip a step.
So we teach compression as a habit and we do not pretend the science is fully settled. If you do all four of those things and a pot still cracks, that is genuinely useful information, and it usually points at drying rather than at your hands.
Part two
The rim
The floor punishes you later. The rim punishes you immediately, which at least is honest of it. A rim you never compressed tears halfway up your third pull, and then the tear takes the wall with it, and then you are sitting there holding a wet ring wondering what happened.
Every pull stretches the rim thinner. Every single one. So compressing once at the end does not undo four rounds of stretching, it just tidies up the survivor. This is a between-pulls habit, not a finishing step.
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Ease off the pressure before you get there
Let the squeeze fade out over the last inch so the rim ends up heavier than the wall below it.
Compression starts during the pull. Over the last inch or two, let the squeeze fade out to almost nothing so the rim ends up a touch heavier than the wall beneath it. A rim thinner than its own wall is a flag waiting for wind.
Watch for: full pressure all the way to the top, then wondering why the lip is floppy. -
Compress after every pull, not once at the end
Finish the pull, come off the wall, compress, then start the next pull. Three pulls, three compressions.
Finish the pull, come off the wall, press the rim, then start the next pull. Three pulls means three compressions. It adds maybe four seconds a pot and it is the difference between a rim that behaves and a rim that surprises you.
Watch for: treating it as the last thing you do before wiring off. -
Two fingers and a thumb, slow wheel
Finger and thumb on the inside and outside, one finger resting on top, wheel slow. Light contact.
Index finger and thumb of one hand lightly on the inside and outside of the lip. One finger of the other hand resting on top. Let the wheel turn a couple of times underneath. You are steering the clay back into itself, not squeezing it.
Watch for: pressing hard enough to flatten the lip into a little shelf. Light contact, more rotations. -
Or use a chamois, which is more forgiving
Or wet a chamois, wring it out hard, fold it over the lip and let the wheel turn.
Wet it, wring it out, fold it over the rim so it wraps the inside, the top and the outside at once, and let the wheel turn slowly. It compresses and smooths in one pass and it cannot leave a fingerprint. A folded strip of plastic bag does the same job.
Watch for: a soaking chamois. You are adding water to the thinnest part of the pot, so wring it out properly. -
Level it first if it is wonky, then compress the new edge
Uneven? Needle tool it level, then compress the fresh edge immediately. A cut edge has never been compressed.
A needle tool held steady at the height you want, pushed through while the wheel turns, will take the uneven ring straight off. The edge it leaves behind is a fresh cut and has never been compressed in its life, so do that next, immediately.
Watch for: cutting a beautiful level rim and then walking away from it. That is a crack with a schedule. -
Round it off, and cover it overnight
Round it off, no knife edges, and drape plastic loosely over the rim for the first day of drying.
Do not leave a knife edge. Sharp rims tear on the wheel, chip in the greenware stage and cut lips after firing. Then, on the shelf, drape the rim loosely with plastic for the first day so it does not race ahead of the rest of the pot.
Watch for: a rim that dries first, shrinks first, and cracks while attached to a wall that has not shrunk yet.
Nobody has made the rim video that should exist
Watch it once
We went looking for a proper, dedicated, well-shot explainer on compressing a rim, from somebody who teaches for a living. It is not out there. Rim work only ever shows up buried inside twenty-minute throwing videos, which is a decent chunk of why everybody skips it. So here is the best short one, and here is the long one where you can watch it happen in real workflow.
Nothing loads from YouTube until you press play.
Keep this bit open
The whole page, on one screen
No explanations, no reasons, nothing to read twice. This is the version for when you are already sitting at a wheel with clay to the elbow. Leave it up on your phone next to the splash pan.
Floor · once, right after you open
- Open it to the width you want. Final answer.
- Needle tool straight down. Floor about as thick as the wall base.
- Slow the wheel to pulling speed.
- Finger, sponge or flat rib. Middle to edge. Three or four passes.
- Firm and flat. If it is sinking in, back off.
- Push all the way into the corner every pass.
- Sponge out standing water. Do it again before it goes on the shelf.
You will not get another good shot at this once the walls are up.
Rim · after every single pull
- Ease off pressure over the last inch of the pull.
- Come off the wall. Compress. Then start the next pull.
- Finger and thumb on the sides, one finger on top, slow wheel.
- Or a wrung-out chamois folded over the lip.
- Uneven? Needle tool it level, then compress the new edge straight away.
- Round it off. No knife edges.
- Loose plastic over the rim for the first day of drying.
Three pulls means three compressions, not one at the end.
What to press with
Six things, and you already own most of them
None of these are better than the others in general. They are better at different moments, and most potters end up using three or four of them on the same pot without thinking about it.
Free, always with you, and the only tool that tells you what the clay is doing while you use it. Start here. Everything else is a refinement of this.
Spreads the pressure over a wider area than a fingertip, so it is more forgiving if your hand is unsteady. It also mops as it goes, which is half the job.
Rigid, so it cannot flex away from the clay the way a tired finger does. Best pass for flattening a floor that has gone slightly domed or dished.
Bends into the corner where the floor meets the wall, which is exactly where fingers give up. It also skims slurry off, and slurry left sitting is water left sitting.
Wraps the inside, the top and the outside of the lip in one pass and cannot leave a fingerprint. Wring it out hard first. A soaked chamois is doing the opposite of helping.
The free version of a chamois, and plenty of production potters prefer it. Fold it a few times, drape it over the rim, let the wheel do the work.
You do not have to buy all of this
Studio tools are included from Yellow Level upward, and there are hundreds of them. Green Level Members bring their own starter tools, and a sponge, a wooden rib and a needle tool will cover everything on this page.
When it goes wrong
What happened to yours?
Six failures that trace back to one of these two moves. Tap the one that matches and we will tell you which step it was.
An S-shaped crack in the bottom
Almost always the floor was never compressed after opening, or it was compressed once, gently, in circles. Press from the middle outward, firmly, three or four separate passes, immediately after you open. This crack often does not appear until the pot is drying or even until after a firing, which is why it feels like it came out of nowhere.
Also check a floor much thicker than the walls, and water left standing in the base. Both make the bottom the last part of the pot to dry, and last to dry is last to shrink.
The rim cracked while drying
Almost always the rim dried far ahead of everything under it. It is the thinnest part and it is the most exposed, so it shrinks first while it is still attached to a wall that has not shrunk yet. Drape plastic loosely over the rim for the first day.
Also check a rim that was never compressed, or one that got a small tear during a pull and then had the tear smoothed over rather than cut out. A smoothed-over tear is still a tear, and drying finds it.
The rim tore during a pull
Almost always a rim that got thinner than the wall below it. That happens when you hold full squeeze all the way to the top of every pull. Ease off over the last inch so the rim stays a little heavier, and compress it before you start the next pull.
Also check a rim that had gone dry while you were fussing with the base. Dry clay under a moving hand grabs instead of sliding, and a grab at the rim is a tear.
A ring cracked around the inside base
Almost always the corner where the floor meets the wall never got compressed, because it is awkward to reach and everybody quietly stops an inch short of it. That join is a sharp change in thickness, and sharp changes in thickness crack.
Also check water pooling in exactly that corner while you threw. Run a flexible metal rib around it, which compresses and mops in the same pass.
I trimmed straight through the bottom
Almost always you never measured the floor, so you were trimming blind. Push a needle tool down to the bat and pinch it before you compress, every time, until you stop needing to. It takes three seconds and it is the only way to actually know.
Also check compressing so enthusiastically that you thinned the floor while you were trying to strengthen it. Compression is firm pressure across a surface, not digging a hollow.
The rim dried wavy and out of round
Almost always the rim was left soft and thin, so it had nothing to hold its shape with. A compressed rim is denser and stiffer than an uncompressed one and it holds a circle much better while it dries.
Also check how you carried it. A freshly thrown pot remembers everything, and picking one up by the rim on the way to the shelf is the single most common cause of an oval mug in this building. Carry it by the bat.
The short version
Fifteen seconds, spent at the right two moments
Almost nothing else in throwing has this ratio. Centering takes months. Pulling takes months. Compressing takes an afternoon to learn and then it is just a thing you do, forever, without thinking about it.
The only hard part is that you will never see the payoff. Nobody hands you a pot that did not crack and says well done. You just quietly stop losing work, and after a while you forget you ever did.
Read it once. Watch it once. Then do it eight hundred times without thinking about it.