Naked raku utilizes an incompatible slip/glaze combination. The slip doesn’t fit the pot and the glaze doesn’t mature at the typical raku low-firing temperatures.
After a raku firing, the slip that is under a glaze will have a dark shadowy crackle pattern stenciled into it. With a little steel wool, the slip is easily washed away because the glaze would not stick to it, and the dark shadowy crackle pattern is revealed—the essence of naked raku.
Wanting to take that raw surface to the next level, we swapped out the plain white slip we were using for layers of colored clay. This brightened our surfaces while enhancing our nature-inspired drawings.
Colored Clay Coat
To begin, throw a thin-walled pot—we use Laguna Clay Co.’s cone 10 Amador and WSO clay bodies. When the pots are leather hard, brush on thin layers of watered-down colored clays. Most of these are colored porcelain, but we also use some white stoneware and earthenware. Allow the layers to dry for 10–15 minutes (1). By using the thinned colored clays, the color layers underneath show through when burnished.
Once the colored clays have dried, burnish them, let the pot sit for 1–4 hours to dry further, then burnish at least once more to get a glossy surface. To retain this gloss, the pot needs to dry slowly for 1–2 days. Bisque fire it to about 1427°F (775°C).
Resist Slip Coat
Next, apply the resist slip and glaze combination layers. For the resist slip, brush on a thin layer of your throwing clay (2). It adheres to the pot very well throughout the process and comes off with ease after reduction.
Our raku glaze is a mix of 65% Ferro frit 3110 and 35% Gerstley borate. The glaze is poured on to larger pots (3), but may be brushed on to smaller pieces or sculptural work. Note: Be sure that the pot is slightly warm to the touch before glazing. Tip: This glaze has a lot of Gerstley borate and will settle quickly. So, it needs to be poured right after mixing or frequently stirred if glazing numerous pots at one time.
Try different thicknesses until you get a feel for what each layer will do in the fire. Generally, the thinner layers will have tighter, smaller crackle lines than a slightly thicker glaze layer. If you glaze thick, the crackles will be very large and spaced far apart. Thick glaze can also fire out with dots and shadowy areas with very little crackles.
After the glaze has dried for a few minutes, etch a drawing through the slip/glaze layer (4). We use a wooden tool with a sharpened point. Do this gently so as not to scratch the surface of the pot. The smoke from the reduction chamber will enter the clay and create deep shadowy crackles on the surface. The etching becomes a smoke drawing on the clay surface.
We fire one piece at a time to about 1368°F (740°C). The best indication of when to pull the pot out of the kiln is when the glaze matures to an orange-peel look (5).
We create a smoking chamber by digging in the ground and filling it with wood chips. Once the pot is removed from the kiln, it’s cooled outside the kiln for about 45 seconds. As soon as we hear the glaze crackling, it’s time to place it in the smoking chamber and cover it with more wood chips (6). The hot piece is then covered completely with a metal container or lid that allows the carbon to be trapped by the clay body.
When the piece is cool enough to pull out of the smoking chamber, lightly spray it with water to remove the glaze (7). Follow this with a gentle rubbing of steel wool and water to further clean the piece and reveal the dark shadowy crackles and matte surface that is the signature look of naked raku.
Kate and Will Jacobson have been collaborating artists for thirty-five years and currently live and work in Hawaii. To see more of their work and learn about naked raku, check out, www.jacobsonartstudio.com.
Excerpted from Naked Raku and Related Bare Clay Techniques, published by the American Ceramic Society, Westerville, Ohio. Available at the Ceramic Arts Daily Bookstore, www.ceramicartsnetwork.org/bookstore.