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Whether you're just getting your hands muddy for the first time or you're firmly down the clay rabbit hole, clay terminology can sometimes feel like its own secret language.
Words like grog, vitrified, and leather hard get tossed around like everyone’s supposed to know what they mean. And to be fair, we often forget that others don’t know what they mean because they’ve been part of our world for decades. But the reality is many of us had to learn these on the fly when we first began our own clay journey.
We want you to have the easiest start so we’ve compiled this mini glossary of clay terms that we use most often in our ceramic clay studio. These are terms that you’ll hear in our workshops, blog posts, and captions. No gatekeeping, no jargon. Just clear, friendly explanations so you can focus on creating!
Clay Body: the actual clay. This is a specific blend of clays, minerals, and additives mixed together to create a clay with certain working and firing properties.
Think of it like a recipe. Some are soft and smooth, others are gritty and strong. Some are great for throwing on a wheel, others shine in hand-building. The "body" part just means the full makeup of the clay you're using, not just the raw material. For more insight into our favorite clays and what we use them for, check out our "clay bodies" blog.
Stages of Clay (From Wet to Fired)
Wet Clay: Super flexible, mold-able, and ready to shape. It feels smooth and cool to the touch. Can vary from feeling like very soft cream cheese (porcelain) to an almost tough or sandy body, depending on the clay. Sometimes in a more formal academic setting it can be referred to as “plastic” but most often we say wet, fresh, or raw clay.
Leather Hard: This refers to when clay is partially dried, but still carvable. It holds its shape but has some give like firm cheese. This stage is ideal for trimming, adding handles, or refining details. We often wait until our pieces are at this stage before smoothing with a damp sponge.
Bone Dry: Fully dried and incredibly fragile. The clay feels chalky and cold. It's brittle and will break easily so handle it with care! Once clay is bone dry, it’s ready to be bisque fired. .
Bisque Fired(First Firing): The clay has been fired once at a lower temperature to harden it, but it’s still porous. At this stage the clay is strong and absorbent enough to apply glaze. The clay feels more like ceramic, but it's still absorbent, chalky, and unfinished. You can still paint, wax, or glaze it before firing again.
Glaze Fired / Vitrified (Final Stage):
The second firing, and the one that brings all the magic. This firing melts the glaze, adhering it to the cay body, finishes the piece, and gives it its final finish (glossy, matte, smooth) . If the clay body reaches “vitrification”, it becomes water-tight and dense. The piece is now fully ceramic. Durable, beautiful, and ready to use.
Glazes
Underglaze: a type of ceramic colorant, kind of like paint for clay. It goes on before any glaze, and it doesn’t melt or move much in the kiln, so your designs stay crisp. You can use underglaze on wet, leather-hard, or bisqued clay, depending on your project.
In our workshops, we have folks apply underglaze directly onto their freshly made, still-wet pieces. This allows for more expressive, in-the-moment decorating while the clay is still in the greenware stage. After the pieces dry, we bisque fire them, then apply a clear glaze on top, and then fire them again. This helps seal in the design and makes the piece food-safe and finished.
Pro tip: “Stroke & Coat” is forgiving, vibrant, and easy to use. Perfect for beginners and kids!
Clear glaze: a transparent coating applied over underglaze or bare clay to seal the surface and give it a finished look. It can be glossy or matte, but in both cases, it helps protect your design while making the piece food-safe and watertight.
At our studio, we use a zinc-free, food-safe clear glaze for all workshop projects. It’s applied after the first (bisque) firing to preserve the vibrancy of underglazes and ensure a smooth, even finish during the final firing.
Why zinc-free? Some underglazes don’t react well with zinc in clear glazes. It can cause cloudiness or weird color changes. Ours stays clear and true!
Studio Vocabulary:
Score and Slip (a.ka. Scratch and Attach): This is refers to the process of joining two pieces of clay. You scratch up the surfaces you want to stick together (called scoring), add some slip (clay + water mixture), and then press them firmly together. It's like glue for clay. It's also an important step and prevents your handle or coils from "popping" in the kiln.
Slip: is clay mixed with water until it becomes a smooth, creamy paste. It’s used like glue to join two pieces of clay together. It's especially important when you’re attaching handles, coils, or decorative elements.
Bonus: Some potters also use colored slip for decoration by painting or trailing it onto surfaces before firing
Grog: is pre-fired clay that’s been crushed into tiny gritty particles and added back into a clay body. It gives clay more strength, reduces shrinkage, and helps prevent cracking during drying or firing.
You’ll feel the difference: clay with grog has a sandy texture and holds shape well, which makes it ideal for handbuilding, large forms, and anything where structure matters.
Slab: A slab is a flat, even sheet of clay, kind of like rolling out cookie dough. You can cut it into shapes, form it into walls, or use it as a base for handbuilt projects.
Types of Ceramic Construction
Slab-built/ Slab Construction: This refers to pottery made by assembling slabs of clay. Think of it like building a box, cup, or sculpture by cutting out pieces and joining them together. It’s a common handbuilding technique, especially for beginners or structured forms. Slab is one of our favorite forms of construction because it's incredibly accessible and requires few tools.
Press Mold: A method where you press clay into or over a form (often plaster, bisque, or wood) to create a consistent shape. It’s great for replicating forms like plates, tiles, or small objects. The mold does the shaping and you do the decorating.
Wheel-throwing: Clay shaped on a pottery wheel! The spinning motion helps center and form symmetrical shapes like bowls, mugs, and vases. It’s a skill that takes time but is super satisfying once you get the feel of it.
Handbuilding: any clay technique that doesn’t involve a wheel. This includes slab building, coil building, pinch pots, press molds. Basically anything made with your hands, tools, and creativity! This is the type of clay construction that we teach at our in-person workshops and in our online tutorials. We love it because of it's accessibility and minimal tool In fact, this is how we began our clay journey, right at our kitchen table!
This is a growing glossary and we'll add more terms as they arise.
In the meantime if you have questions or topics you'd like us to cover, send us a DM on Instagram (@carterandrosepdx)