Firing Issues

🧨 Cracking usually happens from thermal shock — when parts of the piece cool faster than others during the kiln cycle. Flat items like platters are especially at risk.

🔍 Possible causes:

• Uneven cooling

• Firing or cooling too quickly

• Pre-existing hairline cracks

• Poor kiln placement
  
  

🛠 Tips to prevent:

• Place large pieces in the center of the kiln

• Use the right-sized stilts

• Allow a slow cooling period (7–8 hrs total firing time)

• Don’t dry-foot functional items
  
  

❌ Cracked pieces cannot be repaired, but future ones can be protected with proper firing setup.

Crawling is a glaze defect where the glaze pulls away from parts of the pottery surface during firing, leaving exposed patches of bare bisque or clay. It often looks like bald spots or areas where the glaze “ran away” or “beaded up.”

👩‍🏫 Why does crawling happen?

• Dust, oil, or fingerprints on the bisque before glazing

• Too thick or uneven glaze application

• Using incompatible glaze and clay bodies

• Poor glaze adhesion (e.g., surface wasn’t clean or dry enough)

• Underfired bisque that didn’t absorb glaze properly
  
  

🛠 How to prevent it:

• Wipe bisque with a so-damp-it's-almost-dry sponge before glazing

• Apply glaze evenly—not too thick

• Let glaze dry fully between coats

• Avoid touching glazed surfaces with bare hands
  
  

🛠 How to Fix It:

Unfortunately, once a piece has crawled during firing, you can’t just reglaze and refire in most cases — especially with low-fire bisque, because the glaze won’t bond properly a second time. But here are your main options:

🧽 Option 1: Surface Touch-Ups (Only Sometimes Viable)

• If the crawling is minor, sometimes a second thin coat of glaze in the bare spots, followed by refiring, may work.

• This has the highest success rate on high-fire stoneware but we have great success with low-fire pieces as well.
  
  TIP: dremmel the edges of the crawled area down before re-glazing in order to give you an even surface area.
  
  

🔁 Option 2: Re-make the piece

• If option 1 isn't working, then we can try repainting and refiring a new bisque piece — especially if the glaze defect is large or on a visible/functional area. Often we'll  offer the guest a 20% off card to try again or  to let us remake it  at no cost to them.
  
  

🧼 Option 3: Prevent it next time

• Clean all bisque with a so-damp-it's-almost-dry sponge

• Avoid handling the surface after cleaning

• Apply glaze evenly and let each coat dry fully

Crazing refers to a network of fine cracks that appear in the glaze surface of a ceramic piece after firing. These cracks are typically not structural — they don’t go through the clay body — but they do affect the finish and can make a piece non-food-safe if severe.

🧪 Why does crazing happen?

Crazing is caused by tension between the glaze and the clay body during cooling. When they shrink at different rates, the glaze can’t keep up and starts to crack.

Common causes:

• The glaze and clay are not a good thermal match

• The piece cooled too quickly

• Over-firing or multiple firings

• Moisture absorption or thermal shock
  
  

✅ Preventing Crazing:

• Use compatible clay + glaze combos

• Fire to proper temperature

• Avoid sudden temperature changes

• Make sure the bisque is fully mature before glazing
  
  

⚠️ Is crazing bad?

• For decorative pieces: not a big deal

• For functional/food-safe ware: yes — bacteria and moisture can enter the cracks

• In some styles (like raku or crackle glazes), it’s even intentional!

🔥 What Happens When Pieces Fuse in the Kiln?

When pottery fuses in the kiln, it means that two glazed surfaces touched during firing and melted together, becoming permanently stuck. This is usually accidental and causes damage to both pieces — or even to kiln shelves.

⚠️ Causes of Fusing:

• Glazed items placed too close or touching

• Drips of glaze on the bottom of a piece

• Over-glazing or runny glaze

• Pieces stacked too soon or unevenly
  
  

💔 What Can Happen:

• The pieces become permanently stuck together

• Trying to separate them may break one or both

• Glaze can damage kiln shelves, requiring costly repairs or grinding

• Can delay customer orders and reduce usable stock
  
  
  

🛠 How to Fix It:
Fused pieces often cannot be fixed but you can try using a wooden mallet to gently tap pieces and see if they come apart. If so, a little glaze touch up and re-firing will make them as good as new!

Milky/hazy lines where layers of glaze (usually clear) overlap. Generally they happen when our clear glaze is too thick, we've overlapped the clear glaze too much during dipping, or we dipped a piece for a little too long in the glaze tank.

Cloudy spots can also happen as a result of too thick clear glaze on top of dark blues, purples, and black; it's important to verify the viscosity before dipping!

There's not much we can do, but you can try adding an extra layer of paint and re-fire!

Orange peeling is a glaze defect where the surface of the glaze ends up looking like the dimpled skin of an orange — bumpy, textured, and uneven. It’s sometimes called glaze pitting or glaze mottling.

🧪 What causes orange peeling?

It usually happens when the glaze:

• Doesn’t melt smoothly during firing

• Dries too quickly before firing

• Was applied too thick or too thin

• Has poor glaze/clay compatibility

• Contains volatile materials or bubbles that pop and freeze mid-fire
  
  

🧼 Prevention Tips:

• Mix glaze thoroughly and let it settle before applying

• Apply glaze evenly and at the right thickness

• Avoid dusty or overly porous bisque

• Fire slowly and give the kiln a soak at peak temp to help the glaze flow and smooth out

🛠 Can You Fix Orange Peeling in Pottery?

✅ Option 1: Reglaze and Refire (most common fix)

• Lightly sand or buff the bumpy areas

• Apply a fresh, even coat of glaze

• Refire — ideally with a soak/hold at peak temperature to let the glaze level out
  
  

This works best if:

• The piece isn’t crazed or cracked

• The glaze defect isn’t too thick or bubbly

⚠️ Option 2: Accept as decorative

• If the texture isn’t too rough or is visually interesting, it can sometimes be left as-is

• Not ideal for functional or food-safe ware
  
  

❌ Option 3: Repaint and refire new bisque

• If the glaze is extremely pitted or won’t accept another layer cleanly, starting fresh is best

Pinholing is a glaze defect where tiny holes or craters appear in the surface of the glaze after firing. They can be scattered across the piece or clustered in certain areas, and they’re often small but deep, exposing the clay underneath.

🧪 What causes pinholing?

Pinholing is usually caused by gases escaping from the clay body during firing and not escaping fast enough before the glaze hardens.

Common causes:

• Dust, oils, or dirty bisque

• Firing too fast, especially early on

• Underfired bisque that’s still releasing gases

• Clay that hasn’t been smoothed or burnished well

• Glaze applied too thin or unevenly
  
  

✅ How to prevent it:

• Sponge bisque pieces before glazing

• Fire bisque to the proper temperature

• Apply glaze evenly

• Slow down the early part of your glaze firing

• Try a soak - or hold - at peak temperature to let the glaze "heal"

🛠 Can You Fix Pinholing in Pottery?

Sometimes! It depends on how severe the pinholing is and where it occurs.

🎨 Option 1: Reglazing and Refiring (if piece is still functional)

• Lightly sand or clean the surface

• Apply a fresh coat of glaze over the affected area

• Refire slowly with a soak/hold at peak temperature to allow glaze to melt and flow

✅ Best for: decorative pieces or surfaces not in contact with food

⚠️ Option 2: Touch-up with cold finish or use as-is

• For non-functional art, you might fill pinholes with enamel or cold-finish products

• Sometimes, the piece is still usable if the pinholes are minor and not on food-contact surfaces

❌ Option 3: Repaint and refire a new piece

• If the pinholing is extensive or deep, especially on functional ware, it’s often better to start fresh
  
  

When the glaze shrinks more than the clay during cooling, or there's a general misfit between the glaze and clay body -- that's shivering. Usually caused by over-glazing the rim or using incompatible bisque. Flag the piece for review with a manager.

Shivering can't be resolved. Our best bet is to color match the glaze with acrylic, seal with clear sealant, and let the customer know that

"there was a manufacturing issue that neither of us could have predicted -- it's kind of like winning the reverse lottery. We've gone ahead and touched the piece up with acrylic paints so you can still use it for decorative purposes and we're issuing you a credit of equal value to give us a shot another time".

Don't forget to issues the credit by logging it on Studio Standard.

Underfired pottery refers to ceramics that were not heated to a high enough temperature during the bisque or glaze firing. This means the clay and/or glaze didn’t fully mature, causing problems in strength, finish, or food safety.

❗Signs a Piece Was Underfired:

• The piece feels chalky, soft, or dusty

• Glaze is dull, milky, or uneven

• Colors don’t look right or appear faded

• The piece might absorb water when it shouldn’t

• Sound is “dull” when tapped (vs. a clear ring)
  
  

⚠️ Why It Matters:

• Underfired clay can be weak or brittle

• It’s not food-safe — porous pieces can trap bacteria and moisture

• Glazes may not bond correctly, leading to issues like peeling or crawling
  
  

🔸 Hard spots are areas of bisque where glaze doesn’t stick properly. Yellow spots may show up from poor kiln ventilation or when pieces are too close together and glaze impurities “flash” onto each other.

🧪 Causes:

• Clay packed too tightly during pouring. If the slip hits the same spot during the greenware pouring process, it can sometimes concentrate and pack the clay in a certain area thus creating a "hard spot".

• Pieces too close together in the kiln

• Debris or residue on bisque surface

🛠 Fix:
While you can’t remove hard spots, you might be able to camouflage them with a little color touch-up and refire.
To prevent them:

• Use trusted bisque suppliers

• Keep 1"–2" spacing between pieces in the kiln