Drying Your Pottery Evenly: Avoiding Cracks
One of the most disheartening moments in any potter’s early journey is pulling back a damp cloth to find a crack running through a piece you spent hours building. It happens to beginners and experienced potters alike, but it is far more common when you are still learning how clay behaves as it dries. The good news is that cracking during the drying stage is almost entirely preventable once you understand what causes it and how to control the process.
This guide covers everything a beginner hand builder needs to know about drying pottery evenly, avoiding cracks, and getting your work safely to the bisque firing stage. Whether you are working from a kitchen table in Leeds, a garden shed in Cornwall, or a community studio in Edinburgh, the same principles apply — and they are simpler than you might think.
Why Pottery Cracks During Drying
Clay shrinks as it dries. This is not a flaw in the material — it is simply what happens as water evaporates from the clay body. Most stoneware and earthenware clays shrink somewhere between 5% and 15% from wet to bone dry, depending on the clay body and its grog content. Problems arise when different parts of a single piece shrink at different rates.
Imagine a slab-built box where the base is thick and the walls are thin. The walls dry out quickly, begin to shrink, and pull against the base, which is still wet and heavy. The stress created at that junction is often enough to split the clay. This is the fundamental cause of almost every drying crack in hand-built work: uneven drying, whether that unevenness comes from thickness differences, air flow differences, or both.
Moisture also moves through clay unevenly depending on whether a surface is exposed to air or resting against another material. A pot sitting flat on a wooden board will dry from the top and sides while the base stays damp, held in place by the board beneath it. That imbalance is a reliable recipe for cracking along the base or foot of the piece.
Understanding Leather Hard, Soft Leather Hard, and Bone Dry
Knowing the stages of drying is essential if you want to control the process. Potters use specific terms to describe how dry a piece of clay is at any given point, and understanding these stages lets you know when it is safe to handle, trim, attach, or leave a piece to dry further.
- Wet clay: Freshly worked, fully plastic. Highly prone to deformation under its own weight or from handling.
- Soft leather hard: The clay has firmed slightly. It holds its shape but can still be bent or joined. Ideal for attaching handles, coils, or additional slabs using slip.
- Leather hard: The clay feels cool to the touch and has a slight sheen. It is firm enough to handle safely and trim with a knife or loop tool. Attachments can still be made carefully at this stage, but the clay is less forgiving.
- Stiff leather hard: The clay is approaching dry. It feels room temperature rather than cool. Cracking risk is higher at this stage if you attempt to alter the piece.
- Bone dry: All water has evaporated. The clay is fragile, chalky in appearance, and ready for bisque firing. Do not attempt to join or alter it at this stage.
Moving a piece through these stages too quickly — especially in warm, dry environments or near a radiator — is the most common mistake beginners make. Slowing the process down gives the entire piece time to equalise, shrinking at the same rate throughout.
Controlling Drying Speed: Practical Methods
The simplest and most effective tool for controlling drying speed is plastic sheeting. A loose tent of thin polythene over your work traps moisture in the air around the piece, slowing evaporation. You do not want the plastic touching the clay directly, as this can cause condensation to pool in certain areas and create uneven moisture again.
In the UK, polythene sheeting is widely available from hardware shops such as Screwfix or Wickes, and many pottery suppliers sell purpose-made plastic storage bags or tents specifically for studio use. Valentines Clays in Stoke-on-Trent, Scarva Pottery Supplies in Northern Ireland, and Bath Potters’ Supplies are all reputable UK suppliers worth bookmarking, and all offer materials and accessories suited to hand builders working at home or in small studios.
Here are the core methods for controlling drying speed, in order of how much control they give you:
- Full plastic cover: Drape polythene loosely over the entire piece. This is the slowest drying option and best for large, complex, or thick-walled work that needs several days or even weeks to dry safely.
- Partial plastic cover: Leave thinner or more exposed areas uncovered while covering thicker sections. Useful when you need different parts of a piece to catch up with each other.
- Damp cloth plus plastic: Wrap a lightly damp cloth around specific thick areas — the base of a coil pot, for example — and then cover with plastic. This actively adds moisture to slow sections down.
- Open air drying: Remove the plastic entirely and allow the piece to dry at room temperature. Best suited to thin, even-walled work once it has reached a firm leather-hard state.
- Gentle heat: In cool, damp UK conditions (particularly in winter), a very gentle heat source can help move bone-dry work through the final stage. However, this must only be used on work that is already evenly leather hard or beyond, and should never be rushed with a direct heat source.
The Drying Surface Makes a Difference
What your pottery sits on during drying matters considerably. Wooden boards are popular in studios because they absorb a small amount of moisture from the base of the pot, which can actually help even out the drying. However, if the board is very dry or very absorbent, it can pull moisture from the base too quickly. Conversely, a non-porous surface like glass or tile will trap moisture underneath the piece entirely.
A useful trick is to use a piece of coarse canvas or open-weave fabric between the clay and the board. This allows air to reach the base of the piece without letting it dry too fast. Some potters use newspaper in a similar way, though newspaper can stick to very wet clay and tear when you try to remove it.
For larger flat work like tiles or slab-built trays, placing the piece between two boards — with light, even pressure applied by the top board — helps keep the piece flat while it dries and prevents warping, which is closely related to the same uneven drying forces that cause cracking.
Thickness: Getting It Consistent
No amount of careful drying technique will fully compensate for a piece built with wildly inconsistent wall thickness. If the base of your hand-built bowl is 1.5 cm thick and the walls are 5 mm, you have a significant mismatch that will make even drying genuinely difficult to achieve.
Aim for consistent wall thickness throughout your work. Most hand builders target somewhere between 6 mm and 10 mm depending on the scale of the piece. Thickness guides — small notched tools that tell you when your slab is at the right depth — are inexpensive and widely available from UK suppliers. Alternatively, two wooden dowels of the same diameter placed on either side of your clay and used as rolling guides serve the same purpose.
Pay particular attention to junctions: where handles meet walls, where a base meets a coil-built side, where a lid seat is formed. These are the points where clay tends to be thicker or where two different pieces of clay join. Blending and compressing these areas thoroughly, and then checking that the thickness is as even as possible around the join, significantly reduces the risk of cracking at those points during drying.
Attachments and Joins: Special Considerations
Attaching two pieces of clay that are at different stages of drying is one of the most reliable ways to cause a crack. If you attach a handle that you just made (soft and wet) to a mug body that is already leather hard, the handle will shrink considerably more than the body as it dries, pulling away from the join or cracking along it.
The rule is straightforward: match the dryness of all the pieces you are joining as closely as possible. If your mug body is at soft leather hard, bring your handle to the same stage before attaching it. Score both surfaces, apply a generous amount of slip (clay mixed with water to a yoghurt-like consistency, ideally made from the same clay body you are using), press firmly, and blend the join thoroughly on both sides.
After attaching, slow the drying right down. Cover the joined area loosely with plastic and allow the whole piece to dry slowly and evenly from that point. Checking joins after 24 hours and pressing any lifting edges back down gently can save pieces that might otherwise crack along the seam.
