Absorption
How much water a fired clay body soaks up, given as a percentage. Low absorption is what makes a pot waterproof.
Pottery words, defined
The Plain English Pottery Dictionary
254 terms from clay to kiln, written the way somebody would actually explain them to you at a table. No circular definitions, no words that only make sense if you already knew the answer.
254terms defined
8areas of the craft
64linked to a full guide
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The wheel
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Decorating
The wheel
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The wheel
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The wheel
Decorating
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Decorating
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Clay and clay bodies
Clay and clay bodies
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Tools and equipment
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Kilns and firing
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Clay and clay bodies
Kilns and firing
Kilns and firing
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Kilns and firing
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Clay and clay bodies
Kilns and firing
Kilns and firing
Kilns and firing
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Hand building
Clay and clay bodies
Tools and equipment
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Decorating
Glaze and surface
Glaze and surface
Clay and clay bodies
Clay and clay bodies
Tools and equipment
Glaze and surface
Studio and trade words
Kilns and firing
Hand building
Tools and equipment
Tools and equipment
Clay and clay bodies
Clay and clay bodies
Hand building
Decorating
Tools and equipment
Clay and clay bodies
Kilns and firing
Kilns and firing
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Hand building
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Clay and clay bodies
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Hand building
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Decorating
Clay and clay bodies
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Studio and trade words
Tools and equipment
The wheel
The wheel
The wheel
The wheel
Decorating
Clay and clay bodies
Glaze and surface
The wheel
The wheel
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Decorating
Studio and trade words
Glaze and surface
Clay and clay bodies
Studio and trade words
Clay and clay bodies
Studio and trade words
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Decorating
Clay and clay bodies
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Look it up
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A
Alumina
The stiffener in a glaze. It stops the melt running off the pot and gives a matte glaze its surface.
Anagama
A long single chamber wood kiln built into a slope. Fired for days.
Armature
A temporary internal support, often crumpled newspaper, holding a form up until the clay can hold itself.
Ash glaze
A glaze using wood or plant ash as a flux. Unpredictable in the way people who love it want it to be.
Atmospheric firing
Any firing where what is in the air does the decorating: salt, soda, wood ash, smoke.
Read the full guideAttachment
Any piece joined onto another, such as a handle, a spout, a knob or a foot. Every attachment is a future crack unless it is joined properly.
Read the full guideB
Bag wall
A low interior wall in a fuel kiln that steers the flame away from the work nearest the burners.
Ball clay
A very fine, very plastic secondary clay. Almost never used on its own, and added to a clay body to make it more workable.
Ball mill
A rotating jar full of grinding media, used to mill glaze materials finer than they arrive.
Banding wheel
A hand turned turntable used for decorating, joining and building. Not powered.
Barium
A flux that produces distinctive matte surfaces and is handled carefully because of its toxicity in raw form.
Bat
A flat disc that clips or sticks to the wheel head so a pot can be lifted off without touching it.
Bat pins
The two pins on the wheel head that a bat drops onto.
Bat wash
See kiln wash.
Batch
One mixed quantity of a glaze recipe. Two batches of the same recipe can still fire differently.
Bentonite
An extremely fine clay added in tiny amounts to make a body or a glaze more plastic and keep a glaze from settling.
Biscuit
The British word for bisque. Same firing, same meaning.
Bisque
Clay that has been fired once, without glaze. It is hard enough to handle and still porous enough to drink glaze. The Clay Hole bisques to cone 05.
Bisque firing
The first firing, which drives out the last chemical water and turns clay permanently into ceramic. The Clay Hole fires bisque to cone 05.
Read the full guideBisqueware
A piece that has been through the bisque firing and is waiting to be glazed.
Blistering
Raised bubbles or burst craters in a fired glaze, from gas trapped under a surface that had already sealed.
Read the full guideBloating
Bubbles swelling out of the clay itself in the glaze firing, from overfiring or from carbon that never burned out in the bisque.
Blunger
A machine that mixes clay and water into slip.
Body
Short for clay body. A specific recipe of clays and other materials, blended to fire to a particular cone with particular properties.
Bone dry
Clay that has given up all the water it can at room temperature. Pale, even in color, and room temperature against your cheek. The only state that is safe to fire.
Read the full guideBreaking
What a glaze does where it runs thin over an edge or a texture and shows a different color. The whole point of most textured work.
Bung
A plug for a kiln spyhole.
Burnishing
Polishing leather hard or bone dry clay with a smooth stone or the back of a spoon until it shines, with no glaze involved.
C
Calcine
To fire a raw material before using it, driving off water and gas so it behaves predictably in a glaze.
Candling
Holding a kiln at a low temperature for hours at the start of a firing to drive off any remaining water safely.
Carbon coring
A gray or black band in the middle of a fired wall, left when organic matter in the clay did not burn out during the bisque.
Celadon
A pale green to blue transparent glaze, traditionally colored with a small amount of iron.
Centering
Pushing the clay until it runs true, so every point on it stays the same distance from the middle as the wheel turns. Everything else on the wheel depends on this.
Read the full guideChamois
A soft leather scrap used to compress and smooth a rim.
Chattering
A regular ripple of skipped cuts left by a trimming tool that is bouncing. Sometimes a mistake, sometimes a surface people chase on purpose.
Read the full guideChuck
A form that holds an awkward pot upside down for trimming, usually a thrown cylinder or a foam collar.
Chun
A thick, pale blue, opalescent glaze. The blue is an optical effect rather than a colorant.
Clay body
The blend a potter actually works with. Stoneware, porcelain and earthenware are families of clay bodies, not single materials.
Clay trap
A tank under a studio sink that catches clay before it reaches the drain. Emptying it is a rite of passage.
Cobalt
The strongest blue colorant in ceramics. A very small amount goes a very long way.
Coil building
Building walls from rolled ropes of clay, joined and blended. The oldest way to make a pot and still one of the best for large work.
Collaring
Squeezing a pot inward with both hands to narrow it. How a cylinder becomes a bottle neck.
Collaring in
See collaring.
Colored clay
Clay stained through its whole mass with mason stains or oxides, rather than colored on the surface. Colored scrap never goes in the communal reclaim.
Read the full guideCombing
Dragging a toothed tool through wet slip to leave a pattern of parallel lines.
Compression
Pressing clay particles back together, most importantly across the floor and around the rim. Most cracks are a compression problem wearing a different costume.
Read the full guideCone
A small shaped pillar that bends at a known amount of heatwork. It measures temperature and time together, which is what actually matters to clay.
Read the full guideCone 05
The bisque firing at The Clay Hole. The leading zero means it is a low fire cone, around 1,888 degrees F at a standard climb.
Read the full guideCone 5½
The glaze firing at The Clay Hole. Cone 5 with a twelve minute hold, which lands between cone 5 and cone 6.
Read the full guideCone pack
Three cones set together, one below, one at and one above the target, so you can see whether a firing landed short, right or long.
Coning
Pushing the clay up into a cone and back down again during centering. It aligns the clay particles and pushes air out.
Cooling crack
See dunting.
Read the full guideCopper red
A red produced from copper in a reduction firing. Famously hard to repeat.
Cottle
The wall or collar built around a model to hold plaster while a plaster mold sets.
Crackle
Crazing used on purpose, often with ink or stain rubbed into the cracks to show them off. Not food safe.
Cranked
Said of a kiln lid propped open slightly during the early part of a bisque to let moisture out.
Crawling
Glaze that pulls itself into islands and leaves bare clay between them, usually from dust, oil or a coat applied too thick.
Read the full guideCrazing
A web of fine cracks in a fired glaze, caused by the glaze shrinking more than the clay under it. It is a fit problem, and a refire does not fix it.
Read the full guideCrystalline glaze
A glaze grown with visible crystals in it, which takes a specialized firing schedule with long holds.
Read the full guideD
Damper
A sliding plate in a fuel kiln's flue that controls the draft, and with it the atmosphere.
Darting
Cutting a wedge out of a slab and closing the gap to pull a flat sheet into a curve.
Deairing
Pulling air out of clay under vacuum, which is what a deairing pug mill does.
Decal
A printed ceramic transfer fired on over an already glazed surface, usually in the decorating range.
Deflocculant
A material that makes a clay slip pour like cream with much less water in it. Sodium silicate is the common one.
Dipping glaze
Glaze kept in a bucket, thin enough to dip a whole pot into in one motion. It behaves differently from brush on glaze and needs its own training.
Read the full guideDipping tongs
Spring tongs that hold a pot by two points while it is dipped, so fingers never touch the glaze.
Downfire
A controlled slow cooling, programmed rather than left to happen. It changes what a glaze does on the way down.
Drape mold
A form you lay a slab over the outside of. The slab takes the shape of the mold's back.
Dryfoot
To wipe glaze off the bottom of a piece so it does not stick to the shelf. Skipping it is how a shelf gets ruined.
Dunting
A clean crack that happens in the kiln after the glaze has already melted, from cooling too fast. The sharp glaze edges at the break are the tell.
Read the full guideE
Earthenware
Clay that matures at low fire and stays porous. Terracotta is the one most people picture.
Element
The coiled wire in an electric kiln that glows and produces the heat. They wear out and need replacing.
Engobe
A slip with added flux, so it sits somewhere between a slip and a glaze and fits a wider range of clay.
Ergonomics
How a workspace is set up around a body. Wheel height, stool height and posture decide how long you can work without pain.
Eutectic
The mix of materials that melts at the lowest temperature. Glaze chemistry is largely the hunt for a useful one.
Extruder
A tool that pushes clay through a shaped die to make handles, coils and hollow tubes of a consistent profile.
Read the full guideF
Faceting
Cutting flat planes into a round pot with a wire or a blade.
Feldspar
The most common flux in mid and high fire glazes, and a major ingredient in many clay bodies.
Fettling
Cleaning up seams and rough edges on a leather hard or greenware piece.
Fettling knife
A long thin blade for trimming seams and cutting leather hard clay.
Fire down
See downfire.
Fireclay
A coarse, heat resistant clay. Adds tooth and strength to stoneware bodies and to anything large.
Firing fee
What the studio charges to fire a piece, calculated from its volume in cubic inches. Bisque firing is free.
Read the full guideFiring schedule
The programmed sequence of ramps, holds and targets a kiln runs. Two kilns reaching the same cone on different schedules give different results.
Flashing
Color left on bare clay by the atmosphere in a kiln rather than by a glaze.
Flocculate
To thicken a glaze or slip so the particles stay suspended instead of settling into a brick at the bottom.
Flux
The material in a glaze that makes the silica melt at a reachable temperature. Without a flux, a glaze is just sand.
Food safe
A fired surface that is stable, does not leach, and has no crazing or shivering. A glaze is only food safe on the clay body and at the cone it was tested on.
Foot
The base a pot stands on. A foot ring is the raised circle left when the middle is trimmed away.
Read the full guideFooted bowl
A bowl raised on a foot rather than sitting flat.
Read the full guideFrit
Glass that has been melted, cooled and ground up so it can go into a glaze safely and melt predictably.
Fritware
A body containing a high proportion of frit. Historically used for very white low fire ware.
G
Gallery
The interior ledge a lid sits on.
Read the full guideGas kiln
A fuel burning kiln, which can be fired in reduction. Electric kilns cannot, without ruining the elements.
Glaze defect
Any unintended result in a fired glaze. Naming it correctly is most of fixing it.
Read the full guideGlaze firing
The second firing, which melts the glaze into glass and matures the clay body. The Clay Hole fires glaze to cone 5½.
Glaze fit
How well a glaze and a clay body shrink together as they cool. Bad fit crazes or shivers. It is a pairing problem, never a single ingredient problem.
Glaze tongs
See dipping tongs.
Glaze wall
The shelves holding the studio's glazes. There are 650+ brush on glazes and 150+ underglazes.
Read the full guideGlossy
A glaze that fires to a shiny, reflective surface. The right choice for a rim you are going to drink from.
Green
Unfired. Applies to anything from the moment it is made until it comes out of the bisque.
Green strength
How much handling unfired clay will take before it breaks. Grog and fiber both raise it.
Greenware
Unfired pottery, usually meaning it is dry and waiting to be bisqued. Fragile to the point of being annoying.
Greenware shelf
Where unfired work waits to dry and be collected for the bisque.
Grog
Fired clay ground up and added back into a clay body. It cuts shrinkage, adds strength while you work, and gives the clay a gritty tooth.
H
Handbuilding
Making pottery without a wheel: pinching, coils, slabs and carving.
Hard brick
Dense refractory brick used where a kiln takes wear. It holds heat, which also means it takes longer to cool.
Heatwork
The total effect of temperature and time on clay. The reason a cone is more useful than a thermometer.
Read the full guideHold
Time spent parked at one temperature rather than climbing. A twelve minute hold at cone 5 is what makes cone 5½.
Hollowing
Cutting the inside out of a solid form so it can dry and fire safely. Anything thicker than about an inch wants hollowing.
Hump mold
A form you lay a slab over, the opposite of a slump mold. The slab takes the shape of the mold's outside.
I
Inlay
Filling carved lines with a contrasting clay or slip, then scraping back so only the lines show.
Iron oxide
The most used colorant in ceramics. Gives everything from pale celadon green to near black depending on amount and atmosphere.
J
Jigger
A machine that forms a plate or bowl by pressing a template against clay on a rotating mold. Industrial rather than studio.
K
Kaolin
The purest and whitest clay, and the backbone of porcelain. On its own it is not very plastic.
Kiln cookie
A small disc of clay placed under a piece to catch a running glaze and save the shelf.
Read the full guideKiln furniture
The shelves, posts and stilts that hold work inside a kiln.
Kiln post
A refractory column that holds a shelf at the height you need.
Kiln shelf
The refractory slab pots sit on. Expensive, heavy, and ruined by one runny glaze.
Kiln sitter
A mechanical shutoff that drops when a small cone under a rod softens. Older kilns use these instead of a digital controller.
Kiln wash
A protective coating painted onto a shelf so a glaze drip can be chipped off instead of becoming permanent.
Kurinuki
Carving a vessel out of a solid block of clay rather than building it up.
L
Lawn
To sieve a glaze through a fine mesh. A glaze that has not been lawned goes on lumpy.
Leather hard
Clay that has stiffened enough to hold its shape and handle its own weight, and is still damp enough to carve, trim and join. Most of the work after throwing happens here.
Level
A Clay Hole membership tier. Green Level, Yellow Level, Purple Level and Black Level, lowest to highest.
Read the full guideLid seat
See gallery.
Read the full guideLoop tool
A wire loop on a handle, used for trimming and carving.
Luster
A metallic overglaze fired in the decorating range. The studio does not stock lusters, so members bring their own.
M
Majolica
Color painted onto an unfired white glaze, so the decoration fuses into the surface in one firing.
Mason stain
A manufactured ceramic color, fired stable and ground to a powder. Used in clay, in slip and in glaze.
Read the full guideMatte
A glaze that fires to a soft, non reflective surface. Can be lovely and can also be unpleasant on a rim.
Maturity
The point where a clay body has been fired as hot as it should be: dense, strong and not yet deforming.
Mishima
A slip inlay technique. Carve the line, fill it, scrape it back.
Read the full guideMoon jar
A large round jar thrown in two halves and joined at the middle.
Read the full guideMuffle
A chamber that keeps the flame off the work in a fuel kiln.
N
Needle tool
A pin on a handle. Cuts rims level, pops bubbles, and measures floor thickness.
Neriage
Throwing or building with colored clays layered together so the pattern runs through the wall.
Read the full guideO
Off the hump
Throwing several small pots one after another from the top of one large centered lump.
Once fired
Glazed onto raw clay and fired a single time, skipping the bisque. It works and it is less forgiving.
Opaque
A glaze you cannot see the clay through.
Open studio
Studio time with no class running. An Open Studio Manager is there to run the room, not to teach.
Opening
Pressing down into the centered clay to make the floor and set its depth. Go too deep and the pot has no bottom.
Overglaze
Anything applied on top of an already fired glaze and fired again at a lower temperature. The studio does not stock overglazes.
Read the full guideOxidation
A firing with plenty of oxygen in the kiln. Every electric kiln fires this way by default.
Oxide
A metal compound used to color clay, slip or glaze.
Read the full guideOxide wash
A thin mix of metal oxide and water brushed on and wiped back, so it stays in the texture and off the high points.
P
Paddle
A flat piece of wood used to beat a form into shape or to compress a wall.
Peep hole
See spyhole.
Pinch pot
A pot made by pressing a thumb into a ball of clay and pinching the wall out. Where most people start.
Pinholing
Small sharp holes left when gas escaped through a glaze that had already started to set.
Read the full guidePit firing
Firing pottery in a pit packed with combustibles. No glaze, all atmosphere.
Read the full guidePlaster bat
A slab of plaster that pulls water out of clay. Used for reclaim and for stiffening soft clay quickly.
Plasticity
How far clay will bend before it tears. High plasticity throws beautifully and shrinks more.
Porcelain
A white, dense, often translucent clay body. Unforgiving on the wheel and worth it.
Porosity
How much open space is left in a fired body. High porosity drinks glaze and holds water.
Potter's wheel
The powered turntable a thrown pot is made on. The Clay Hole runs 29 of them.
Press mold
A form clay is pressed into rather than poured into.
Primary clay
Clay still sitting where it formed. Pure, white and not very plastic. Kaolin is the example.
Profile
The outline of a form seen from the side. Most of what makes a pot look right or wrong.
Pug mill
A machine that mixes and compresses reclaimed clay into usable blocks, doing most of the wedging for you.
Pulling
Drawing the wall up and thinner between the fingers of both hands. Height comes from the first inch of the pull.
Pulling a handle
Shaping a handle by repeatedly drawing a wet hand down a lug of clay until it thins and curves.
Read the full guidePyrometer
A thermometer for a kiln. It reports temperature and knows nothing about time, which is why cones still matter.
Q
Quartz inversion
A point around 1,063 degrees F where silica in the clay suddenly changes volume. Rush a kiln through it and pieces crack.
R
Raku
Pulling work glowing hot from the kiln and putting it straight into combustibles. Fast, dramatic, and not food safe.
Read the full guideRamp
A programmed stretch of a firing, written as a speed and a target. Most schedules are three or four ramps in a row.
Rasp
A coarse file for shaping leather hard or bone dry clay. Makes a lot of dust, so it is a wet tool.
Raw glazing
Glazing unfired clay. See once fired.
Reclaim
Scrap clay slaked down in water and dried back to working consistency. Nothing is wasted in a pottery studio except your time.
Read the full guideReduction
A firing where oxygen is deliberately starved, so the flame pulls it out of the materials instead. It changes glaze colors completely and needs a fuel kiln.
Refire
Putting a glazed piece back through the glaze firing. It fixes some faults and makes others worse.
Read the full guideRefractory
Able to take heat without melting or deforming. Shelves, posts and kiln brick are all refractory.
Refractory brick
See hard brick and soft brick.
Rib
A flat shaped piece of wood, metal or rubber used to shape, compress and smooth. A metal rib cuts, a rubber rib smooths.
Read the full guideRutile
A titanium bearing material that breaks a glaze into streaks and mottles. Responsible for a great many studio favorites.
S
S crack
A curved crack across the floor of a thrown pot, left by a floor that was never compressed. It goes all the way through, so the piece is finished.
Read the full guideSaggar
A sealed container a piece is fired inside, packed with materials that mark the surface.
Read the full guideSagger
See saggar.
Read the full guideSalt firing
Throwing salt into a hot kiln so it vaporizes and forms a glaze on everything inside, including the kiln.
Read the full guideSatin
Between glossy and matte. A soft sheen.
Score and slip
Scratching both surfaces and wetting them with slip before joining. Two pieces of clay pressed together without it are stacked, not joined.
Read the full guideSecondary clay
Clay that has been moved from where it formed by water or wind, picking up impurities and plasticity along the way.
Serrated rib
A rib with teeth, used to score a surface or to pull texture through a wall.
Settling
What a glaze does in the bucket when it is left alone. Every dipping glaze needs stirring before use.
Sgraffito
Scratching through a layer of slip or underglaze to reveal the clay color underneath.
Shino
A family of thick, crusty, carbon trapping glazes, traditionally Japanese and traditionally unpredictable.
Shivering
Sharp slivers of glaze flaking off edges, because the glaze shrank less than the clay. The dangerous one, and never safe for food.
Read the full guideShort
Clay with too little plasticity. It cracks as soon as you bend it and fights every pull.
Shrinkage
How much smaller a piece gets between wet clay and fired pot. Most stoneware loses somewhere around twelve percent, and it happens in two stages, drying and firing.
Read the full guideSieve
A mesh screen for straining lumps out of glaze or slip.
Silica
The glass former. The thing in a glaze that actually becomes glass.
Silica dust
Fine airborne clay dust, which is a genuine long term lung hazard. It is why studios wet mop instead of sweeping and why nothing dry gets sanded indoors.
Single fire
See once fired.
Slab
A flat sheet of clay, rolled by hand or run through a slab roller.
Slab molds
Forms that shape a rolled slab into a finished object. The Clay Hole keeps 248 of them, and they are not slip cast molds. The studio does not slip cast.
Read the full guideSlab roller
A machine that rolls clay into an even slab at a set thickness, much faster and flatter than a rolling pin.
Read the full guideSlake
To let dry clay sit in water until it falls apart on its own. The first step of reclaiming.
Slip
Clay mixed with water to a creamy consistency. Used to join pieces, to decorate, and to cast.
Read the full guideSlip casting
Pouring liquid clay into a plaster mold, letting a skin form, and pouring the rest out. The studio does not offer it and never will.
Slip trailing
Piping slip through a fine nozzle to draw raised lines.
Slump mold
A dish shaped form you lay a slab into. The slab slumps down and takes the inside shape.
Slurry
The thick sloppy mixture of clay and water that builds up on the wheel. Useful for joining, and the reason the wash pit exists.
Soak
Another word for a hold.
Soft brick
Lightweight insulating brick. Cuts with a saw, holds very little heat, and damages easily.
Soft slab
Building with slabs while they are still floppy, so the clay curls and settles into its own shapes.
Sponge on a stick
A sponge on a thin dowel, for getting water out of the bottom of a tall narrow pot.
Spout
The pouring part of a teapot or pitcher. The hardest attachment to get right.
Read the full guideSprig
A small shape formed in a little mold and applied to the surface of a piece.
Read the full guideSpyhole
A small plugged hole in a kiln wall for looking at cones during a firing.
Stiff glaze
A glaze that does not move much at temperature. Safer near a foot and less interesting over texture.
Stilts
Small pointed supports that hold low fire glazed ware off the shelf. Not used at mid fire, where the pot is soft enough to sag on them.
Stoneware
The workhorse clay family. Fires dense and waterproof at mid to high fire, and takes daily use.
Stoneware clay
See stoneware.
T
Tap centering
Centering a leather hard pot for trimming by tapping it into true while the wheel spins, rather than measuring it.
Template
A cut profile used to check or cut a shape, so several pieces come out matching.
Tenmoku
A dark iron saturated glaze that breaks rust brown where it runs thin over an edge.
Terra sigillata
An ultra fine slip, polished to a soft sheen. Ancient, and still the best way to get a satin surface with no glaze at all.
Terracotta
A red earthenware body. Warm, porous and low fire.
Test tile
A sample piece fired with a known number of coats on a known clay body, so you can see what a glaze really does. A tile is a promise about a thickness and nothing else.
Read the full guideTest tile pot
The shaped pot every Clay Hole glaze tile is fired on, which shows one glaze over four different surfaces at once.
Read the full guideThermocouple
The probe that tells a kiln controller how hot it is. It drifts as it ages, which is why a cone is the honest check.
Throwing
Making a pot on a spinning wheel. The name comes from an old word meaning to twist or turn, not from throwing anything.
Throwing off the hump
See off the hump.
Read the full guideThrowing rings
The spiral ridges left by your fingers on a thrown wall. A signature, not a flaw.
Throwing water
The water you dip into while throwing. Every extra dip weakens the wall.
Tile
A flat fired slab. Harder to make well than it sounds, because flat things warp.
Tooth
The grittiness a clay has from grog or sand. More tooth means a wall stands up better and your fingertips wear out faster.
Transparent
A glaze you can see the clay or the underglaze through.
Trimming
Cutting away leather hard clay on the wheel to refine the shape and cut a foot.
Read the full guideTurning
The British word for trimming.
Read the full guideU
Underfired
Fired short of the cone it needed. Clay stays porous and glaze stays dry and rough.
Underglaze
Color applied before the glaze, usually on bisque or leather hard clay. It holds its line instead of moving, which is why it is used for drawing.
Read the full guideUp-charge glaze
A premium glaze at The Clay Hole that costs extra per piece, paid the day it is glazed.
Read the full guideV
Viscosity
How stiff a glaze is when it is molten. Low viscosity runs onto the shelf.
Vitrify
To fire clay hot enough that it fuses into a dense, glassy, waterproof solid. A pot that does not vitrify will always seep.
Volumetric pricing
Charging for a firing by the space a piece takes up rather than by the piece. The Clay Hole charges by the cubic inch.
Read the full guideW
Warping
A piece going out of shape during drying or firing. Flat and wide forms are the worst affected.
Read the full guideWash pit
The sink area with a clay trap, where everything gets rinsed. Clay never goes down an ordinary drain.
Water smoking
The early stage of a bisque where the last physical water leaves the clay. Rushing it is how pieces explode.
Wax emulsion
See wax resist.
Wax resist
Wax brushed where glaze should not stick, most often the foot. It burns away in the firing.
Wedging
Kneading clay to drive out air pockets and make the moisture even throughout. The step people skip and then regret.
Read the full guideWedging table
A plaster or canvas topped bench for wedging. Plaster also pulls water out of clay that is too soft.
Wet mopping
The only safe way to clean a pottery floor. Sweeping puts silica dust back into the air.
Wheel head
The metal disc that spins. Bats attach to it.
Whiting
Calcium carbonate. One of the most common fluxes in mid and high fire glazes.
Wild clay
Clay dug from the ground rather than bought. It takes processing, testing and patience, and no two sources behave the same.
Wire cut
The marks left on the bottom of a pot cut off the wheel with a wire. Often left visible on purpose.
Wire tool
A length of wire with two toggles, used to cut clay off the wheel and to slice a block for wedging.
Witness cone
A cone placed where you can see it through the spyhole, or found on the shelf afterward, to confirm what the firing actually did.
Wooden knife
A blunt wooden blade for shaping and cleaning up without cutting into the clay.
Z
Zinc
A strong flux that also affects color, sometimes unhelpfully. Chrome greens in particular dislike it.
Zirconium
The usual opacifier. It is what makes a white glaze white.
Easy to mix up
Pairs that sound the same and are not
cone 05 and cone 5
About 300 degrees F apart. Cones with a leading zero get cooler as the number climbs. Writing one when you meant the other is the most expensive typo in ceramics.
Slip and slurry
Slip is mixed on purpose to a known consistency, for joining and decorating. Slurry is what collects on the wheel while you throw. They are both clay and water, and only one of them is a material.
Crazing and shivering
Both are glaze fit failures, in opposite directions. Crazing is the glaze cracking under tension. Shivering is the glaze popping off under compression, and it leaves edges sharp enough to matter.
Slab molds and slip casting molds
Slab molds shape a rolled sheet of clay that you lay over or into them. Slip casting molds are plaster forms you pour liquid clay into. The Clay Hole has 248 slab molds and does not slip cast.
Underglaze and overglaze
Underglaze goes on before the glaze and holds its line. Overglaze goes on top of an already fired glaze and fires much cooler. The studio stocks underglaze and does not stock overglaze.
Bisque and greenware
Greenware has never been fired and will dissolve in water. Bisque has been through the first firing and is permanently ceramic, just still porous.
Keep going
Words are the cheap part
Knowing that leather hard means the clay will carve without collapsing is worth something. Knowing what it feels like under a trimming tool is worth more, and no dictionary delivers that part.