Why slab building suits a rectangular candle holder

A rectangular candle holder is one of the most satisfying slab projects you can make. It teaches you to roll an even slab, measure accurately, cut clean panels and join seams that stay put. The straight sides also give you a useful place to practise supporting a form from the inside. Aim for finished dimensions around 10 cm long, 7 cm wide and 7 cm tall. Use a grogged stoneware or a smooth earthenware clay. A lightly grogged body is more forgiving when the walls are thin, while a smooth body takes a crisp finish and glaze beautifully.

Rolling an even slab

Start with clay that is soft enough to roll but not sticky. Wedge it well, then shape it into a rough rectangle. Set two wooden battens — about 8 mm thick for the walls and 10 mm for the base — on a plasterboard or canvas-covered board. Place the clay between them and roll from the centre outwards, keeping the rolling pin parallel to the battens. Rotate the slab a quarter turn after every few passes and flip it over once or twice. This stops the clay from sticking and helps you achieve an even thickness. Finish by running a rib over the surface to compress the clay and align the particles. If the slab starts to sag, leave it between two sheets of newspaper or under plastic until leather-hard. A slab that is too wet will stretch when you pick it up; too dry and the edges will crack.

Cutting precise panels

Make a paper or card template before you cut anything. For a 10 x 7 x 7 cm holder you need a base 10 x 7 cm, two side panels 10 x 7 cm, and two end panels 7 x 7 cm. Place the template on the slab and cut around it with a needle tool or fettling knife, using a metal ruler as a straight edge. Angle the blade slightly outwards so the outer face is a fraction larger than the inner; this gives you material to compress when joining. Measure twice and cut once — clay remembers every hesitant cut. Lay each panel flat and cover it with plastic; keep all pieces at the same stage of firmness or the seams will fight each other later.

Joining the seams

Score the edges of the base where the walls will sit. Score the bottom edge of each wall panel too. Paint both scored areas with thick slip — a mixture of clay and water about the consistency of double cream — and press the first wall into place. Hold it for a few seconds, then reinforce the outside seam with a thin coil of clay. Blend the coil in with a wooden modelling tool or your finger, then smooth it with a damp sponge. Work around the base one wall at a time, checking that the corners are square. A small wooden paddle tapped gently against the outside helps keep the sides straight. If a corner gaps, add a little more slip and a fresh coil rather than squeezing the walls together. Don’t rush the joins: a candle holder carries a surprising amount of stress when it is lifted, and weak seams will show up after firing.

Supporting the form with newspaper

Once all four walls are attached, scrunch up newspaper and pack it loosely inside the holder. The paper should touch the walls gently and fill the corners, but it must not push the sides outwards. Its job is to hold the form while the seams firm up and to absorb some of the moisture from the clay. Start with a few loose balls in the base, then add more until the space is filled without force. If the walls begin to bow, remove a little paper and reshape them with your fingers. Leave the holder in a draught-free place for twenty-four hours. Check it after a few hours: if the newspaper feels damp, swap it for fresh paper. When the seams are firm enough to hold their shape, lift the newspaper out. The inside should feel leather-hard and the corners should stay crisp.

Finishing, drying and firing

With the newspaper removed, tidy the top edges with a damp sponge or a soft rib. If you want a recessed platform for a tea light, press a shallow depression into the base before the clay gets too firm, or add a short coil ring inside. Dry the holder slowly under loose plastic, lifting the cover a little more each day. Rushing the drying stage is the main cause of cracked corners. When it is bone dry, smooth any sharp edges with fine abrasive paper and fire it according to your clay’s recommendations — usually a bisque firing, then a glaze firing to around 1100°C for earthenware or 1220–1260°C for stoneware. Always place a tea light in a metal or glass cup inside the holder, and never leave a burning candle unattended. A well-made slab holder will last for years.