Alternative Firing
Nothing you put on a naked raku pot stays on it.
Slip, glaze, all of it: sacrificial. You coat the pot, you fire it, you smoke it, and then you take the whole shell off and throw it away. What is underneath is bare clay with a black crackle drawing burned into it. The pot is the record of what came off. Here is the full method, both versions of it, what each layer is actually doing, and every way it goes sideways.
Written for members of The Clay Hole and useful to anybody with a raku kiln. All eight videos on this page belong to somebody else, every one is free, and nothing loads from YouTube until you press play.
Written for members of The Clay Hole and useful to anybody with a raku kiln. Both videos belong to somebody else, both are free, and nothing loads from YouTube until you press play.
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The whole idea
You are building a shell, so that smoke can only get through the cracks in it.
The one question that decides everything
Can the shell come off cleanly? If any glaze touched bare clay it fused there and it is never coming off. If the slip went on too thin the glaze reached through it and did the same. Every other decision on this page is downstream of keeping glaze and pot from ever meeting.
A burnished pot gets a coat of resist slip, then a thin crackle glaze on top of the slip. In the fire the glaze crazes. In the smoke can, carbon runs down those craze lines, through the slip, and stains the clay underneath. Then you wash the whole shell off and the stains are the artwork.
The slip is a release layer and nothing else. It is there so the glaze cannot bond to the pot. The glaze is a crack pattern generator and nothing else. It is there to decide where the smoke gets in. Neither one is decoration, and neither one survives.
What you need: a thin-walled bisqued pot in a grogged clay body, terra sigillata, resist slip, a raku crackle glaze, tongs, a metal can with a tight lid, and a pile of newspaper or sawdust.
You are reading the Nutshell Version. The switch above opens the long one, which covers the layer-by-layer diagram, the one-layer method, terra sigillata, slip and glaze thickness, firing temperatures, and nine ways this goes wrong.
The method
Naked raku, in seven moves
This is the two-layer method, which is the one nearly everybody starts with and the one that gives you the most control over the pattern.
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Build it thin, round and smooth
Even walls, no sharp corners, no thin rims, no handles. A grogged body survives the temperature swing. Sand the leather-hard surface smooth, because carbon shows every tool mark you leave behind.
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Terra sigillata, then burnish
Two or three thin coats on bone-dry clay, buffing each one with a soft cloth or a plastic bag while it still looks damp. A closed, polished surface takes sharp black lines. An open one takes fuzzy grey ones.
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Bisque it, then keep it clean
Dust is the enemy from here on. Blow the pot off and wipe it with a barely damp sponge before anything goes on it, because dust stops slip sticking and turns into black specks later.
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Two or three even coats of resist slip
Brush, pour or dip. Cover the whole outside with no gaps and no overlaps you can feel. Let each coat lose its shine before the next. Even is the entire goal here; thin patches go black and thick patches flake off early.
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One thin coat of crackle glaze over the slip
Thin and even. It must never touch bare clay anywhere, including the foot. Thinner glaze gives you tight fine crackle, thicker glaze gives you big sparse crackle, and there is no third setting.
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Fire to roughly 1400 degrees, then pull
Take it slow to about 1000, then let it climb. You are looking for the glaze to go glossy with a faint orange-peel texture. The look beats the pyrometer every time.
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Wait for the ping, then smoke it and seal the lid
Hold the pot in the air about thirty seconds until you hear the glaze start to tick and crackle. Into the newspaper, lid on tight, fifteen minutes, no peeking. Let it cool, then take the shell off under running water with a plastic rib.
Naked Raku ~ The Full Monty
ArranEye
If you only watch one thing, watch this one. It runs the entire process end to end without skipping the boring parts, which are the parts that decide whether the shell comes off. Watch it on YouTube.
Naked Raku. Two techniques
Foelber Pottery
Two minutes, two different ways of getting smoke into a hot pot. Useful for seeing how differently the same pot can be treated once it leaves the kiln. Watch it on YouTube.
Why this page reads like this
Video shows you the hands. Reading is what you still have three weeks later.
Read a section, watch somebody do it, then go and do it yourself. Or watch first and read after. Both work fine. Doing only one of the two is how people end up standing next to a smoking can with no idea why every pot came out grey.
Some of this cannot be written down. How thick a coat of slip actually looks going on. How fast somebody moves from the kiln to the can. What the glaze sounds like when it starts to craze, which is the cue for the single most important thirty seconds in the whole process. You have to watch a person do those, and that is what film is unbeatable at. It is why there are eight videos here.
But film is a miserable reference. You cannot skim it. You cannot jump to the bit about slip thickness. You cannot scrub a timeline with slip on your fingers, and you cannot search it a month later when you have forgotten whether the glaze goes over the sigillata or the slip. Text holds still. You set the pace, you re-read the one line you needed, and setting your own pace turns out to be most of what makes a thing stay in your head.
So this page is deliberately both, and it is built to be held up on a phone next to a wet table. The lists are short on purpose. Nothing loads from YouTube until you press play, which also means it opens fast on studio wifi.
None of these videos are ours. Every one is somebody else's work, credited by name and channel, and pressing play sends the view to their channel where it belongs.
What is actually happening
Four layers, and only one of them survives
Naked raku is named for what is missing at the end. There is no glaze on a finished piece. There is bare, unglazed clay, and a black crackle pattern that was smoked into it while something else was standing in the way.
- The crackle glaze. A thin low-fire glaze whose whole job is to craze into a pattern as it cools. It never touches the pot.
- The resist slip. A release layer of raw clay. The glaze cannot bond through it, which is the only reason any of this comes apart later.
- The terra sigillata. A polished skin of ultra-fine clay particles. Optional, and it is the difference between crisp lines and soft ones.
- The clay body. The only layer still on the pot when you are done. Porous, unglazed, and ready to take carbon.
- The craze lines. The glaze cracks as it cools, and the cracks run down through the slip. These are the only doors into the pot.
- The carbon. Smoke follows the cracks, hits the clay and stains it black. Wherever the shell held, the clay stays pale.
- The shell comes off. Slip and glaze lift away together, sometimes on their own, usually with water and a rib. That is the reveal.
Everything you apply is scaffolding
This is the mental flip that makes naked raku click. You are not glazing a pot. You are building a temporary mask, deciding where it will crack, and then throwing it away. Judge every coat you put on by one question: is this going to come off cleanly and leave the line I wanted?
Naked Raku ~ The Full Monty
ArranEye
The best single overview on the internet, and the most watched. Every stage in order, including the unglamorous ones. Watch it once before you read any further and the rest of this page will make more sense. Watch it on YouTube.
Two methods, one idea
The two-layer method and the one-layer method
Both are naked raku. Both end with a shell coming off a bare pot. They differ in what makes the cracks: a glaze that crazes in the cooling, or a slip that cracks itself while it dries on your bench.
| Two-layer | One-layer | |
|---|---|---|
| What goes on | Thin resist slip, then a thin crackle glaze over it. | A single thick resist slip. No glaze at all. |
| What cracks | The glaze crazes as the pot cools, and the cracks carry on down through the slip. | The slip shrinks and cracks on its own while it dries, like mud drying on a road. |
| The look | Fine, even, all-over crackle. Reads as a drawn net. | Bold, irregular, wandering. Reads as something geological. |
| How much you control | A lot. Glaze thickness sets the scale of the crackle, so you can aim. | Some. Slip thickness and drying speed nudge it. The pattern is mostly its own idea. |
| Where it goes wrong | Glaze finding bare clay and fusing there, so the shell will not release. | The shell falling off before the pot ever gets to the kiln, or during the pull. |
| Start here if | You are new. More steps, but far more predictable, and easier to diagnose. | You have a few firings behind you and you want the pattern to surprise you. |
Everything below assumes two layers
Slip, then glaze. It is the version most people teach, the version most of these videos show, and the version where a bad result tells you which step caused it. The one-layer method is the same fire and the same can, with a thicker slip and much gentler hands.
Naked Raku. Two techniques
Foelber Pottery
Two minutes and no talking, which is the right length for this. Two different treatments of a hot pot, side by side, so you can see how much the post-fire handling changes the result. Watch it on YouTube.
The pot has to survive first
Raku breaks pots. Design for that before you design for the pattern.
The shape test
Look at your piece and find the place where two thicknesses meet, or where a wall turns a hard corner. That is where it will crack. If you cannot find one, it is a good raku form.
A raku pot goes from room temperature to around 1400 degrees and back down in under an hour, with the violent part happening in about ninety seconds. Nothing about that is gentle. Clay expands when it is heated and contracts when it cools, and if one part of the pot is doing that faster than the part next to it, the pot solves the disagreement by splitting.
Thin and even. Thin walls change temperature all the way through at roughly the same rate. Thick walls have a hot outside and a cool inside pulling against each other. A wall that is thin in one place and thick in another is worse than either.
Round and simple. Bottles, bowls, closed forms, spheres. No sharp corners, no delicate rims, no handles, no lids, no attachments. Every join and every angle is a stress point, and this is not the firing where you get away with them.
An open, grogged body. Grog is coarse material that gives cracks somewhere to stop. It also keeps the body porous, which is what lets carbon in later. At The Clay Hole the two clays we send to raku are B-Mix with Grog and Berlin Gray. Porcelain is a beautiful surface and a bad bet in a raku kiln.
Smooth, before it ever dries. Carbon lands on a surface and shows you everything about it. Throwing rings, sponge drag, a chattery trim, a fingerprint in the foot: all of it reads. Sand or rib the surface at leather hard, then again lightly at bone dry.
Small, at least at first. Something you can lift with tongs in one hand and swing into a can without thinking about it. Big pots make the pull slow, and a slow pull is a cold pot, and a cold pot takes no carbon.
Worth reading alongside this: our pages on wall thickness and proportion and on throwing enclosed forms, which are the friendliest raku shapes there are.
Terra sigillata and burnishing
The polish is what makes the line sharp
You can skip this step. Plenty of good naked raku has no terra sigillata on it. What you get instead is a softer, greyer, fuzzier line, because carbon spreads sideways into an open surface and stops dead at a closed one.
What terra sigillata actually is
Clay and water with a deflocculant stirred in, left to separate for a day or two. The heavy particles sink, the middle layer is nothing but the very finest ones, and that middle layer is the sigillata. You siphon it off and throw the rest away. It is not a glaze and it does not melt. It is a skin of clay so fine it can be polished.
Why it matters here specifically
Carbon staining is a surface event. On a rough, open bisque the smoke wanders and you get a grey blur where you wanted a black line. On a burnished sigillata surface the carbon has nowhere to spread, so the craze pattern transfers almost exactly. It also makes the pale areas properly pale instead of dusty.
- Wait for bone dry. Sigillata goes on greenware, not on bisque. On a damp pot it will not polish and it can lift the surface.
- Two to four thin coats. Thin is the word that matters. A thick coat cracks and flakes off in the bisque, which is worse than no coat at all.
- Buff each coat while it is still going matte. A soft cloth, a piece of an old plastic bag, or a smooth stone. You are chasing the moment the shine appears, which is usually within a minute of the coat losing its wet look.
- Work in small areas. A whole pot at once will dry past the burnishing window before you get around it.
- Keep the bisque low. Sigillata loses its sheen if the bisque runs hot. The Clay Hole bisques everything to cone 05, which is on the warm end of what naked raku people usually use and still works. If your pale areas come out chalkier than you hoped, this is one of the reasons.
- Do not sigillata the foot. Or anywhere the pot rests. A polished foot skids on tongs, and skidding is how pots get dropped.
How to Mix and Apply Terra Sigillata for Burnishing Pottery | Sumi von Dassow
Ceramic Arts Network
Mixing and settling it, then applying and buffing it. Watch how thin the coats are and how quickly she moves after each one, because the burnishing window is much shorter than most people expect. Watch it on YouTube.
The resist slip
The layer that decides whether any of this works
The resist slip is a release layer. Its only job is to sit between the glaze and the pot so the two never bond. Get it even and the shell lifts away in sheets. Get it patchy and you spend an evening with steel wool arguing with a pot that has already won.
What to make it from
A fire clay or a stoneware body, mixed with water. Different potters swear by different fire clays and the differences are real, because how much the slip shrinks and how well it clings are exactly the properties you are tuning. Charlie and Linda Riggs bought samples of every fire clay they could get hold of before settling. If you are starting out, your own throwing body thinned down works and is free.
How thick to mix it
For the two-layer method, about the consistency of heavy cream. For the one-layer method, considerably thicker, because there you want it to shrink and crack on the bench. Test on a scrap of bisque before you commit a pot to it.
Putting it on
- Clean the bisque first. Blow the dust off, then wipe with a barely damp sponge. Dust stops slip adhering, and every place it does not adhere becomes a black speck later.
- Warm the pot slightly. Not hot. Slightly warm bisque pulls the slip in and holds it. A cold pot lets it sit on top and slide.
- Two or three thin coats, not one thick one. Brush, pour or dip. If you dip, in and out in one movement so the coat is the same everywhere.
- Let each coat lose its shine before the next. Going over a wet coat drags it and leaves you thin patches you cannot see.
- Cover the whole outside. Every gap is a place the glaze will find bare clay and fuse to it. Pay attention to the foot, the rim and anywhere a curve turns away from you.
- Stir with a stick, not a drill. A paint mixer whips microscopic air bubbles into the slip and every one of them is a black dot on the finished pot. If you have already used a drill, let the bucket settle a day and stir it by hand before use.
- Mask before you slip, if you want solid black. Tape off a shape, slip the pot, peel the tape carefully. Bare clay under the tape smokes completely black, and it sits beautifully against the crackle.
Even beats thick, every single time
Thin spots let the glaze reach the clay and weld the shell on. Thick spots shrink harder than the ones next to them and flake off before the pot ever sees the kiln, exposing clay that then goes black. Both failures come from the same place, which is a coat that varies. Hold the pot up to a raking light and look across the surface rather than at it.
Learn Naked Raku - Don Ellis & Randy Brodnax at Ceramic Services
Zenka Caro
Two instructors who have been teaching this for decades, working through slip and glaze in front of a room. Sixteen minutes, and the most useful part is watching how casually experienced hands treat a step you are probably being precious about. Watch it on YouTube.
The crackle glaze
One thin coat, and it never touches the pot
This glaze is not there to look like anything. It is a crack pattern generator. It goes on over the slip, it crazes as the pot cools, and those craze lines are the only route smoke has into the clay. Then it leaves.
Thickness is your only dial
Thin glaze gives tight, fine, closely spaced crackle. Thick glaze gives big, bold, widely spaced crackle, and past a point it stops crackling properly and gives you shadowy blank patches and dots instead. Everything else about the pattern is chance. This one thing is a choice.
What to use. The classic base for this is a two-ingredient low-fire glaze, roughly two parts Ferro frit 3110 to one part Gerstley borate. Charlie and Linda Riggs, Don Ellis and Randy Brodnax have all worked with versions of it for decades, and people keep coming back to it because it crazes cleanly and releases cleanly. A commercial clear raku crackle glaze does the same job out of a jar.
Mix it and use it fast. Gerstley borate thickens in the bucket within a minute of stirring, so pour right after mixing or stir constantly if you are doing several pots. The same air-bubble warning from the slip applies here: bubbles become dots.
One thin, even coat over the slip. Pour it on larger pieces, brush it on small ones. Do not go back over a spot you already covered.
Nowhere near bare clay. Not the foot, not a chip, not a place where the slip got thin. Glaze that reaches the pot fuses to it at temperature and that patch of shell is permanent. This is the single most common reason a naked raku pot fails.
Draw into it if you want to. Once the glaze is touch dry you can scratch a line through the glaze and slip with a sharpened wooden point. Smoke pours straight into that channel, so whatever you draw comes out as a firm black line inside the crackle. Go gently, because scratching into the clay itself gives you a groove you cannot undo.
Ceramics Tutorial by Paul "Buddy" Terrell, Naked Raku, Episode 5: Glazing
Artspace Gallery
Part of a six-episode series that follows one body of work from the first idea to the fire. This is the glazing episode, and it is worth watching just for how little glaze actually goes on. Watch it on YouTube.
Firing and the pull
Slow to a thousand, then let it run
Naked raku fires nowhere near as hot as a normal glaze firing. You are looking for somewhere around 1400 degrees Fahrenheit, and the exact number matters less than what the glaze looks like when you get there.
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Load a dry pot into a cold or barely warm kiln
Any moisture left in the slip or glaze turns to steam and blows the shell off, or the pot with it. If a piece has been sitting in a damp garage, warm it slowly on top of the kiln first.
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Take it slowly to about 1000 degrees
This is the stretch where thermal shock happens. Once the pot is through it and everything is heated evenly, you can climb as fast as the burner will go.
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Watch the glaze, not the pyrometer
Somewhere in the region of 1350 to 1450 the glaze goes glossy and develops a faint orange-peel texture. That texture is the cue. Different people fire to different numbers with the same glaze and get the same result, because they are all reading the same surface.
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Fire one piece at a time if you can
Not a rule, but it is what most naked raku people end up doing. The pull is the moment everything hinges on, and handling one pot properly beats rushing four.
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Pull at the widest part of the form
Tongs around the belly, never on the rim. The rim is the thinnest part of the pot and the part most likely to crack under a point load, and a dropped pot at 1400 degrees is a genuinely bad afternoon.
This is the part with real risk in it
Open flame, an unshielded kiln, tongs full of glowing pottery and people moving around each other. Long sleeves, long pants, closed-toe shoes, hair tied back, gloves and eye protection, and never alone. At The Clay Hole this only ever happens at a workshop, outdoors, after a safety meeting that everybody attends. Read the raku safety rules and certification page before you come to one.
Ceramics Tutorial by Paul "Buddy" Terrell, Naked Raku, Episode 6: Firing
Artspace Gallery
The firing episode of the same series, so you see the same pots you watched him glaze go into the kiln. Watch the handling more than the kiln. Watch it on YouTube.
Smoke, and the can
Thirty seconds in the air, then starve it of oxygen
Everything you have done so far was preparation for about fifteen minutes inside a sealed metal can. This is where the pattern is actually made, and it is the stage people rush.
The pause before the can
Hold the pot in the open air for roughly thirty seconds to a minute after it leaves the kiln. You are listening. As the glaze contracts it starts to tick and crackle, and that sound is the craze network opening. Too soon and the cracks are not there yet, so the smoke has nowhere to go. Too long and the pot has cooled below the temperature where carbon will drive into the clay, and you get grey.
What goes in the can
Newspaper is the standard and it is standard because it works. Sawdust, wood shavings, straw and dry leaves all do the same job at different speeds. A generous nest underneath, the pot on top, then more over it. It will catch instantly. That is expected and it is fine.
- Seal the lid, properly. Oxygen starvation is the entire mechanism. The fire consumes the oxygen in the can, then starts pulling it out of anything it can reach, and the free carbon it leaves behind is what stains your pot. A leaky lid means a fire that keeps breathing, and a pot that comes out grey and disappointing.
- Ten to twenty minutes, and do not lift the lid. Every peek admits oxygen and burns off carbon you already made. Set a timer and walk away from it.
- Never quench it in water. Thermal shock will crack the pot, and the water rinses away carbon that has not settled yet. Let it cool in the can or on a shelf.
- Longer is not automatically better. Once the pot has dropped below carbon-taking temperature, more time in the can does nothing except make the shell harder to get off.
- Expect the shell to look wrong. It comes out black, blistered, sooty and ugly. That is the correct appearance for something you are about to throw away.
Naked Raku with Chris Neiman
Chestertown RiverArts
Twelve minutes covering the kiln through to the reduction can. This is the one to watch for timing: how long the pot sits in the air, and how quickly the lid goes on once it is in the combustibles. Watch it on YouTube.
Taking the shell off
The best part, and the easiest one to ruin in a hurry
Sometimes the shell pops off in the can all by itself and the pot is sitting there finished. Usually it needs help. Either way, the pot underneath is fragile in a way a normal fired pot is not, so nothing you use should be harder than the clay.
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Wait until you can hold it comfortably
Working on a pot that is still hot means working fast and rough, and it means putting cold water on hot clay. Neither of those ends well. Let it come down to room temperature.
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Work under running water
Water softens the raw slip and floats the loosened shell off instead of grinding it around the surface. It also keeps the dust down, which matters, because dry silica dust is not something to breathe.
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Plastic ribs, wooden tools and a stiff brush
Nothing metal against the bare clay. A plastic rib for sheets that are already lifting, a stiff nylon brush for the stubborn bits, and fine steel wool only where the surface is proving genuinely difficult and you accept the risk.
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Do not scrub the pattern
The carbon lives in the top fraction of a millimeter of clay. Aggressive scouring takes the artwork off along with the shell. If a patch will not budge, come back to it after it has soaked rather than leaning harder.
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Dry it completely, then look at it in daylight
Wet clay looks darker and more contrasted than it will when it dries. Give it a day before you decide how the firing went, because a pot that looked flat and grey when wet often comes back.
Say this part out loud
A naked raku pot is porous, unvitrified, low-fired and unglazed. It is not food safe, not watertight, not microwave safe and not dishwasher anything. It will hold dry flowers and it will hold your eye across a room. It will not hold coffee. Anybody you give one to should be told that.
Finishing, if you want to
Nothing at all. Perfectly legitimate. A clean burnished surface has a soft sheen of its own and plenty of potters stop here.
Paste wax. A thin coat of clear furniture or museum wax, buffed. It deepens the blacks, evens out the pale areas and gives a low sheen. It is reversible, which is the reason to prefer it.
Acrylic sealer. A matte spray sealer protects the carbon from handling and does not yellow. It is also permanent, so test it on something you do not love first: some sealers darken the pale clay more than you expect and flatten the contrast you spent all day making.
Do not fire it again. Carbon burns out. A naked raku pot put through any oxidizing firing comes out as a plain pale pot with nothing on it at all, which is a lesson people usually only need once.
Naked Raku Process
Rihab Raku
Another full run through the process, and a good second opinion on everything above. Compare the way the shell is removed here against the other videos on this page, because that step varies more between potters than any other. Watch it on YouTube.
The whole thing on one screen
Nineteen lines, for a phone at a wet table
Nine lines, for a phone at a wet table
No explanation, no reasoning, nothing to scroll past. Just the order of operations. Print it from the button at the top of the page if you would rather have paper that does not mind wet hands.
Just the order of operations. Print it from the button at the top of the page if you would rather have paper that does not mind wet hands.
Before the fire
- Thin, even walls. Round form. No handles, no lids, no sharp corners.
- Grogged, open clay body. B-Mix with Grog or Berlin Gray.
- Smooth the surface at leather hard, then again at bone dry.
- Two to four thin coats of terra sigillata on bone-dry clay, buffing each one as it goes matte.
- Bisque. Cone 05 at the studio.
At the table
- Blow the dust off, wipe with a barely damp sponge, warm the pot slightly.
- Two or three thin, even coats of resist slip over the whole outside.
- Let each coat lose its shine before the next one.
- Check it in raking light for thin patches. Fix them now.
- One thin, even coat of crackle glaze over the slip. Never onto bare clay.
- Scratch any drawing through the glaze and slip while it is touch dry.
- Dry it fully before it goes anywhere near heat.
At the kiln
- Slow to about 1000 degrees, then climb.
- Pull when the glaze is glossy with a faint orange-peel texture, around 1400.
- Tongs on the widest part of the pot, never on the rim.
- Hold it in the air about thirty seconds. Listen for the ticking.
- Into the newspaper, cover it, seal the lid tight.
- Fifteen minutes. No peeking. No water.
After
- Cool to room temperature, then take the shell off under running water with a plastic rib. Dry it a full day before you judge it.
- Thin even walls, round form, grogged clay body.
- Terra sigillata on bone-dry clay, buffed. Then bisque.
- Dust off, wipe, warm the pot slightly.
- Two or three thin even coats of resist slip over the whole outside.
- One thin coat of crackle glaze over the slip. Never onto bare clay.
- Slow to 1000, then climb to about 1400 and glossy orange peel.
- Pull at the widest part. Thirty seconds in the air, listening for ticking.
- Into the newspaper, lid sealed, fifteen minutes, no peeking.
- Cool fully, then shell off under running water with a plastic rib.
When it goes wrong
Nine ways this goes wrong, and what caused each one
The three that get everybody first
Naked raku has a low success rate early on and a good one later, and the reason is that almost every failure has one specific cause you can point at. Here is the list, roughly in order of how often we see each one.
Almost every naked raku failure has one specific cause you can point at. These are the three that show up on a first firing.
The shell will not come off
Glaze reached bare clay somewhere and fused to it. Either the slip went on too thin, or there was a gap in it, or glaze ran onto an unslipped foot. Less often, the firing went hot enough to start sintering the slip itself. Next time: more slip, checked in raking light, and keep glaze well clear of anything unslipped.
No black lines, just a grey haze
Not enough reduction. The lid did not seal, or the pot sat in the air too long and cooled below the temperature where carbon drives in, or somebody lifted the lid to look. Next time: seal it properly, get it in faster, and set a timer instead of peeking.
The whole pot came out black
The shell left before it was supposed to. It flaked off in the kiln, or came away during the pull, or the slip cracked and lifted on the bench beforehand, and smoke reached the entire surface. Next time: thinner, more even slip coats and a gentler pull.
Black dots all over it
Air bubbles, in the slip or the glaze or both. A drill or paint mixer whips them in. Dust on the bisque does the same thing by stopping the slip adhering in tiny spots. Next time: stir with a stick, let a drill-mixed bucket settle for a day, and clean the bisque before anything touches it.
Huge sparse crackle when you wanted fine
The glaze went on too thick. This one is purely a thickness dial and it is the most controllable variable on the whole page. Next time: thinner coat, and test two or three thicknesses on scrap bisque so you can see the range before you commit.
The pot cracked
Thermal shock. Walls too thick, or thick in one place and thin in another, or a sharp corner, or a handle, or too fast through the low end of the firing, or water on a hot pot. Next time: thinner and rounder, slow to 1000 degrees, and no quenching, ever.
The shell fell off before the firing
Slip on too thick for a two-layer piece, or it dried too fast, or the bisque was dusty and the slip never really grabbed. Next time: more coats, each one thinner, dried at a sensible speed, on a clean pot.
The lines washed away in the sink
The carbon was sitting in the slip layer rather than in the clay. Usually that means the pot was already too cool when it went into the can, or the body was too dense to take carbon at all. Next time: shorten the pause before the can, and use a more open clay body.
Grey smudges over the pale areas
Smoke found a way under the shell, usually at a chip, a bare patch or a place where the shell lifted in the can. Not really a failure, and a lot of people come to like it. If you do not, the fix is the same as always: an even, unbroken slip coat.
Expect to lose some
Nobody gets a full rack of good pots out of an early naked raku session, and the people who have been doing this for thirty years still lose pieces. Bring more than you need, make peace with that before you get there, and take notes on every single pot: slip coats, glaze thickness, pull temperature, seconds in the air, minutes in the can. Four firings of notes will teach you more than anything on this page.
Naked raku at The Clay Hole
None of this happens in the studio. It happens at a workshop, outdoors, at night.
Everything arrives finished
Pots come to a raku workshop bisqued, slipped and glazed, ready to go straight into the kiln. There is no glazing table out there, no sink, and no do-overs. Whatever is on your pot when you get out of the car is what gets fired.
Our kilns are electric and they fire glaze to cone 5½, which is cone 5 with a twelve minute hold. Raku is a different animal entirely: a small gas kiln, an open flame, a temperature less than half of that, and a pot that comes out while it is still glowing. It is not something that can happen indoors on Pony Express Road, and it is not something anybody should try alone in a garage.
So we run it as workshops. Everyone attends a safety meeting in person before anything is lit, everyone signs a fresh waiver every time, and everyone stays through cleanup. There is a safety and certification page that walks through the rules and the choreography of an unload, which is worth reading whether or not you take the card.
Two studio rules that matter for naked raku. One glaze family per pot, and never mix brands on a single piece: know exactly what is on each one before it goes in. And raku glazes never go into a studio kiln, because they are formulated for a fraction of the temperature and they will run off your pot and onto a shelf.
The clay is the easy part. B-Mix with Grog and Berlin Gray are both on the shelf, and both take the thermal swing well. Berlin Gray is a dark body, which changes the whole game: your pale areas are not pale, and the contrast comes from tone rather than from black against white.
Questions we actually get
The ones that come up every workshop
Do I have to use terra sigillata?
No. It is the difference between a crisp line and a soft one, not the difference between working and not working. Plenty of naked raku is done straight onto plain bisque and it has a gentler, hazier look that some people prefer on purpose. If your first firing is about learning the slip and the glaze, skip it and add it later.
Can I naked raku a pot that has already been glaze fired?
No. A pot that has been through a cone 5½ glaze firing is vitrified, which means it is dense and closed and there is nowhere for carbon to go. It is also under far more thermal stress in a raku kiln than a bisque pot is. Naked raku starts from bisqueware, always.
Is a naked raku pot food safe?
No, and not in a borderline way. It is unglazed, unvitrified, porous and low fired, and the surface is a layer of carbon. Nothing goes in it that you plan to eat or drink, it does not hold water, and it does not go in a dishwasher or a microwave. Dry goods and decorative use only.
Can I get color into naked raku?
Some, and not the way you get color from a glaze. Terra sigillata can be tinted with stains and oxides, so your pale areas can be a warm ochre or a soft blue-grey rather than white. Colored slips layered under the resist do a similar thing. But the black is carbon, and carbon only comes in one color, so the crackle itself stays black no matter what.
Why are my crackle lines so far apart?
The glaze is too thick. Thicker glaze crazes into fewer, bigger sections; thinner glaze crazes into a tight fine net. It is the most reliable relationship in the whole process, which makes it the easiest thing to aim once you have seen a couple of examples. Glaze three scrap bisque tiles at three different thicknesses and fire them together.
Do I need to be certified to come to a raku workshop?
No. Nobody is turned away for not having the certification card, and you can register, show up, listen to the safety meeting and fire your pots without it. What is not optional is the safety meeting itself, and being there for all of it. The certification page mostly exists so you know what is about to happen before it happens.
How many pots should I bring?
More than you want to come home with, and all of them small enough to handle easily. Early naked raku loses pieces, and one pot means one shot at a process with about six independent ways to go wrong. Check the details for the workshop you are registered for, because there are limits on how much total width each person can bring.
One more thing
The pot you get is the one the fire decided on
Go and read the long version if you want the why
Everything on this page is about narrowing the odds. You control the wall thickness, the polish, the slip, the glaze thickness, the temperature and the seconds. You do not control where the glaze decides to crack, and that is the entire appeal. Wash a shell off a pot once and you will understand why people keep driving out to a field at midnight to do it.
That was the short version: enough to walk into a raku workshop knowing what you are doing and why. The switch at the top of the page opens the full one, with the layer diagram, the one-layer method, terra sigillata, glaze thickness, and nine ways this goes wrong.
Raku safety and certification
Every rule, the choreography of an unload, and the card. About fifteen minutes.
The studio calendar
Workshops, classes and events, including when the next raku firing is happening.
What a kiln firing actually does
Why a raku pot and a cone 5½ pot are completely different objects.
Throwing enclosed forms
Closed, round shapes are the friendliest thing you can put in a raku kiln.
Engobes, and what they are for
The other slip-family surface, and how it differs from a resist slip.
Clay Hole University
Every lesson we have written, sorted into departments, with quizzes.