If left overnight, the borax wash mixture will harden. For example, when 1 tablespoon of tin oxide is added to a OM 4 ball clay base terra sigillata and granular borax is sprinkled onto it, the result is a vivid pink color around the edges of the melted borax pool (1, 2). It also tends to gather and pull colorants away from the terra sigillata below, which can result in some beautiful effects. The result of the melted granular borax is a glassy pool with an amber-color cast. Granular borax can be sprinkled onto a terra sigillata surface, and if enough of the material lands and settles together, it will create its own glaze-like melting at low-fire temperatures. Borax, as a wash at the 1:6 ratio, will create tiny iron-like speckles on a terra-sigillata surface. The powdered form dissolves more easily in warm water, but is really more of a convenience than a necessity. Boraxīorax can be used in its granular form or powdered form. In my own practice, I don’t burnish the terra sigillata and instead use the salt or soda ash wash at the 1:3 ratio to create a sealing sheen on the terra sigillata. In the more diluted ratio of 1:6, soda ash and salt washes make soft, circle-like patterns, however the shape of the patterns varies in subtle ways. Soda ash and salt provide the most similar results at the 1:3 ratio, but vary more at the 1:6 ratio.īoth soda ash and salt tend to darken the terra sigillata color and also create a low-satin sheen at the 1:3 ratio. If you’re working in large-scale or large-quantity, you will want to increase your wash batch size accordingly. You can use hot tap water, and less of the material will dissolve into the water, which will then deliver more variability to the terra sigillata surface.įor small-scale work, a 1:3 ratio wash batch of 2 tablespoons of materials plus 6 tablespoons of water is a good amount to get started. When making washes, the use of boiling water helps to fully dissolve the materials and as a result provides a more consistent application. Suggested materials used to make washes include: soda ash, salt, borax, and lithium carbonate. The 1 to 3 ratio is more concentrated and produces more noticeable results, while the 1 to 6 ratio is more diluted and produces softer, subtle changes in surface, color, and texture. Washes are used at varying concentrations: most commonly 1 part material to 3 parts water or 1 part material to 6 parts water. Washes are most often used in low-fire applications, but some artists also use them in mid-range and high-temperature firings, where the firing process provides the additional surface reaction, rendering the wash layer less necessary. WashesĪ wash, in this context, is a flux material mixed with water that’s applied over terra sigillata before or after the bisque firing. While a wash, or flux wash, adds a sheen and sometimes texture to the terra sigillata surface, a patina enhances the terra sigillata surface because it’s a thin, colorant-rich wash layer that settles into the subtle markings on a surface. Washes and patinas offer ceramic fired surface options that provide variations in texture and colors when applied over a terra sigillata. With these inherent qualities, terra sigillata lends itself to being adaptable to layers of additional materials, which creates a multitude of potential results from the combination of a few materials. Other desirable traits of terra sigillata include its thin, skin-like covering and its reactivity to other materials and firing processes. As a result, this uniform color can flatten the volume of a given form or, conversely, the flatness of the terra sigillata color can be used to color block areas, highlighting the form. One of the characteristics of terra sigillata is the uniform opaque color created when it’s applied in multiple layers. Pottery Making Illustrated Submission Guidelines.
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