Wednesday 9 June 2010

Surface Tension

We take the forces at work around us for granted most of the time, hardly realising that everything in nature, even a drop of rain, is as it is because of universal forces. Forces and structure pressing outward, weight and pressure pressing inwards, and the point of balance between those forces, the border line that defines a form, we call the surface.

When forming clay on the wheel, it is the task of the potter to remain still while those forces work against our hands and find balance in the shape of a pot. Once taken from the wheel and allowed to dry partially, the clay shrinks and there is a certain tension in the surface when the pots are returned to the wheel for trimming. The trimmed surface is therefore different in character than the unaltered thrown surface. I have always found the play between these surfaces delightful. I therefore try not to interfere with that too much by cluttering it with decoration.

When doing a collaboration with a french restaurant a few years ago, however, I needed to add a rim motif. I am not one for drawing pictures of things on pots, so I created a small design which extends the idea of surface.

If one scratches a line in leather hard clay, the edges will tear, leaving a jagged and messy edge. If you cut the same line with a sharp tool so as to pare away the clay the edge is sharper and far more energetic. Using a hoop tool with an acute angle I cut an exclamation mark. Below that I add three dots, compressed with a cone shaped wooden tool. As the clay from the dot is not removed from the surface it moves into a raised crater like edge, giving these indentations a different textural character than the cut mark.

Beside these incised and compressed marks I add, literally, a drop of slip. Slip, or engobe, is a liquid clay used for decoration. In order for the slip to be compatible with the clay I use the same porcelain for the slip as that which constitutes 75% of the clay body. The shrinkage of the slip is, therefore, exactly the same as the clay, so there is no chance of cracking or flaking. One slip I make fairly viscous, and add 2% of Copper Oxide. I apply this with a thin metal rod as a single drop, touching the end of the rod to the clay surface and allowing surface tension to pull the slip into a circular droplet on the rim of the bowl. I prepare a second engobe which is thinner, with 2% of Chrome Oxide, and, using the same metal rod, I touch a droplet to the surface of the pot then flick the end of the rod away, once again using surface tension to create a dynamic elongated tear drop shape.

These applied engobes give a raised pattern which counterpoints the intaglio incising and impressed marks on the rim. When fired, the pure porcelain of the engobe becomes slightly glassier than the clay body. The Copper becomes red in the reduction, a form of "Shinsha" glaze, and the Chrome becomes green. Combined with the flame colour of the clay, the Igusa straw markings and tenmoku glaze, this small motif adds a subtle and dynamic accent to the rim of the vessel which is rich in visual and tactile information.

We interact with nature and the world around us on many levels, and tactile beauty is just as important in art as visual beauty, more so for those without the gift of sight. By utilising surface tension and the forces of nature, energy and tension can be expressed intimately in the surface of a vessel.


  1. i think it's not only the rim treatment but the centre black glaze that completes the tension on these plates and the engobe markings that look like toffee.. blending the clarity between what is food and what is plate...stunning work EC

  2. Please elaborate on the Igusa straw markings...

  3. Really interesting thoughts. Never thought about the texture of rims before. I will hereafter. Thanks for sharing.

  4. Thank you,
    Rims are very important, as that is the only part of a plate that is really seen when the food is served. Many potters concentrate on the centre decoration, like a picture, and treat the rim just as one would a picture frame. That's fine if the plate is only for a wall, but not so if it is for food as well.
    I will write an entry later detailing the igusa, but if you go through some of my archives with "technical" or "stacking" labels you will find more information there.