Material fundamentals

Reading Clay by Feel

Naming the stages of clay is the easy part. This lesson is about the lump in front of you right now: four checks that take about a minute, what each one is telling you, whether that clay suits what you are about to make, and what to change when it does not.

Wedge it briefly, then press, bend, cut and lift. Those four checks tell you whether the clay is workable, too soft, too stiff, uneven, sticky or short, and every one of those has its own fix.

Six conditions, four checks Three exercises that train your hands Three videos, none of them ours
Four checks, about a minute Six conditions, six fixes Stiff or short, settled
Three potters at one studio table testing clay by hand: a smooth workable ball, a stiff block cracking under a palm, and a wet sticky lump slumping onto the canvas
Jump to a section
Why clay feels the way it does The six conditions Question one: what am I noticing? The press and the lift The whole idea The one minute check Six conditions, six fixes The bend: stiff or short The cut face Exercise one: the four piece set Two more exercises Question two: is it right for what I am making? Question three: what should I change? Questions we get asked Keep going

Why clay feels the way it does, four checks, three exercises, and the fix for each condition.

The whole idea

One window of water, and two problems that are not about water

Clay is flat particles with films of water between them. That water is both the glue that holds the particles together and the lubricant that lets them slide. Every clay has a narrow band of water content where it bends without cracking and holds its shape without slumping. That band is what workable means.

Too little water and the particles grip: the clay resists your thumb and cracks when it bends. Too much and they slide too freely: it sags, spreads and sticks to everything. Two more conditions have nothing to do with how much water there is. Uneven clay has its water in the wrong places, a firm skin around a soft middle. Short clay has little stretch in it at all, so it tears even when it is soft.

Clay also firms up when it sits and loosens when it is worked, so judge it after a short wedge, never straight out of the bag.

The mechanism

Why clay feels the way it does

Seven facts. Every check, exercise and fix further down is one of them put to work.

  1. Clay is flat particles in a film of water. The particles are tiny plates with an electrical attraction for water. That water does two jobs at once: it is the glue holding the plates together and the lubricant that lets them slide past each other. Plasticity, the ability to take a new shape and keep it, comes from that pair of jobs.
  2. Every clay has a working window, and it is narrow. A porcelain that throws well at 21 to 22 percent water can turn short and difficult at 19. Two or three percent of the clay's weight is the whole difference between lovely and hopeless, which is why your hands are a better gauge than your eyes.
  3. Too little water and the plates grip. The clay resists pressure, and when you bend it the outside of the curve runs out of stretch and cracks. That is stiff clay, and adding water moves it back into the window.
  4. Too much water and the plates slide too freely. The clay cannot carry its own weight. It sags, spreads, sticks to hands and tools, and the extra water has to leave again as it dries, which raises the risk of drying cracks. On the wheel very soft clay will not go as tall, as thin or as true, and it leaves more to trim.
  5. Water can be in the wrong places. A bag dries from the outside in, a reclaim slab dries from its surface, and two clays wedged together for too short a time stay in layers. The lump feels fine in your hand while one part of it is firmer than another. That is uneven clay.
  6. Some clays have less stretch to begin with. Plasticity depends mostly on how fine the particles are and which particles they are. A body with a lot of sand, grog or coarser clay and not enough fine plastic clay to bond it tears where it is stretched, even at a good softness. That is short clay. A plastic clay dried below its window behaves short as well, which is why the bend alone cannot tell the two apart.
  7. Each clay needs its own amount of water. The more plastic the body, the more water it takes to reach the same stiffness, so two clays can feel identical at quite different water contents. This is why makers who mix clay for a living often trust the feel coming out of the mixer over a number on a scale.

Judge it after a short wedge

Clay sets up when it sits still and loosens again when it is worked, sometimes dramatically. A block straight out of the bag nearly always feels stiffer than it really is. Wedge it for a minute, then check. The fix you need is decided by the clay you will actually be using, not the clay that came out of the plastic.

What you are sorting

The six conditions

Four of them are about how much water is in the clay. Two are not, and those are the two people misread most.

Workable

A thumb sinks in with steady pressure and the dent keeps a smooth rim. A finger thick coil curves over a finger without a crack. The cut face is one tone, and your hand lifts off with no more than a faint film.

It does what you ask and stays where you put it.

Too soft

A thumb sinks with almost no effort and the clay bulges up around it. A ball set on the table sags and spreads. Coils droop off the finger, and it is usually sticky too.

It centers easily and then refuses to stand up. Walls slump as they thin, and joins smear rather than bond.

Too stiff

Real pressure leaves only a shallow dimple. Coils crack across the outside of the bend, the wire drags through it, and your wrists feel the wedging.

It fights centering, cracks at the edge of a pinch and splits along any curve. Water fixes it, given time.

Unevenly conditioned

It can pass the thumb and the bend and still be wrong inside. The cut face gives it away: a pale, firm band around a darker middle, or streaks of firm and soft clay folded together.

On the wheel it is harder to center and tends to wobble as it rises.

Sticky

It clings to your palm, builds up on the table and leaves paste on your skin. Most often that is water sitting on the surface. Very plastic clays are naturally tacky as well, even at a good softness.

It smears instead of moving cleanly and drags on every tool.

Short

It tears open where you stretch it, even when it is soft. Edges split as you wedge or roll it, it makes a lot of slip on the wheel, and it feels flabby and slow to answer your hands.

It resists centering and splits at a stretched rim or belly. Water makes it softer, not stretchier.

Question one Before you make anything

What am I noticing?

The one minute check

Four checks, in this order, every time you open a bag or pick up a lump of reclaim. About a minute in all.

Is your clay too wet/dry? Ceramics & Sculpture at Flintridge Sacred Heart Six minutes on what clay that is too wet or too dry looks and feels like for hand building, what to do about each, and a reminder to score, slip and seal.
  1. Wedge it briefly. A minute is plenty. You are not preparing the clay yet, you are waking it up so that what you feel next is the clay you will actually be using.
  2. The press. Push the pad of your thumb straight down into the top of the lump, with the same steady pressure each time. Notice three things: how far it goes in, how hard you had to push, and what the clay did around the dent.
  3. The bend. Roll a coil about as thick as your finger, a few inches long, and bend it over one finger. Watch the outside of the curve, because that is the side being stretched.
  4. The cut. Pull a wire through the middle of the lump and look straight at the cut face. Then drag a fingertip across it from the edge to the center and feel whether the firmness changes on the way.
  5. The lift. Press your palm flat on top of the lump, then lift straight up. Notice whether the clay lets go of you, and what is left on your skin.
  1. Wedge it briefly first. Enough to wake it up. A block that felt like a brick in the bag can be pleasant a few minutes later.
  2. Press. Push the pad of your thumb straight down. Workable clay takes a clean dent with steady pressure. Too soft sinks easily and bulges up around your thumb. Too stiff barely dents at all.
  3. Bend. Roll a coil about as thick as your finger and bend it over one finger. Workable clay curves smoothly. Cracks across the outside of the curve mean stiff or short; the bend section further down tells you which.
  4. Cut. Wire the lump in half and look at the face. One tone from edge to edge is even. A pale band around a darker middle, or streaks, is uneven.
  5. Lift. Press your palm flat on top and lift it straight off. Workable clay lets go. Sticky clay pulls up after your hand and leaves paste on your skin.
  6. Match it to the job. Ask one question: will this clay bend as far as my piece needs without cracking, and stand as tall as my piece needs without sagging? Two yeses and you start.

Make your hand the gauge

Use the same thumb, the same coil thickness and the same finger every time. A check is only useful if you are comparing like with like, and with practice your hand reads a lump before you have consciously decided anything.

What to change

Six conditions, six fixes

Workable

Use it now, and keep the rest of the bag closed. Open clay firms up faster than you expect in dry air.

Too soft

Wedge it on a dry, absorbent surface such as canvas or bare wood, or wedge in a firmer piece of the same clay. For a lot of it, wrap it in cloth for a day.

Too stiff

If your thumb still dents it, water in the bag overnight. If it does not, slice it before the water goes in. Or slam wedge it together with a soft piece.

Uneven

Keep wedging until a fresh cut face is one tone from edge to edge. For a big difference, cut, stack and slam first, then finish with your usual wedge.

Sticky

Dry your hands, move to a dry surface and leave the lump uncovered for a few minutes. Use less water at the wheel. If the clay is sticky even when it is not wet, work it a little firmer.

Short

Water will not fix it. Give it gentler curves, thicker walls and less flare, keep water off anything you are stretching, or pick a more plastic clay for the job.

Close up

The press and the lift

The press sorts soft from workable from stiff. The drawing cuts each lump in half so you can see what the thumb is doing to the clay underneath it.

Clay thumb press, labeled section sketch: too soft clay bulges and slumps, workable clay takes a clean dent, too stiff clay barely dents
  1. Clay bulges up around the thumb. Too soft. The clay has nowhere firm to push back from, so it rises around the thumb instead of making room for it.
  2. Lump sags and spreads. Too soft again, and you can see it before you touch anything: a ball set down a minute ago is already lower and wider than it was.
  3. Clean dent, smooth rim. Workable. Steady pressure takes the thumb in, the dent keeps its shape, and the clay around it stays smooth.
  4. Barely dents under hard pressure. Too stiff. You can feel your thumb joint bending back before the clay gives. It is still clay and still fixable; it simply needs water.

The lift is the sticky check. Press the whole palm on, lift straight off, and look at the clay and then at your hand.

Clay hand lift test, labeled sketch: a hand lifts cleanly off workable clay, while sticky clay pulls up in peaks and coats the fingers
  1. Hand lifts away clean. Workable. A faint film on the palm is normal; clay is wet. What matters is that the clay let go of you.
  2. Flat print, shape holds. The print stays where your palm left it and the lump keeps its outline.
  3. Clay pulls up with the hand. Sticky. The surface would rather hold on to your skin than to the rest of the lump, so it follows you up in peaks.
  4. Paste left on the skin. A coat you would have to scrape off, not a film you could wipe. Question three, further down, sorts out whether that is water or the clay itself.
The check that settles the argument

The bend: stiff or short

Stiff and short both crack on a bend, and they need opposite answers. Water fixes one and does nothing for the other. The drawing shows how they look different, and the water test below settles it when you are not sure.

Stiff and short both crack on a bend. Water fixes stiff and does nothing for short, so the test below is worth the two minutes.

Clay coil bend test, labeled sketch: a workable coil curves smoothly, too soft sags, too stiff cracks across the outside, short clay tears open
  1. Smooth curve, no cracks. Workable. The outside of the curve stretched as far as it needed to and stayed whole.
  2. Sags and flattens on the finger. Too soft. No cracks, but no strength either: the coil cannot hold its own round shape.
  3. Even cracks across the outside. Too stiff. A firm, round coil with a tidy row of fine cracks, like a stiff slab bent too far. It resisted the bend before it cracked.
  4. Tears open instead of stretching. Short. The coil was soft enough to bend easily, yet it opened in one or two ragged, crumbly splits. Softness and stretch are not the same thing.

The water test

  1. Take a walnut sized piece of the clay that cracked. Wet your hands and knead the water in until the piece feels clearly softer than it did.
  2. Roll the same coil again and bend it over the same finger.
  3. It bends cleanly now: it was stiff. The whole lump needs water, given time.
  4. It is soft now and still tears: it is short. More water will only make it soft and short. Change how you use it instead: gentler curves, thicker walls, less flare.

Where short clay comes from

Mostly from the recipe. Porcelains and bodies heavy in grog, sand or coarse clay have less fine plastic clay holding them together. Reclaim can come back short too, usually after the same clay has been through the cycle several times. Our reclaim lesson covers what to do about that batch.

Close up

The cut face

Uneven clay passes the press and often the bend, because your thumb only reaches the outside. A wire through the middle shows you the inside. Darker means wetter within one clay, so compare tones on the same face, never between two different clays.

Wire cut clay faces, labeled sketch: even clay is one tone, a dried out lump shows a pale band around a darker middle, streaked clay shows unmixed layers
  1. One tone from edge to edge. Even. A fingertip dragged from the edge to the center meets the same firmness the whole way.
  2. Pale, firm band around the edge. The outside has lost water. Typical of a bag that sat open, a lump left on the table, or reclaim dried on cloth.
  3. Darker, softer middle. The same lump's core, still at its old water content. Corner cracks on a block like this mean the outside shrank while the inside did not; the middle is usually good clay.
  4. Soft and stiff layers unmixed. Two clays, or a soft and a firm piece of one clay, wedged together too briefly. They will throw as two different clays until they are one.
Train your hands

Exercise one: the four piece set

Reading about stiff clay teaches you the word. Holding stiff clay in one hand and workable clay in the other teaches you the feel. This exercise makes the comparisons for you from one bag, and the clay goes back to work afterwards.

  1. Start from one wedged lump and cut it into four pieces, each about the size of an orange. Number them in your head, or scratch a number into each with a needle tool.
  2. Piece one stays as it is. Wrap it in plastic. It is your reference for workable.
  3. Make piece two too soft. Wet your hands and knead water in, a little at a time, until a ball of it sags when you set it down.
  4. Make piece three too stiff. Flatten it into a pancake about half an inch thick and leave it uncovered. Check it every fifteen minutes; in dry air it firms faster than you expect. When your thumb barely dents it, ball it back up.
  5. Make piece four uneven. Pinch off a third of piece two and a third of piece three, press them together and wedge only three or four times.
  6. Run all four checks on all four pieces. Press, bend, cut and lift, one piece after another, so each comparison happens within seconds. Do the press with your eyes closed.
  7. Drag a fingertip across the cut face of piece four. Feel the firm and soft layers change under your finger. That is what a firm patch feels like to a pot on the wheel.
  8. Wedge all four back together until a fresh cut face is one tone. You will feel the soft and stiff blending into one clay as you go, which is the most convincing lesson in wedging there is.

What you will notice

Piece two will also be sticky, because surface water is the most common cause of stickiness. And piece three, rolled thin enough, will start cracking on the bend in a way that looks a lot like short clay. That is the whole reason the water test exists.

Train your hands

Two more exercises

One sharpens your hands. The other shows you the condition the four piece set cannot make: a clay that is short by nature.

Exercise two: the blind sort

  • Make the four piece set, or ask the person next to you to make one.
  • Close your eyes and have them hand you the pieces in any order.
  • Name each one from the press alone, then again from the bend alone.
  • Open your eyes and cut each piece to check yourself against the face.
  • Repeat at your next session with a new set, until you can name all four without looking.

Exercise three: two clays, one coil

  • Take a lump each of two different clay bodies, such as a smooth stoneware and a porcelain.
  • Bring both to the same feel with the press, adding water to the stiffer one if needed.
  • Roll two coils of the same thickness and bend both over the same finger.
  • Roll both thinner and bend them over a pencil. The one that cracks first has less stretch.
  • If you throw, center a small ball of each. Potters find throwing two samples side by side the most practical way to compare how plastic they are.
Question two

Is it right for what I am making?

Workable is not one fixed feel. Each way of making asks for its own balance of softness and stretch, and the same lump can be perfect for one job and wrong for the next.

Bad Clay? Try These 4 Fixes Before You Give Up TORYMAK Sixteen minutes on throwing a bag that is too soft, too short or inconsistent, chaptered through wedging, centering, setting the form, building a strong lip and dealing with lumps.

The question that settles most cases: will this clay bend as far as my piece needs without cracking, and stand as tall as my piece needs without sagging? The table spells that out for the common ways of making.

  1. Much of this is preference. Some potters throw noticeably softer than others and like how fast it moves; some build coils firmer and wait less between rows. The right clay is the one that does what your piece needs at the size you are making it.
  2. The job changes the clay as you go. Throwing water softens a wall the longer you work it, and a slab left uncovered firms while you are busy with something else. Check again when the clay starts behaving differently.
  3. Stiff slab building is a later stage. Boxes and straight sided forms want slabs firmed past this point, toward leather hard. Leather Hard Clay: Soft, Hard and What Each Is For picks up from there.
MakingWhat you wantToo soft shows up asToo stiff or short shows up as
WedgingSoft enough to move without straining your wristsSmears and sticks to the tableAching wrists, and edges that split as you push
ThrowingWorkable and even all the way throughCenters fast, then will not go tall, thin or true, and leaves more to trimFights centering; short clay splits at a stretched rim or belly
PinchingWorkable, on the soft sideWalls slump as they thinCracks open at the rim as you pinch
Coil buildingRolls round and bends over a finger without a crackCoils flatten and sag under the next rowCracks on every curve and joins badly
Soft slabs, wrapped or draped over slab moldsBends over the form with no cracks on the outside of the curveStretches thin and slumps out of shapeCracks along the outside of the bend
Modeling and fine detailA little firmer, so an edge stays crispDetail smears and soft parts droopEdges crumble and small parts crack off
Question three

What should I change?

One fix per condition, in the order you are most likely to need them. Where another lesson owns the full method, this gives you the short version and points you there.

Slam wedging for perfect reclaim clay consistancy every time, Reclaiming Clay pt2, Life as a Potter Call Us Temily Nineteen minutes on bringing reclaimed or new clay that is too hard or too soft to one consistency, showing two different ways to slam wedge.
  1. Too soft: give the water somewhere to go. Wedge on a dry, absorbent surface such as canvas or bare wood, which pulls water out as you work. For more than a lump, spread it out on that surface, turn it now and then, and check it often so it does not overshoot. A whole bag can be wrapped in cloth for a day or two. Wedging in a firmer piece of the same clay is the fastest fix of all.
  2. Too stiff: give water time. If your thumb still dents it, water in the bag overnight is usually enough. If it does not, cut it into slices so the water has a way in. Slam wedging it together with a soft piece fixes both bags at once. Waking Up Stiff Clay has every method and how long each takes.
  3. Uneven: wedge until the face agrees. Keep going until a fresh cut face is one tone and one firmness from edge to edge. Our wedging lessons give different counts for different clays, so let the cut face decide rather than a number. A big difference blends faster if you cut, stack and slam it first.
  4. Sticky: find out where the water is. Wet hands, a damp table, water poured on to soften a block, and condensation inside a bag that warmed and cooled all leave water sitting on the surface. Dry your hands, move to a dry surface, leave the lump uncovered for a few minutes and use less water at the wheel. If it is sticky without being wet, the body is simply a very plastic one: work it a little firmer and keep your hands dry.
  5. Short: change how you use it. Run the water test first. If it is truly short, give it shapes that ask less of it: thicker walls, gentler curves and less flare. Throw it reasonably quickly, keep water and slip off any surface you are stretching, and finish rims by throwing rather than cutting them. For work that needs real stretch, choose a more plastic clay; any instructor can tell you which bag on our shelf suits the piece.
  6. Workable: keep it that way. Wrap anything you are not using this minute. Fold the bag closed, squeeze the air out and put the block's weight on the fold.

Sometimes change the job, not the clay

A lump a touch too soft to throw tall will still make a low bowl or a pinch pot tonight. Matching the piece to the clay you have is a fix too, and often the faster one.

Questions we get asked

The ones that come up at the tables

Is clay from a new bag always ready to use?

Usually close, never guaranteed. Bags lose water through the fold, the seam and any pinhole, warm and cool on the shelf, and sit for different lengths of time. Wedge it briefly and run the four checks on every bag, including the first one.

Why does clay feel stiffer in the bag than after wedging?

Clay sets up when it sits still and loosens when it is moved, sometimes a lot. Working it frees the water between the particles again. That is why a block that seems too hard to use is often fine a few minutes into wedging, and why you check after wedging rather than before.

Why does this bag feel different from my last bag of the same clay?

Every bag has its own history: how long it sat, how well it was closed, whether it froze, warmed or got knocked about. A few percent of water can be the difference between workable and short, so small differences in storage show up in your hands. Check each bag on its own.

Can I tell how wet clay is by its color?

Within one lump of one clay, yes: wetter is darker, which is what makes the cut face work. Between clays, no. Different bodies start at different colors, so compare tones on the same face rather than one bag against another.

How do I tell stiff clay from short clay?

Stiff clay resists the bend and then cracks in a neat row. Short clay bends easily and tears in ragged splits. When you are not sure, knead water into a small piece and bend a new coil. If it bends cleanly it was stiff. If it is soft and still tears, it is short.

My clay went sticky while I was wedging it. Why?

Almost always water on the surface: wet hands, a damp or sealed table, or water added to soften the block that has not soaked in yet. Move to a dry, absorbent surface and dry your hands. If the clay is sticky every time, even dry, it is a very plastic body, and a slightly firmer lump will feel better.

Is softer clay easier on the wheel?

Easier to center, harder to raise. Very soft clay moves with little force and then will not stand as tall, as thin or as true, and it leaves more to trim. Workable clay on the soft side is where most people are happiest, and exactly how soft is personal preference.

How do I know when my reclaim is ready?

The same four checks, with extra attention to two of them. The cut face, because reclaim dried on cloth or a board is nearly always firmer outside than in. And the bend, because reclaim that has been through the cycle several times can come back short. Our reclaim lesson covers both.

One last thing

A minute before every piece

Most fights with clay are lost before they start, with a lump that was never going to do what was asked of it. Press, bend, cut and lift take a minute, and they move the decision to the moment it costs nothing: before the pot, not halfway up its wall.

Do the four piece set once and the words on this page turn into something your hands know. After that the checks get faster until they disappear into the way you pick up clay. Come to the studio, open a bag and make something with clay you have read first.

Wedge briefly, then press, bend, cut and lift. Water fixes soft and stiff, wedging fixes uneven, a dry surface fixes most stickiness, and short clay asks for gentler shapes rather than more water.

The Comprehensive Version at the top of the page has the mechanism, a close look at each check, three exercises that train your hands, and a table matching the clay to the job.