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Working With Porcelain: Why It Isn’t Difficult—Just Different
Porcelain is often regarded as a challenging clay body to work with. Potters who attempted it often like the medium, however some give up not understanding how to handle the medium. They perceive it as fragile, finicky, and tedious. However, my challenging personality and years of experience have led me to a different perspective. Today, I advocate for working with porcelain clay. While it is demanding, the rewards and benefits make it all worthwhile.
My Early Journey With Porcelain Clay
My first experiences working with porcelain, was unsuccessful. To make it worse, more experienced potters and instructors intimidated me. In my early days of pottery I created simple forms, fired to cone 8.
Much of my early porcelain work ended up in pit firings. I created incredibly thin porcelain pieces that were fired in pits. These works eventually helped me secure permanent residency for my family and me in the United States.
Those early works evolved into sculptural pit-fired pieces that carried my emotions during a time that I was still griefing the loss of leaving my home country, South Africa.
Eventually, the heaviness lifted. I began seeing light, movement, and ballerinas in sheer dresses in my mind’s eye. Southern Ice porcelain became my medium of joy. Translucency, color, and light became symbols of the future.
Porcelain is often regarded as a challenging clay body to work with. Potters who attempted it often like the medium, however some give up not understanding how to handle the medium. They perceive it as fragile, finicky, and tedious. However, my challenging personality and years of experience have led me to a different perspective. Today, I advocate for working with porcelain clay. While it is demanding, the rewards and benefits make it all worthwhile.
My Early Journey With Porcelain Clay
My first experiences working with porcelain, was unsuccessful. To make it worse, more experienced potters and instructors intimidated me. In my early days of pottery I created simple forms, fired to cone 8.
Much of my early porcelain work ended up in pit firings. I created incredibly thin porcelain pieces that were fired in pits. These works eventually helped me secure permanent residency for my family and me in the United States.
Those early works evolved into sculptural pit-fired pieces that carried my emotions during a time that I was still griefing the loss of leaving my home country, South Africa.
Eventually, the heaviness lifted. I began seeing light, movement, and ballerinas in sheer dresses in my mind’s eye. Southern Ice porcelain became my medium of joy. Translucency, color, and light became symbols of the future.
One of Antoinette Badenhorst’s exquisite sculpted porcelain bowls.
Antoinette Badenhorst’s beautiful, translucent, sculpted porcelain bowl was photographed during a workshop in Simonstown, South Africa.
Porcelain isn’t difficult. It’s different.
Unlike stoneware or earthenware, porcelain is worked as clay but becomes something closer to glass when fired.
Understanding that single truth changes everything about how you handle, design, and fire it.
Unlike stoneware or earthenware, porcelain is worked as clay but becomes something closer to glass when fired.
Understanding that single truth changes everything about how you handle, design, and fire it.
​Sometimes, certain cracks are intentionally allowed. In this case, Antoinette Badenhorst stretched the clay over the balloon while it was being made. The bowl edges cracked. She, stopped it from going too far and enhanced the crack to give the bowl an organic appearance.
Why Porcelain Cracks: Understanding the Real Causes
Cracking in porcelain isn’t random—it’s usually caused by handling, design, firing, or glazing mistakes, to name a few. Over the years, I’ve seen every kind of crack imaginable, both in my own studio and in work sent to me by students from around the world through TeachinArt.com.
Let’s break them down.
Cracking in porcelain isn’t random—it’s usually caused by handling, design, firing, or glazing mistakes, to name a few. Over the years, I’ve seen every kind of crack imaginable, both in my own studio and in work sent to me by students from around the world through TeachinArt.com.
Let’s break them down.
S-cracks are easily formed when throwing off the hump. It’s essential to ensure that the bottom of bowls thrown in this manner are compacted properly.
This crack was fixed, however because of the particle alignment, it still shows in the translucent pot.
Handling Cracks in Porcelain: What to Do and What to Avoid
Porcelain becomes extremely fragile as it dries because it contains less clay, than stoneware or earthenware.
Key rule:
Finish shaping and altering porcelain before it passes the leather hard stage.
When porcelain starts changing color as it dries, it’s too late to alter the clay without causing problems.
How to Prevent Handling Cracks
Porcelain becomes extremely fragile as it dries because it contains less clay, than stoneware or earthenware.
Key rule:
Finish shaping and altering porcelain before it passes the leather hard stage.
When porcelain starts changing color as it dries, it’s too late to alter the clay without causing problems.
How to Prevent Handling Cracks
- Trim as soon as the base and rim are evenly moist.
- Be extra careful with rims—they crack under little pressure on the wheel head.
- Handle the semi-dry porcelain carefully. Even if you are successful in fixing a crack, it may show up in translucency.
The cracks in one of Antoinette’s students’ trays were caused by weak particle alignment.
Why Porcelain Handles Crack (And How to Fix It)
Many potters struggle with porcelain handles. The real culprit in most cases is particle orientation.
Clay shrinks in unison only when its particles are aligned and compacted evenly. A handle, unconditionally of the way it is formed, has its own direction of particles, and when you attach it to a mug, it’s like two traffic flows meeting head-on.
You need an off-ramp.
How to Attach Porcelain Handles Successfully
Many potters struggle with porcelain handles. The real culprit in most cases is particle orientation.
Clay shrinks in unison only when its particles are aligned and compacted evenly. A handle, unconditionally of the way it is formed, has its own direction of particles, and when you attach it to a mug, it’s like two traffic flows meeting head-on.
You need an off-ramp.
How to Attach Porcelain Handles Successfully
- Score and wet thoroughly. (remember slip particles are diluted and in disarray!)
- Attach when both parts are equally moist
- Compress and blend the joint well
- Think about handles as foreign objects that must become unified with the form
This is a good example of particles in the handle of a mug that were not aligned with those in the mug wall.
A diagram illustrates the flow of particles when a handle is attached to a porcelain mug.
Preventing Design Cracks in Porcelain Work
Porcelain must be formed evenly. Uneven thickness leads to slumping, tearing, and cracking.
At high temperatures, porcelain becomes pyro plastic — it softens like glass.
Design Tips for Porcelain
Porcelain must be formed evenly. Uneven thickness leads to slumping, tearing, and cracking.
At high temperatures, porcelain becomes pyro plastic — it softens like glass.
Design Tips for Porcelain
- Keep walls consistent in thickness
- Avoid heavy areas attached to thin ones.
- Heavy clay will be drawn towards the kiln shelf and will drag thinner clay along with it.
The glaze applied to the bowl was too thick, causing it to break into two pieces. This is a very clear example of dunting.
The vase’s spout, too heavy for the sheet of clay it was attached to, tore and cracked open.
Firing Cracks and Dunting in Porcelain
Dunting happens when the kiln heats or cools too fast. It can occur in bisque or glaze firing.
If a piece comes out of the kiln split cleanly in two, or cracks days later with sharp, glassy edges—the cooling cycle is usually to blame.
Dunts in bisque ware is not common in porcelain clay, but glaze cracking happens often.
How to Prevent Firing Cracks
Dunting happens when the kiln heats or cools too fast. It can occur in bisque or glaze firing.
If a piece comes out of the kiln split cleanly in two, or cracks days later with sharp, glassy edges—the cooling cycle is usually to blame.
Dunts in bisque ware is not common in porcelain clay, but glaze cracking happens often.
How to Prevent Firing Cracks
- Slow down your firing and especially the cooling schedule
- Pay special attention to cooling around quartz inversion
- Don’t rush porcelain through temperature changes
Over-Glazing: A common Cause of Porcelain Cracks
Too much glaze—especially inside forms—can split porcelain apart.
If glaze pools thickly in the bottom of bowls or vessels, it creates stress during firing.
Glazing Tips for Porcelain
Too much glaze—especially inside forms—can split porcelain apart.
If glaze pools thickly in the bottom of bowls or vessels, it creates stress during firing.
Glazing Tips for Porcelain
- Apply thin, even glaze layers
- Avoid heavy pooling, especially in the interior bottom of thin pots
- Spray glazing is an effective technique for applying glaze to thin porcelain.
This beautiful crystalline plate, exposed to uneven cooling in the kiln, broke into pieces.
Spiral Cracks in Wheel-Thrown Porcelain
There’s a misconception that porcelain must be thrown fast to prevent collapse. In reality, it’s advisable to throw porcelain slowly, with a deliberate focus on compacting the clay particles. Spiral cracks occur when certain clay parts remain misaligned and shrink unevenly. These cracks mostly become visible during the final firing process.
How to Avoid Spiral Cracking
There’s a misconception that porcelain must be thrown fast to prevent collapse. In reality, it’s advisable to throw porcelain slowly, with a deliberate focus on compacting the clay particles. Spiral cracks occur when certain clay parts remain misaligned and shrink unevenly. These cracks mostly become visible during the final firing process.
How to Avoid Spiral Cracking
- Throw slowly and meticulously.
- Compression should be applied uniformly to the entire object, including its interior, exterior, and base, considering both the inside and outside.
- Don’t rush. Form your pot deliberately and carefully.
Is the lack of compression on the interior of the bowl due to insufficient compression, or could it be that the area where the wall and base meet was left wetter than the rest of the bowl?
These are typical spiral cracks that either went unnoticed during the bisque kiln firing or occurred early in the glaze fire.
The sketch depicts a bowl to the left, with clay particles that were not uniformly compressed.
General Tips to Prevent Base and Rim Cracks
- Trim thin porcelain before it gets too dry
- Attach a a sponge bat on the wheel head to trim delicate rims on
- Compact the base inside and out
- Keep wall thickness even throughout
These sketches from Antoinettes porcelain online classes illustrate the various cracks that may develop in porcelain due to uneven drying.
Tiny V-cracks have appeared on one of Antoinette’s students’ bowls. If these cracks are detected in time, they can be repaired.
This plate was subjected to uneven heating and cooling in the kiln, resulting in dunting.
Antoinette Badenhorst, a renowned potter, presents online classes and hands-on workshops worldwide. In 2014, she and her husband, Koos, founded TeachingArt Online School of Art. Together with other experienced and renown teachers, they provide comprehensive online courses for potters and artists globally. These comprehensive learning experiences are meticulously designed to enhance skills, boost confidence, and foster a deeper understanding of pottery, rather than offering mere demonstrations.
This little cup was made by one of Antoinettes students. It looks like the crack was formed during firing. The glaze curls into the crack, therefore this is not dunting from the glaze firing.
The sketch from Antoinettes online classes with TeachinArt illustrates a V-crack that forms when the rim dries more quickly than the base.
This crack is most possibly due to glaze that was too thick for the body.
This crack is related to s-cracks and due to uneven drying.
This crack likely occurred because the base was drying on a non-absorbing bat. Alternatively, it may not have been cut loose from the bat after it was thrown.
If you enjoyed and gained something from this blog post, please share it with your friends. Unfortunately, I won’t be traveling abroad this year because I need to catch up on my studio work and am also writing a book.
Details of my next porcelain workshop is available on the Workshop page
Details of my next porcelain workshop is available on the Workshop page
TAGS
porcelain clay, working with porcelain, porcelain pottery, porcelain cracking, porcelain firing, porcelain handles, wheel thrown porcelain, translucent porcelain, porcelain glazing, how to prevent cracks in porcelain
porcelain clay, working with porcelain, porcelain pottery, porcelain cracking, porcelain firing, porcelain handles, wheel thrown porcelain, translucent porcelain, porcelain glazing, how to prevent cracks in porcelain
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Working with porcelain clay may scare you in the beginning but once you've learned how porcelain differs from other clay mediums, you will be hooked and really enjoy to work with it.
A note from Antoinette:
During those early days of presenting workshops globally, my English language skills were still developing. Although I still occasionally struggle to find my words in English, my proficiency has improved significantly, which I am very grateful for. Growing up and even as a young adult, despite being exposed to English, Afrikaans was our main language.
During those early days of presenting workshops globally, my English language skills were still developing. Although I still occasionally struggle to find my words in English, my proficiency has improved significantly, which I am very grateful for. Growing up and even as a young adult, despite being exposed to English, Afrikaans was our main language.
Hand building porcelain can be as easy or as intricate as a potter wants to do it. Antoinette likes to use translucency in her sculpted porcelain bowls. She use any clay technique to create her ceramic art.
Antoinette shares some of her porcelain secrets in this behind-the-scenes look at one of her first porcelain workshops in Canada. She shows how you can take a leather-hard porcelain bowl and safely bring it back to a soft, workable state—then reshape or sculpt it into a beautiful new form.
You’ll see how she creates a press mold and turns it into a bowl, while explaining why it’s important for potters to truly understand porcelain as a material and build a relationship with it.
Antoinette likes to call porcelain a “diva” 😄 because it has its own personality and needs to be handled with care. She even touches on the history of porcelain to help explain its unique characteristics.
The video features highlights from her hands-on workshop, where she teaches both handbuilding and wheel-throwing techniques. Since that first workshop, Antoinette has gone on to teach porcelain classes around the world
You’ll see how she creates a press mold and turns it into a bowl, while explaining why it’s important for potters to truly understand porcelain as a material and build a relationship with it.
Antoinette likes to call porcelain a “diva” 😄 because it has its own personality and needs to be handled with care. She even touches on the history of porcelain to help explain its unique characteristics.
The video features highlights from her hands-on workshop, where she teaches both handbuilding and wheel-throwing techniques. Since that first workshop, Antoinette has gone on to teach porcelain classes around the world
Orange press molded porcelain bowl, envelope formed on a wheel thrown pedestal.
Chartreuse green press molded porcelain bowl, envelope formed on a wheel thrown pedestal.
Antoinette's porcelain classes whether it is online or hands-on is loaded with explanations and tips and is suitable for beginner to advanced potters. She provides a variety of porcelain tips and compare them with regular pottery techniques. Her workshops are normally a mix between wheel throwing and hand building techniques. See Antoinettes Ceramic Workshops
Tags:
#PorcelainSecrets, #WorkingWithPorcelain, #PorcelainClay, #CeramicTechniques, #PotteryTips, #HandbuildingCeramics, #WheelThrowing, #PorcelainWorkshop, #CeramicArtist, #PorcelainByAntoinette, #AntoinetteBadenhorst, #StudioPottery, #ClayLife, #CeramicsEducation
#PorcelainSecrets, #WorkingWithPorcelain, #PorcelainClay, #CeramicTechniques, #PotteryTips, #HandbuildingCeramics, #WheelThrowing, #PorcelainWorkshop, #CeramicArtist, #PorcelainByAntoinette, #AntoinetteBadenhorst, #StudioPottery, #ClayLife, #CeramicsEducation
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There are many myths about porcelain. This started already in the 12th century when Marco Polo discovered potters in China working with T'zu, the name originally used by these potters. In the 17th century, John Böttger began to understand the make-up of porcelain, and this is where our story starts.
Porcelain needs to be wedged properly to obtain a homogeneous water consistency.
Coning the clay on the pottery wheel helps to center the clay well.
The Understanding Porcelain online class explores the character of porcelain, and Antoinette explains how the materials used in those early ages of the discovery of porcelain are still the same materials used today, why it saturates with water so quickly, and why it dries faster than other clay bodies.
Now, in the 21st century, we have much more knowledge about and many more resources to choose from as far as raw materials are concerned than was originally available in the City of Tinqui. It is also possible that potters can have a much clearer understanding of what we are dealing with in porcelain.
Now, in the 21st century, we have much more knowledge about and many more resources to choose from as far as raw materials are concerned than was originally available in the City of Tinqui. It is also possible that potters can have a much clearer understanding of what we are dealing with in porcelain.
Porcelain online classes
During the 10 weeks that Antoinette presents her "Understanding Porcelain" online class, students can expect clear, close-up, and detailed videos that they can review and ask questions about as often as they need to. Antoinette teaches and demonstrates everything that any potter needs to understand about porcelain. Whether hand building, throwing, trimming, or altering on the potter’s wheel, beginners to advanced potters will learn to work easily and successfully with the “Diva of clay”. Antoinette addresses design. Porcelain is a semi-glass, which is the main reason why porcelain slump, warp, and crack. Firing and glazing techniques help to prevent mistakes and ensure success.
If the clay is well centered the final centering happens right in the middle interior bottom after the clay is opened.
2 silicone kidneys help to remove any unevenness, thin the clay and remove wet slip from the clay walls.
What to expect from the Class contents.
The class is divided into weeks, which potters can follow or ignore. These are logical breaks between the videos and are intended to give potters an opportunity to pause and practice what they've learned. Potters can review 6 weeks of class content ( a 5-day hands-on class converted to 6 weeks online) over a 10-week period. They can review the content as often as they need to, and they can discuss questions and gain assistance from Antoinette during this time. Potters watch the videos at their own time. There are more than 30 videos to work through, on average 7-15 minutes long. When the classes are over, the PDFs are available to download as handouts.
In week 1, the class is designed to make a transition from stoneware or earthenware clay to porcelain. There are clear and specific differences in the approach between these clay mediums. The introduction, which includes some porcelain history and the origin of clay, prepares you for that.
In week 1, the class is designed to make a transition from stoneware or earthenware clay to porcelain. There are clear and specific differences in the approach between these clay mediums. The introduction, which includes some porcelain history and the origin of clay, prepares you for that.
Pinch the clay inside a hollow area like the palm of the hand. this will help to keep the walls even. The form of the bowl can be obtained later.
Once the walls are even, the form can be changed and additions can be added to the bowl.
During Week 2, potters get to know and control porcelain with a pinching technique. This allows potters to understand the drying stages of porcelain clay. Porcelain clay, just like stoneware clay, comes in different kinds. Apart from different firing temperatures, porcelain clays are designed to either be thrown on the wheel, hand-built, or slipcast. In the end, potters choose a porcelain for their specific needs. If you are unsure of which kind to choose, you can contact Antoinette.
Week 3 is a week of throwing porcelain on the pottery wheel. Beginners, intermediate, and advanced potters learn to push the limits on the wheel to throw thin, evenly, and translucent porcelain bowls and cylinders. The preparation of the clay is crucial, and the techniques include throwing with 2 kidneys, a great way to compress the clay and create even walls, a crucial element of success with porcelain.
Week 3 is a week of throwing porcelain on the pottery wheel. Beginners, intermediate, and advanced potters learn to push the limits on the wheel to throw thin, evenly, and translucent porcelain bowls and cylinders. The preparation of the clay is crucial, and the techniques include throwing with 2 kidneys, a great way to compress the clay and create even walls, a crucial element of success with porcelain.
Trimming a bowl right side up while it is still attached to the wheel, allows a potter to keep the walls even.
It is possible to expand or change the foot rim after it is trimmed.
The right tools and the right drying stages will help potters during trimming of the pots. The final outcome of transparent porcelain is exciting, but to do it successfully requires knowledge. Potters learn how to trim smoothly and to eliminate unplanned marks that can show up in the translucency of the walls. Even walls prevent slumping and cracking of the rims. During week 4, potters learn all about trimming and how to ensure the forms turn out successfully.
One of the myths out there is that porcelain is a difficult medium. Fact is, porcelain is the "Diva of Clay" that demands attention to detail. During this class, the whole course begins to fall into place, and students get to understand why it is needed to do things in a specific way.
However, one of the big takeaways is that there is no right or wrong way; only one that is comfortable and one that works.
One of the myths out there is that porcelain is a difficult medium. Fact is, porcelain is the "Diva of Clay" that demands attention to detail. During this class, the whole course begins to fall into place, and students get to understand why it is needed to do things in a specific way.
However, one of the big takeaways is that there is no right or wrong way; only one that is comfortable and one that works.
By controlling the moisture content of a porcelain bowl, it is possible to alter the form completely.
a wheel thrown porcelain bowl, trimmed, altered and carved, ready to dry out.
TeachingArt is among others, a Ceramic School where potters learn why certain things are done the way they are done. It is more than just demonstrations, but an in-depth study that is suitable to teach in college. The beautiful thing is that once potters understand, they can change the rules to suit their specific needs, and Antoinette is there to walk those ideas through and assist them. During week 5, potters learn to alter their porcelain vessels, taking design into consideration, and during week 6, the glazing and firing of porcelain are the final actions to ensure success with porcelain. With the right approaches, it becomes easy to obtain beautiful porcelain objects.
Antoinette shares a variety of clay techniques during her online and hands-on classes. The techniques that she uses are specialized, and she helps her students to develop their own techniques. Once a student of Antoinette, always one of her students. She is willing to work with you as long as you need it.
Antoinette shares a variety of clay techniques during her online and hands-on classes. The techniques that she uses are specialized, and she helps her students to develop their own techniques. Once a student of Antoinette, always one of her students. She is willing to work with you as long as you need it.
Wheel thrown translucent green porcelain bowl. The piece is in the permanent collection of the AMOCA Museum of Art in California.
Hand-built translucent porcelain bowl on a pedestal. The bowl is altered and carved and donated many years ago to CERF, the Craft Emergency Relief Fund.
Unfortunately, the videos are not available permanently, since TeachinArt.com treat their online classes like hands-on workshops.
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Porcelain has long had the reputation of being a difficult clay body to work with. Much of this reputation comes not from forming the clay, but from understanding the firing process. Porcelain responds very specifically to heat and temperature, kiln design, glaze fit, and especially to the way it cools after firing.
By understanding the relationship between raw materials, firing temperature, and cooling cycles, potters can make informed decisions about kilns, clay bodies, and firing schedules that lead to strong and reliable porcelain work.
Now that we have to established the concept of porcelain and the distinctions between high-firing and low-firing types, and how to determine the appropriate kiln for your studio needs.
By understanding the relationship between raw materials, firing temperature, and cooling cycles, potters can make informed decisions about kilns, clay bodies, and firing schedules that lead to strong and reliable porcelain work.
Now that we have to established the concept of porcelain and the distinctions between high-firing and low-firing types, and how to determine the appropriate kiln for your studio needs.
The Tradition of High-Firing
David is one of the instructors at Teachinart. See his profile here: Click on the image to go to his profile.
If you are a "purist" who believes only in high-fired porcelain, you may find yourself drawn to wood firing. This was the original process used when porcelain was a secret known only to the Chinese. Wood firing offers a unique interaction between fly ash and the clay body that modern kilns struggle to replicate.
However, if your goal is a reliable studio experience with the authentic appearance of porcelain, any firing range from Cone 6 to Cone 10 should suffice.
However, if your goal is a reliable studio experience with the authentic appearance of porcelain, any firing range from Cone 6 to Cone 10 should suffice.
Low-temperature porcelain requires a carefully balanced recipe. A helpful analogy is a cake that appears golden brown on the outside while still raw inside. The surface may look finished, but internally the material has not fully matured.
To achieve translucency at lower temperatures, the clay body often needs more glass-forming materials and less clay. While this promotes vitrification, it also reduces the plasticity of the clay body, making it more difficult to work with.
Plasticizers such as bentonite, Macaloid, or Veegum T may be added to enhance workability. However, these materials introduce additional variables, including changes in drying behavior and shrinkage and thixotropy of the clay.
Historically, soft-paste porcelain was developed in Europe as an attempt to imitate Chinese porcelain before the true formula for hard-paste porcelain was understood. Although beautiful, soft-paste porcelain is generally weaker than traditional high-fired porcelain.
To achieve translucency at lower temperatures, the clay body often needs more glass-forming materials and less clay. While this promotes vitrification, it also reduces the plasticity of the clay body, making it more difficult to work with.
Plasticizers such as bentonite, Macaloid, or Veegum T may be added to enhance workability. However, these materials introduce additional variables, including changes in drying behavior and shrinkage and thixotropy of the clay.
Historically, soft-paste porcelain was developed in Europe as an attempt to imitate Chinese porcelain before the true formula for hard-paste porcelain was understood. Although beautiful, soft-paste porcelain is generally weaker than traditional high-fired porcelain.
Wood fired translucent porcelain bowl by David Voorhees
Translucent sculpted porcelain bowl by Antoinette Badenhorst
The Limits of Electric Kilns
Functional porcelain objects by Antoinette Badenhorst.
Beyond these temperatures, the technical challenges mount.
Firing exceeding 1285°C (2345°F) requires stable fluxes to work with refractory silica and kaolin, melting the clay into glass while maintaining its form.
To my knowledge, standard electric pottery kilns rarely reach temperatures higher than Cone 12–14 (1360°C).
If you are aware of a manufacturer producing electric kilns capable of exceeding Cone 14, please share that information in the comments!
Firing exceeding 1285°C (2345°F) requires stable fluxes to work with refractory silica and kaolin, melting the clay into glass while maintaining its form.
To my knowledge, standard electric pottery kilns rarely reach temperatures higher than Cone 12–14 (1360°C).
If you are aware of a manufacturer producing electric kilns capable of exceeding Cone 14, please share that information in the comments!
The Science of Low-Fire Porcelain
Firing below 1220°C (2228°F) is possible in almost any kiln, but the chemistry changes. At lower temperatures, we must use frits—expensive, factory-produced fluxes.
The challenge here is that silica and kaolin are highly refractory (resistant to melting). If the heating isn't perfectly even, you end up with excess free quartz, which weakens the ceramic because insufficient cristobalite forms.
The Cake Analogy: Low-firing porcelain is like a cake baked golden brown on the outside but raw in the middle. It requires a delicate balance of raw materials, making the recipe "fussy" and prone to failure if mining sources change.
To achieve translucency at low temperatures, you need more glass-forming materials and less clay. This makes the clay less pliable. While plasticizers like Bentonite or VeeGum T can help workability, they introduce their own set of complications.
The challenge here is that silica and kaolin are highly refractory (resistant to melting). If the heating isn't perfectly even, you end up with excess free quartz, which weakens the ceramic because insufficient cristobalite forms.
The Cake Analogy: Low-firing porcelain is like a cake baked golden brown on the outside but raw in the middle. It requires a delicate balance of raw materials, making the recipe "fussy" and prone to failure if mining sources change.
To achieve translucency at low temperatures, you need more glass-forming materials and less clay. This makes the clay less pliable. While plasticizers like Bentonite or VeeGum T can help workability, they introduce their own set of complications.
Low fired Porcelain by Bryan Hopkins.
Porcelain cup with crazed glaze.
Note the thick glaze layer in this bowl. In this case the glaze application was too thick and the bowl dunted.
Terra sigilata shiver off the clay body
Understanding the "Body-Glaze" Bond
Common Firing Defects
|
Defect |
Cause |
Appearance |
|
Crazing |
Glaze contracts faster than the clay during cooling |
A network of fine cracks in the glaze. |
|
Shivering |
Clay contracts significantly more than the glaze. |
Glaze peels off like paint chips; edges are razor-sharp. |
|
Dunting |
Cooling too fast, creating thermal shock. Too much glaze in comparison with the clay can also cause dunting. |
The pot cracks or breaks in two (sometimes weeks later). |
Because porcelain is a dense material containing 10%+ cristobalite, it is highly sensitive during two critical cooling periods:
- 573°C (1063°F): The Quartz Inversion.
- 226°C (439°F): The Cristobalite Inversion.
Kiln controler to make sure the speed of the firing is under control.
Recommendations for Buyers:
If you fire in a community studio or a mixed kiln with stoneware, consider using saggars. These lidded containers act as a "kiln within a kiln," protecting the porcelain from drafts and slowing the cooling process naturally.
- Electronic Controllers: Highly recommended. They allow you to program a "slow cool" or "down-fire" to ensure the clay and glaze contract in concert.
- Manual Control: If you don't have a controller, close all vents (peep holes) once the kiln reaches a "yellow-orange" heat (approx. 1000°C) to prevent drafts.
- The Golden Rule: Never open the kiln above 200°C (392°F). Sudden airflow can cause a delicate piece to disintegrate instantly.
If you fire in a community studio or a mixed kiln with stoneware, consider using saggars. These lidded containers act as a "kiln within a kiln," protecting the porcelain from drafts and slowing the cooling process naturally.
Final Thoughts
Working successfully with porcelain requires understanding more than just the clay itself. Firing temperature, glaze fit, cooling cycles, and kiln design all play critical roles in the strength and durability of the finished piece.
When potters respect porcelain’s need for controlled heating and especially slow cooling, they unlock the remarkable qualities that have made porcelain one of the most admired ceramic materials in history.
When potters respect porcelain’s need for controlled heating and especially slow cooling, they unlock the remarkable qualities that have made porcelain one of the most admired ceramic materials in history.
One of the clay tests for a translucent ^6 porcelain. The flux was too powerful. Seem ore about this under clay recipes.
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High-fire porcelain, Low-fire porcelain, Electric kilns for porcelain, Kiln cooling cycle, Crazing, Shivering, Porcelain translucency. porcelain pottery, firing porcelain, porcelain kiln firing, ceramic firing temperatures, cone 10 porcelain, pottery kiln guide, porcelain glaze fit, crazing and shivering, dunting in ceramics, ^6 porcelain clay, ceramic materials science, porcelain cooling cycle, pottery kiln tips,
High-fire porcelain, Low-fire porcelain, Electric kilns for porcelain, Kiln cooling cycle, Crazing, Shivering, Porcelain translucency. porcelain pottery, firing porcelain, porcelain kiln firing, ceramic firing temperatures, cone 10 porcelain, pottery kiln guide, porcelain glaze fit, crazing and shivering, dunting in ceramics, ^6 porcelain clay, ceramic materials science, porcelain cooling cycle, pottery kiln tips,
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