Tutorial

Tutorial

How to slab build

Slab building using soft or firm (leather hard) sheets of clay is one of the most versatile techniques for constructing both functional and decorative/sculptural pieces. While the technique can be seen throughout history and in many ancient cultures, for example the Pre-Columbian Maya civilisation where it was often combined with other hand building techniques, slab building was not as common as pinched, coiled or wheel thrown pottery in ancient civilisations. 

It is evident in many cultures and can often be identified by the shape of the object. The Korean faceted jar pictured above is clearly made of flat slabs of clay joined to form a vessel.

Historically there are a number of methods used to create slabs. The most ancient method is believed to have been to throw a lump of clay on the ground repeatedly and then to further flatten by hand, or even by trampling on it. In some civilisations, for example he Mexican people of Oaxaca, a mallet was used to pound the clay flat. For a more even surface slabs can be rolled out on a flat surface using a cylindrical object, such as a wooden dowel, bottle or rolling pin. This used in conjunction with slats placed on either side of the clay results in an even thickness of clay. Many of these techniques were developed and used independently by different civilisations and are still widely used today.

As discussed on Pottery.org (2010) it is generally accepted that there was no further evolution of the techniques until the 20th Century when the slab roller was invented. Slab rollers allow large even slabs of clay to be produced easily and quickly and slab building grew in popularity amongst studio potters in the twentieth century as a result.

In the tutorial below I will explain how to make a simple box using slabs. But much more complex, curved, textured and organic shapes can also be achieved with slab techniques. A great source book that illustrates the flexibility of the technique is Slab Techniques (Robison and Marsh, 2010). The diverse works of the following artists serve to illustrate just how versatile the technique is.

Regina Heinz uses soft slabs supported on wire and newspaper frames to create sculptural vessels and wall pieces that have a rounded soft pillow-like quality.

Christy Keeney produces figurative and abstract sculptures using slabs.

Tutorial : making a box using slabs

Step 1 – Preparation

  • Decide on the shape and size of your box and make a template out of paper.  In this example I have chosen a square box measuring 70mm x 70mm x 70mm. Remember that the clay will shrink so make allowances for this. Cut all the components out neatly and label them.
  • Take 1 kg clay, I have chosen to use Birch White stoneware, and after wedging well, flatten with your hand.  Lay the clay on a clean dry cloth (I have a selection made from old pillowcases)  cover with another cloth and use a rolling pin and guide rules to roll out the clay.  For larger pieces you can use a slab roller but for smaller pieces I find hand rolling as quick.  If you are hand rolling note that the guide rules are important to ensure an even slab of clay.
  • Start with thicker guide rules and work down to the thinner ones. Start with guide rules at 10 mm, and work down through 8mm, 6mm, 4mm and 3mm. They are most typically made of wood but Perspex or plastic also works. Turn the clay through 90° between each roll. 
  • The thickness of the clay is a personal decision.  For a small piece like this I want thin delicate slabs and am rolling them to 3mm.

Step 2  – Cutting the components

  • Allow the clay to firm up before cutting out the components as this will minimise distortion. For precise geometric shapes it’s best to work with clay that is near leather hard. Allow the clay to firm up under loose plastic for a day.
  • Use your paper template and a ruler to cut out the four sides of the box and the top that will become the lid. Fig. 6 and 7.
  • For the base it is easier to assemble if you cut a piece a bit bigger than you need.  
  • To get a precise and neat join for the sides bevel each side by 45°. You can do this by eye with a knife for smaller pieces.  For larger pieces it is easier to use a tool that has a wire at 45° to cut the clay. Fig. 8.

 Step 3 – Assembling and finishing the box

  • Start by joining two sides.  Score the bevelled edge of each side thoroughly, add slurry to both surfaces and then push together carefully.  Use a set square to help get a 90° angle for the join. Fig. 9 and 10.
  • For added strength add a small coil of clay to the inside of the join. Push this into the corner and smooth out. Fig. 11.
  • Join the third and fourth sides in the same way.  It gets more fiddly to add the coils and smooth them out but don’t be tempted to skip this as it adds strength and will help prevent cracking.
  • Place the square tube you have made onto the base piece.  Draw round the outside and inside edges. Fig. 12.
  • Thoroughly score the base piece between the two lines and the bottom of the square.  Add slurry to each surface and place the square on to the base pressing down firmly but gently to join. Fig. 13.
  • Add coils to the inside bottom edges and smooth out.  Again this can be fiddly but persevere and use your fingers,  tools or small slightly damp sponges to help with the smoothing out. Fig. 14
  • Trim the exterior of the base so that you have only a small amount round the edge.  Scrape the clay up to seal the joint.  Use metal and rubber kidneys to neaten and smooth the joint. Fig. 15, 16 and 17.
  • Now make the lid for the box.  Cut a frame shaped piece of clay that will just fit into the box, this will stop the lid sliding off the box.  Centre on the underside of the lid and mark around the outside and inside edges.  Thoroughly score each piece where they are to  join, add slurry and press together to join.
  • To make a simple handle for the lid cut a thin strip of clay and form into a loop. Centre the handle on the top of the lid and mark around it.  Score and slurry the lid and the handle and press firmly but gently together.  To avoid distorting the lid as you press the handle on place a small slab of clay under the lid to support it. 
  • Spend some time smoothing out and neatening the whole box.
  • Leave to dry slowly under plastic to allow the clay to fully equalise and minimise the chances of cracking.
  • Bisque fire the box to 950oC with the lid in place. This minimises distortion and warping and means the lid will fit better.
  • When it comes to glazing remember that any areas touching the kiln shelf (e.g. the bottom of the box, or underside of the lid) or each other must be left glaze-free, if not they will stick to each other. So if you choose to glaze and fire the lid in place on the box make sure the top of the box has the glaze wiped away.

References

Robison, J., and Marsh, I., (2010) Slab Techniques, The Ceramics Handbook Series, London, A&C Black Publishers Ltd.

Potters.org. (2010) Slab history question. [Online] Available from: http://www.potters.org/subject113006.htm [Accessed: 28th April 2019.

List of Figures

Figure 1: Anon, Mayan incense burner, ca. 400-600 AD, earthenware. [Online] Available from: https://www.mfa.org/collections/object/incense-burner-top-36222. [Accessed: 28th April 2019.]
Figure 2: Anon, Korean faceted jar, ca. 1800-1900, ceramics. London, British Museum. Photograph taken by Helen Ridgway 18th January 2019.
Figure 3: Heinz R, Shore, 1999, stoneware. [Online] Available from: http://reginaheinz.co.uk/rmh/rmh0096.html. [Accessed: 28th April 2019.]
Figure 4: Keeney C, Pipe Player, ceramics. [Online] Available from: http://christykeeney.co.uk/ceramics/#lightbox[group-56601]/12/. [Accessed: 28th April 2019.]
Figure 5: Lewis R, Ribbed Dish, year unknown, ceramics. [Online] Available from: http://www.studiopottery.co.uk/images/Roger/Lewis/14664. [Accessed: 28th April 2019.]
Figures 6 – 22: Ridgway H, How to pictures, 2018, photographs.