Glaze and firing

Reglazing and Refiring: Rescuing a Bad Result

A disappointing pot is not a finished pot. Most glaze faults can be fired again, and a lot of them come back better than the original would have been. Here is what is worth rescuing, what is not, how to get glaze to stick to a glassy surface, and the habits that keep a refire from making things worse.

You can refire most glaze faults. The hard part is getting new glaze to stick to a fired glassy surface, and the answer is to warm the pot and build it in light coats. Crazing, cracks and warping are things a refire will not fix.

What to rescue, and what to let go Getting glaze to stick to glass Three videos, none of them ours
The route that works What a refire cannot fix Three ways it goes wrong
Illustration of a bearded potter in a studio brushing glaze onto a vase on a banding wheel, with a kiln behind him
Jump to a section
What is worth rescuing What a refire will not fix Getting glaze to stick to glass Doing it, step by step The firing itself The risks of a refire How it works here What goes wrong The whole idea, quickly The route that works Three ways it goes wrong Questions we get asked Keep going

What to rescue, how to get glaze to stick, and what a refire cannot fix.

The whole idea

The problem is that glass is not thirsty

Glazing bisque is easy because bisque is porous. It pulls the water out of the glaze on contact and the powder stays behind, stuck to the pot.

A fired pot has no porosity left. The glaze layer is glass. Brush wet glaze onto it and the water has nowhere to go, so it sits there, slides around, and falls off in sheets when it dries.

So every technique on this page is a way of solving that one problem: make the surface take the glaze, or make the glaze dry before it has a chance to run.

Start to finish

The route that works

Seven steps, applying a brushing glaze over an already fired surface.

Can You Refire Already Glazed Pottery? YES!!! Kara Leigh Ford
  1. Decide it is worth it. A refire costs another firing slot and can still fail. Some pots are better let go.
  2. Clean the surface. Wash it over a bucket, never down the sink, let it dry fully, then wipe with rubbing alcohol. Any grease and the glaze crawls off.
  3. Warm the pot. A hair dryer or a warm oven at home, or sunshine. In the studio, ask an instructor what we have for warming. Warm ceramic flashes the water out of the glaze and makes it grip instead of slide.
  4. Stir the glaze well and keep the coats light. A cold pot is the most common reason this fails, and thick glaze is another.
  5. Build it in light coats, drying between each. Thin coats beat one thick one.
  6. Keep it off the foot by a generous margin. A refired glaze is more likely to run than the first coat was.
  7. Same cone as the original. It goes back in at cone 5½ with everything else.
If it went wrong

Three ways a refire goes wrong

The glaze slid straight off

Cold pot, thick glaze, or both. Wet glaze on non-porous glass has nothing to grip. Warm the pot and build it in light coats.

It ran onto the shelf

Two layers of glaze means twice the flux and a much more fluid melt. A refired pot needs a wider clear margin at the foot than it did the first time, and a kiln cookie under every piece is the rule here.

It came out blistered

The second firing reheated a glaze that had already released its gases, and the trapped bubbles had nowhere to go. Thinner coats help, and some pots just will not take a third trip.

Triage

What is worth rescuing

Not every disappointing pot deserves a second firing. Choosing the right pots saves kiln space and saves you from a worse version of the same pot.

How to RE-GLAZE your failed pots!!! Jonthepotter Eleven minutes. The description says it is about refiring pots that did not come out as expected, and the chapters cover assessing the damage, techniques, new glaze coats and the results.
  1. Dry, rough glaze. The best candidate there is. Here it usually means the coat was thin, since every load gets the same firing, so one more coat and another trip often finishes the job.
  2. Too thin, patchy or starved. Another coat over the top usually fixes it outright, and this is the most common successful refire.
  3. A color you dislike. Often fixable. Glaze over it, and expect the result to be darker and deeper than the new glaze would be on its own.
  4. Bare spots and crawling. Worth a go. Clean carefully, because the cause was usually grease or dust that is still there.
  5. Pinholes. A refire sometimes heals them. Ask an instructor first, because some get worse.
  6. Somewhere between fine and disappointing. This is the judgment call. A refire has a real failure rate, and a pot you are lukewarm about can come back worse. Sometimes the right call is to use it and make another.

The reframe worth having

A refire is not a repair that restores a pot to what you intended. It is a new firing with new variables that happens to start from a glazed pot. Treat it as another attempt rather than a correction and the results stop feeling like failures.

Let these go

What a refire will not fix

Knowing the difference between a fault and a flaw saves a lot of wasted effort.

Crazing

The fine web of cracks is a mismatch between how much the glaze and the clay shrink as they cool. Another firing does not change either material, so the crazing comes straight back. The fix is a different glaze or a different clay, on the next pot.

A cracked pot

A crack in the clay body will not close. Heat opens it further, and a pot that survived one firing with a crack may come apart in the second. Not worth the shelf space or the risk to other work.

A warped form

Warping happened at temperature, when the pot was soft. Going back up does not straighten it and can make it worse, because the whole thing softens again with gravity still pulling.

S-cracks and structural faults

Anything that came from the making rather than the glazing. A second firing only ever addresses the surface.

Bloating

Blisters in the clay body itself, from overfiring or from impurities gassing. Refiring usually makes it worse.

A shape you do not like

Obvious when written down and surprisingly common as a hope. No amount of glaze rescues a form. Make another one; you are better at it now than you were then.

The actual difficulty

Getting glaze to stick to glass

This is the whole technical content of reglazing. Everything else is ordinary glazing.

Reglazing pots - can we fix some old mistakes? Pottery by Kent Four minutes. One potter reglazes some old pots with a clear glaze to cover defects, and the chapters take rough spots, crawling and pinholes in turn.
  1. Warm the pot. This is the big one. A pot at 120 to 150 F flashes the water out of the glaze on contact, which is the porosity you no longer have. A hair dryer or a low oven at home, or a sunny windowsill. In the studio, ask an instructor what we have for warming. Warm, not hot enough to burn your hands.
  2. Clean it properly first. Wash, dry completely, then wipe with rubbing alcohol. Skin oil is the reason most reglazed pots crawl.
  3. Use the glaze as it comes. Do not add water to a jar. A thick layer on glass has nothing holding it up, so if a glaze looks too thick, ask an instructor.
  4. Build it in light coats. Three thin passes with drying between them will stay put where one heavy pass slides off in a sheet.
  5. Brushing glazes are far easier than dipping. They carry gums that help them grip, which is exactly the problem you are solving. Dipping a fired pot mostly does not work.
  6. Scuffing the surface helps a little. A green scouring pad or a wet diamond pad gives the glaze some tooth. Work wet over a bucket, never dry, with safety glasses and at least an N95. It is optional rather than essential.
  7. A glaze that still refuses to stay is a question for an instructor. Brushing glazes already carry gum, and nobody adds anything to a jar.
Doing it

Step by step

How to Fix a Glaze Fail Three Little Potters Thirty-five minutes, which is long. The description says one potter compares glue, hairspray, sanding and heating the pots, then shows the results. We do not teach the glue or hairspray methods here.
  1. Work out what went wrong first. Dry, too thin, crawled, pinholed. The fault decides whether you add glaze or just fire it again. Show an instructor first.
  2. Wash the pot over a bucket, never down the sink, and dry it, then wipe it down with rubbing alcohol, keep the alcohol away from flame, and let it dry completely before you warm it. Stop touching the surface you are about to glaze.
  3. Warm it through. Not just the surface. A pot warmed for a few minutes holds the heat long enough to glaze the whole thing.
  4. Stir the glaze well, then work quickly while the pot is still warm. If it looks thick, ask an instructor before you add anything.
  5. Apply light coats, letting each flash off before the next. If a coat starts sliding, stop, let it dry, and come back.
  6. Leave a wider margin at the foot than you normally would. At least a quarter inch more.
  7. Let it dry slowly and completely before firing. Water left under a new coat turns to steam in the firing and can blow the glaze off.
  8. Drop it off with a note on the ticket, so the staff who load the kiln can put it where a run will not damage anyone else's work. Put it on a kiln cookie first.
In the kiln

The firing itself

A refire is mostly an ordinary glaze firing with a pot in it that has already been through one.

  1. Same cone as the original. Ours go back to cone 5½ with everything else. Firing hotter to force a melt is how a rescue turns into a run.
  2. A slower climb helps, especially for pinholes and blisters, because it gives gases time to leave before the glaze seals over. Every load here runs the same schedule, so this is what to expect, not something to request.
  3. The hold matters more than usual. Time at temperature lets a reluctant melt finish and heal its own faults. You cannot ask for a longer hold here, because every load runs the same schedule.
  4. Expect the color to deepen. Two layers of glaze read darker and often more interesting than either alone. This is a feature more often than a problem.
  5. The glaze underneath melts again too. You are not adding a layer on top of a stable surface; you are melting both together. That is why the result is genuinely new rather than a patch.
  6. Diminishing returns after the second or third trip. Each firing is more heatwork on the clay body, and eventually the body starts to suffer before the glaze improves.
In a shared kiln

The risks of a refire

A refire is not free and it is not certain. Both of those matter in a shared studio, where a run affects more than your own pot.

  1. Running is the big one. Two glaze layers melt more fluidly than one. A glaze that behaved perfectly the first time can move on the second, and a run reaches the shelf, the kiln furniture and sometimes a neighbor's work.
  2. Blistering. Reheating a glaze that already released its gases can trap bubbles that never heal.
  3. The pot can crack. Every firing is thermal stress. A pot with a flaw you cannot see may not survive a second one.
  4. It might come back worse. Genuinely. A mediocre pot can turn into an unusable one, and that outcome is common enough to be worth weighing.
  5. It costs a firing. Kiln space, time and energy, for a pot that already exists.

The one rule that prevents most damage

Leave more clearance at the foot than you think you need, and assume the glaze will move. That single habit is the difference between a refire that fails quietly and one that welds a pot to a shelf.

At The Clay Hole

How it works here

Refires go through the same glaze firings as everything else, at cone 5½. There is no separate refire kiln and no special schedule.

  1. Put it on a kiln cookie and mark it a refire. Write on the ticket that it is a refire and leave it on the drop-off table. Staff load every kiln here, and the note changes where it gets loaded, which protects other people's work as much as yours.
  2. Leave a wide foot margin. Glaze close to the foot can weld the pot to its cookie.
  3. Firing is charged the same way as any other piece. A refire is a firing, so it is measured and billed like one.
  4. A piece that runs onto a shelf means a damaged shelf, and shelves are not cheap. That is the reason for the caution.
  5. If you are not sure whether it is worth refiring, ask. An instructor can look at the pot with you and tell you whether another trip is worth it.
Read this after a failed rescue

What goes wrong, and what caused it

The glaze slid off while you were applying it

Cold pot. Warm it through and work while it is still warm. This is the single most common reason people conclude that reglazing does not work.

It dried and then flaked off in sheets

Too thick. On a non-porous surface a heavy layer shrinks as it dries and has nothing gripping it. Lighter coats, and ask an instructor if the glaze itself looks thick.

Bare patches after firing

Crawling, from grease or dust on the surface. Clean with alcohol and then do not touch the area with bare hands.

It ran and stuck to the shelf

Two layers of flux, a more fluid melt, and not enough clearance. This is the failure that costs somebody money, which is why the margin rule exists.

Blisters and craters that were not there before

Gases trapped under a glaze that had already sealed. A slower climb and a hold help, but every load here runs the same schedule, so you cannot ask for them. Some pots simply will not take a second trip.

The crazing came back

It was always going to. Crazing is a fit problem between glaze and clay, and refiring changes neither. Take that one as information for the next pot.

Questions we get asked

The ones that come up at the tables

Can you refire already glazed pottery?

Yes, and it works far more often than people expect. The difficulty is not the firing, it is getting new glaze to stay on a non-porous fired surface. Warm the pot and build it in light coats.

How many times can a pot be fired?

There is no hard limit, and returns diminish. Each firing is more heatwork on the clay body and more thermal stress. Two or three glaze firings is common; beyond that the body often starts to suffer before the surface improves.

Will a refire fix crazing?

No. Crazing is a mismatch between how much the glaze and the clay contract as they cool, and refiring changes neither material. It will craze again. The fix belongs to the next pot: a different glaze or a different clay.

Do I have to add new glaze?

Not always. Pinholes sometimes heal with a second firing. Dry or rough glaze usually needs one more coat, because every load here fires the same way. If the original glaze is too thin or the wrong color, then yes, new glaze goes on.

Why does my glaze slide off a fired pot?

Because there is no porosity left to pull the water out. On bisque the pot drinks the water and the glaze grips instantly. On a fired surface it sits on top. Warming the pot to around 120 to 150 F flashes the water off and solves most of it.

Can I dip a fired pot instead of brushing?

Mostly not. Dipping relies on the pot absorbing water instantly, which a fired pot cannot do, so the glaze runs straight back off. Brushing glazes carry gums that help them grip, which is why they are the right tool here.

Will the color be the same as the new glaze?

No, and that is worth planning for. You are melting two glazes together, so the result is usually darker and more complex than the new glaze alone. Many people end up preferring it, but do not expect the swatch.

Is a refired pot still food safe?

It depends on the glazes, pot by pot. Two layers melted together are not covered by either glaze's rating on its own, and a pot that is blistered, bare in patches or crazed is not one to eat from. Check each glaze in the Food Safe Lookup, and ask us if you are unsure.

One last thing

The kiln is not the last word

Opening a kiln to a pot that did not work is one of the genuinely deflating experiences in this craft, partly because it arrives weeks after the making, when you have already decided how you feel about the piece.

Knowing that a second firing is available changes that. Not because everything can be saved, but because the verdict stops being final. Warm the pot, keep the coats light, leave room at the foot, and accept that some of them will come back worse. The ones that come back better are usually more interesting than what you originally had in mind.

Refiring works. Warm the pot, light coats, wide margin at the foot, same cone. Crazing, cracks and warping are not fixable, and two glaze layers run more easily than one.

If you want the full triage list, the sticking techniques and the six ways it goes wrong, switch to the Comprehensive Version at the top of the page.