What is the difference between Stoneware and Porcelain?
Wondering what really makes porcelain so different from stoneware, and why? Why does porcelain have a reputation for being so hard to work? Let's talk about it!
Note: if you'd prefer to watch a video than read about it, skip to the bottom of this page!
Okay, so some initial differences that most people know:
- Stoneware tends to be less expensive, whereas porcelain is pricier
- Porcelain is a beautiful, pure white clay; stoneware can be many different colors
- Stoneware tends to be sandy or coarse, and porcelain is SUPER smooth
Traditionally, porcelains were only fired at Cone 8–10. However, with the magic of modern materials, we can now fire both porcelain and stoneware at Cone 5–6.
Why Stoneware Feels More Workable
There's a view among potters that porcelain is super advanced, and stoneware is easier to work with. But why do people feel that way? And what can we learn from it?
A huge reason that potters prefer stoneware is that it feels more workable than porcelain.
There are a few reasons it feels this way, but let's start with plasticity.
Plasticity measures how easily a clay body changes shape when force is applied.
Short clay bodies
- Can feel crumbly while handbuilding.
- When bending your clay, short clay bodies can form cracks
Plastic clay bodies
- Plastic bodies feel endless, like you can push them around with no problem.
- You'll notice that plastic bodies look nice and smooth while bending.
Porcelains are generally on the shorter side, while stonewares tend to be more plastic.
Structure: Sandy vs. Smooth
Another big reason people feel like porcelain can be tricky to work with is its structure.
Stonewares tend to be sandy or groggy, but porcelains are VERY smooth. There are benefits to both.
Coarse stoneware clay bodies have lower shrinkage rates because the sand or grog remains the same size in the drying and firing process. Our Pipenberg Raku clay has a ton of grog, which helps it survive the thermal shock during firing.
Porcelain has higher shrinkage rates because there is no structure except the clay itself. Expect it to shrink quite a bit. This is usually the reason that porcelain warps or slumps in the kiln. The clay particles are very affected by uneven drying and handling; they don't stand as well on their own.
This is also true when throwing or building.
Stoneware retains its shape better on the wheel; you can be more aggressive. Porcelain, however, is MUCH easier to flop. It only takes gentle touches to dramatically affect the thrown form.
We LOVE grog in this house, but let's be real… coarse stoneware can leave your hands feeling pretty demolished. Porcelain, on the other hand, is like throwing butter and is much nicer to your hands.
The texture will also affect trimming. Porcelain trims very smoothly, but stoneware can have grog that leaves drag marks on your surfaces.
Let's Get Nerdy: Clay Composition
Let's talk about clay composition, starting with Kaolin.
Kaolin is a very pure form of clay. After being weathered by the earth, it becomes the clay-sized form of aluminum silicate. It is bright white and doesn’t contain impurities.
On its own, it's just a building block; you could NOT work with kaolin straight up. Porcelain contains a LOT of kaolin as its base; stoneware also contains kaolin, but not nearly as high a percentage.
The next type of clay we're talking about is Ball clay.
Ball clay is naturally occurring clay that contains all sorts of things:
- Feldspars
- Micas
- Kaolinites
- Oxides
- etc.
It's mined straight from the source, so each location produces different ball clays. No two are 100% alike even though they have similar building blocks. The "impurities" you see in ball clays are what cause the beautiful color range we see in stoneware.
These building blocks also improve workability! Ball clay is a SUPER plastic material and contributes to the plasticity of stoneware.
Porcelain contains no ball clay. (Well, except for our CKK6! CKK6 contains ball clay to improve workability while still acting and looking like porcelain. This is why it's considered a porcelaneous stoneware.)
So how does porcelain get its workability? Bentonite, a very white, very plastic clay, is added in small percentages.
A fun thing caused by porcelain's composition is that it can be thixotropic!
Thixotropic describes that non-Newtonian, oobleck-y feeling you can get while wedging.
It can feel so weird to people who aren't used to it. A block of Seattle Freeze straight out of the bag is SO hard, but after some good smacking around, it's butter soft. Boom — there you have it, thixotropic.
Making Functionalware
Now that we've played with the clay, what are we gonna make? Potters use these clays for literally anything you could imagine. But the most popular use for these is Functionalware. This is the bowl you eat cereal out of, your emotional support mug, even your favorite "blate" (you know, bowl-plate).
Functionalware has to be durable. Porcelain has amazing resistance to thermal shock and corrosion, as you see with coffee or citrus. Stoneware is literally "like stone". It can handle some bumps and falls.
Stoneware typically needs a glaze on it to protect the clay from food and drink, but porcelain doesn't really need to be glazed. This is because stoneware has higher absorption rates and porcelain has quite low absorption rates.
Absorption is just how much water a fired clay body absorbs.
Why is the absorption rate different? That has to do with vitrification.
Vitrification is when a material turns into glass or a glass-like substance.
When fired, porcelains are almost completely vitrified and can even look shiny like glass. Stonewares are usually only partially vitrified, meaning there is more room within the clay's structure for water to enter. That’s why stoneware needs to be glazed to be food safe.
But why Is The Vitrification Different?
It’s all about composition. This time we're looking at feldspar.
Feldspar is the material that flows, moves, and fuses during firing. This is what is responsible for vitrification.
When we add heat, the feldspar melts, filling in the clay structure and fusing to itself. Stonewares have some feldspar, but porcelain has a LOT. This is what causes porcelain's glassy appearance and low absorption rate, and why stonewares have higher absorption rates and don't appear glassy when fired.
Want to know another cool thing about porcelain? It's sometimes translucent?!?! Check out Seattle Freeze if you’re curious.
Neither Is Better, Just Different
Alright! Let's come up from our deep dive.
At the end of the day, porcelain requires more control and consistent technique. Stonewares tend to be more forgiving to work with, which is why they are preferred by many potters.
Neither is better or worse, though… they're just different!
Want to try working with porcelain but don’t know where to start? Check out our newest release: the Porcelain Flight. Try all four of our SPS midrange porcelains to find your favorite. Also, did anyone mention free shipping?!
Shout-out to all these amazing potters and creators who were used as sources for this post and the corresponding video. Check them out!
Porcelain VS Stoneware - WHICH IS BEST??
Earthenware, Stoneware and Porcelain - difference in composition and their respective properties.
Types of Clays (Composition, Structure, & Bonding of Clay Minerals) | GEO GIRL
How to Choose Clay for Pottery — Complete Beginner’s Guide
