Topic: Articles

Resist Erosion Raku

image-06

 

Serendipity, happy accidents, and the element of surprise are all hallmarks of working with raku. From the first pot that Paul Soldner’s students accidently dropped in leaves, to his famous halo effect and a multitude of other raku discoveries, it’s often the unexpected result that has been most exciting. It’s in this spirit of playing with the medium that I stumbled on an interesting technique for adding texture to the surface of my pots.

Having worked with copper-matte glazed raku for over 30 years, I kept my work as smooth as possible in order to enhance the color response on the surface. I wasn’t even thinking about adding texture to my pieces when I came upon a technique using resist with erosion to decorate the surface.

After purchasing a copy of David Roberts’ 2nd edition of Painting with Smoke, I tried out some of his naked raku techniques. Two of these techniques came together, leading to my textural discovery. I had been using Robert’s sacrificial slip and glaze technique, drawing a scribble line through slip and glaze, and getting some interesting results. Then I decided to try his method of creating multiple levels through erosion, a technique in which wax is applied to specific areas on a leather-hard piece, leaving un-waxed areas that can later be eroded by rubbing with a wet sponge. Serendipity took over when I decided to wax the surface of a test tile and then scribble through the wax before eroding the surface. The results were magic!

Step-By-Step Procedure

Create a piece to be textured. I find that round, closed forms work best. Most of my work is thrown using a low-fire talc body that I have raku fired successfully for many years, but any good raku clay will work, the smoother the better.

Terra Sigillata and Wax Resist Coats

Once the piece is bone dry, apply several coats of terra sigillata (1), burnishing each layer with a thin plastic bag before applying the next (2).

Figure 1.

Figure 2.

When the last layer of terra sigillata is dry, wax the areas that you want textured I use the same liquid wax resist that works well for protecting the bottoms of pots when glazing (3). One coat of wax is enough.

Figure 3.

Wax Resist Drawings

Once the wax resist is dry, use a toothpick, wooden skewer, or semi-sharp pencil to draw through the wax (4). I have used a scribble line that includes overlapping loops or a controlled, meandering line that never crosses itself, and a straight-line variation of the scribble design (5). Each gives a different result.

Figure 4.

Figure 5.

Eroding the  Wax

Using a wet, medium-sized sponge, rub the waxed surface (6). I use a circular motion. At first the design remains intact, and the water just etches lines where you scratched through the wax. Continue to rub and erosion takes over, not only eroding the clay more deeply but also breaking up the design and creating something new. Continue turning your work as you erode the surface, so you don’t overdo it on one area.

Figure 6.

Bisque Firing and Rewaxing

Bisque fire the piece. There is little agreement on bisque firing temperatures for terra sigillata. I bisque fire to cone 06 and still have plenty of shine on my burnished pieces.

Using wax resist, re-wax just the raised, textured surface (7). Applying the wax is tricky. I use a 3-inch hake brush dipped lightly in wax and wiped fairly dry on the edge of the wax jar. It takes a light touch and a deft hand to get the wax on just the raised surface. A little bit of a curve to the bristles of the brush helps. I have experimented with applying dry wax, using the edge of a crayon, but liquid wax works better. This layer of wax will resist the copper-matte solution in the next step and allow the raised texture to become shiny black after raku firing.

Figure 7.

Applying Color

When the wax resist is dry, spray the piece with a copper-matte solution (8). Some of the solution always beads up on the waxed surface, so I gently paddle the raised surface with the flat side of a stiff bristled brush after the piece is dry to remove it from the wax without affecting the recessed portion of the pot.

Figure 8.

Caution: Always wear an approved and fitted NIOSH respirator mask and protective gloves when spraying the copper-matte solution and when cleaning the waxed surfaces. Use a spray booth (if you have one) to contain the solution.

Raku Firing

Fire your piece to 1742°F (950°C). Then cool it in the kiln to 1292°F (700°C).

Timing is critical for this next step, so set a timer. For small pieces (grapefruit size or smaller), I set the timer for 7 minutes. For larger pieces (10 inches in diameter or larger), I set it between 12 and 15 minutes. Start the timer.

Remove the piece from the kiln and place it on a nest of combustible materials—I like to use newspaper and pine needles for reduction, as they leave interesting marks on the piece—situated on a bed of sand that is at least three inches deep (9 and 10). As soon as the paper flames up, add more shredded paper on top of the piece (11). Once flames engulf the piece, cover it with an inverted metal can, sized to fit the piece being fired, and push the rim of the can into the sand to create an airtight seal (12).

Figure9.

Figure 10.

Figure 11.

Figure 12.

When the timer goes off, briefly lift one edge of the can covering the piece, just enough to burp some oxygen into the chamber. Set the can edge back down in the sand. Wait a few more seconds then remove the can (13). Often the piece has a copper-penny pink color overall. This slowly starts to change as color grows on the piece. When you see color that you like, spray the piece with water mist from a pressurized pump bottle to set the color (14). If you are not happy with the color, you can re-fire the piece.

Figure 13.

Figure 14.

Cleaning and Protecting

When completely cool, most pieces only need minimal cleaning. Brush off any scraps of paper that may have stuck to the surface. I spray my copper-matte pieces with a grout sealer to prevent the color from changing. So there you have it, a new way to add texture and a little magic to your pots.

Joe Clark is a retired art educator and active raku potter, living in Port Edwards, Wisconsin. 

Subscriber Extra:

Comments

Comments are closed.

Enter Your Log In Credentials
This setting should only be used on your home or work computer.

Larger version of the image

Send this to a friend