It is extremely rare to find anything new in a medium that has been in constant use for over 10,000 years, over most of the globe, in most cultures. It is impossible to be 100% certain that ceramic substrates have never been used before in the ways I will be describing, but I have never seen or heard of anyone using them as a basis for drawing and painting. The company that developed and manufactures them for an entirely different advanced-technology use informs me that this is new to them as well. My introduction to this material opened up the possibility of ceramic drawing and painting on a superfine surface. For the painter, graphically skilled artist, or anyone working two dimensionally, ceramic substrates offer exciting new possibilities not only because of their surface but also because of their durability and range of applications. After a lifetime spent largely informing people of what has been done before, it is really exciting to consider how these might be applied to a painterly/graphic use, in home decoration, lighting, as a translucent alternative for stained glass, for large- and small-format murals, and many other architectural possibilities. Beautiful miniatures and jewelry panels could also be possible when the substrates are cut to a very small size.
Ceramic substrates are high-tech, porcelain-like, super-thin, pre-fired sheets of mostly alumina that were developed for use in the automotive, electronic, avionics, medical, and military fields. They are primarily used for screen-printing digital circuitry diagrams for a variety of electronic applications. They are composed of 96% alumina, and are fired to over cone 10 (2372°F, 1300°C). Despite their thinness and lightness in weight, they are amazingly strong. Even when fired several times with an incomplete coat of glaze on only one side, there were no structural or glaze fit issues. They also have no shrinkage, which is a major benefit when you consider that regular porcelain bodies generally shrink between 12% and 17%.
If one thinks of the ceramic substrate as just another work surface to paint and draw on like paper, vellum, card, board, or canvas, it can be approached in the same way as one would for any discipline in drawing and painting. Lightweight, break resistant, and wonderfully translucent, it is paper without all the fussy curatorial issues and ceramic without all the technical issues. The only real difference would be that the materials used on the surface are ceramic.
I first used ceramic substrates 20 years ago when I tested some of my regular glazes on them and they came out of the kiln with a particularly beautiful surface quality, more so than the same glaze on other clay surfaces. So far, my research shows that they have the ability of taking on any glaze I have tried, at any temperature up to cone 10, in oxidation or reduction. They can be refired numerous times to layer glazes of different temperatures, starting with the highest and working down. I haven’t tested them in soda, salt or wood firings, because, in theory, one needs a much larger amount of silica than is present in these substrates to develop a suitable surface with sodium, potassium, and calcium (the major fluxes that bond with silica to form glaze in atmospheric or fumed firings). I don’t have kilns for these firing processes, so here might be a research area for someone else to work with and develop. Theories are made to be challenged!
I am purchasing and using what the manufacturer calls fallout material, or seconds. The cost of the material for industrial applications is extremely high and sheet sizes are generally very small. However, the fallout material is now distributed under the brand name Porcelain Canvas™ through the website www.ceramicartcart.com in a variety of sizes, with prices that are comparable to other art mediums such as good quality watercolor paper or stretched canvas. Therefore, one can do a lot of testing inexpensively. It should be noted that this is a recycled material, and as such, the sheets will vary slightly in size and thickness depending on current industrial applications. However, any variable in available formats is a small price to pay for a cost-effective supply. There may be slight imperfections, but it would take an expert to find them. The sizes that I am currently using are 5×7 inches and 7.4×11 inches, with a thickness of 0.04 inches. The 5×7-inch Porcelain Canvas costs $ 5.99 per sheet, and is available in a pack of five sheets for $29.99. The 7.4×11-inch size, costs $15.50 for one sheet or $77.50 per pack of five. A third sized sheet, which is 10.5×7.30 inches, costs $14 per sheet or $70 per pack of five. Jewelry blanks in a variety of shapes and sizes will be available soon. You can buy the firsts in many different sizes, but the prices get quite steep.
If you need a different size than what’s available or need to alter or pierce it, the sheets can be cut with a diamond saw, or you can use a CO2 laser (if you have one lying around) to cut, drill, or scribe the material.
It takes little time to adjust and feel the difference between a traditional clay surface and that of a substrate. That said, substrates do require a bit of special consideration to work with. This is due primarily to the fact that they offer no absorption, as they have been pre-fired to above cone 10. Because of this, water-based glazes and colorants dry very slowly.
I had a hunch that they would better accept glazes on the surface if the substrates were heated during application. Looking for the most convenient heating method, I stumbled on two kitchen warming trays at the local thrift store for $15. They worked perfectly. Larger warming trays may be available from restaurant supply stores. I placed a sheet of rigid copper on top of the warmer to make sure that the heat was evenly distributed throughout the substrate, which I placed directly on top of the copper.
Inexpensive trays don’t usually have a heat control. More expensive ones have rheostats that can be set for temperature control. My thrift store find gave me one of each, and I find that they both work equally well. You can also use hair dryers or electric paint strippers.
Once an initial layer of glaze has been applied to the substrate, you will need to heat it until the water in the applied glaze is evaporated, probably to around 150°–200°F (65°–95°C), or medium hot to the touch. Once the base glaze has dried, you can do brushwork, or carefully add different glazes by any method, until you have the image that you want. The substrate is then fired at the temperature and atmosphere suitable for the glazes being used. The optimum thickness of glaze will differ for almost everyone. Keeping notes on the behavior of each glaze will help in controlling the end result.
Depending on the type of artworks being done and the vision of the artists doing them, it might not be necessary to apply an overall base coat of glaze. Some methods of application can be done cold. The ivory/vellum-like surface can be drawn on with ceramic pens, pencils, and variations of Conté crayons, producing an image that is similar to regular pen and ink or pencil drawings, but fired in place, usually at around cone 6. Glaze and slip trailers in a variety of sizes are perfect for doing linear work in combination with glazes or terra sigillatas. Firing between applications of underglaze pencil, pen, and glaze to set the colors allows a complex matrix of marks to be built up.
Depending on the character of the glaze, from very fluid to very dry, the surface might be anything from smooth and flat to a definite raised line. After trying many variations of application, I find that the following four work best for me:
1. I draw and paint directly on the surface as purchased. I may do additional firings to increase complexity of the image.
2. I apply an even coat of underglaze (I prefer black) and fire it anywhere between cone 04 to 6. Then I will apply two or three coats of glaze (I prefer white) and cut sgraffito (scratch line drawings) through the glaze down to the underglaze surface. I then brush off the powdery glaze with a soft brush and fire the piece to the final glaze temperature.
3. I will sometimes apply a crystalline glaze directly to the surface in a thick coating, leaving at least ¼ of an inch bare at the edges, in case the glaze is excessively fluid. This way, it can run even on a flat, horizontal surface.
4. Most of the time, I lay down a thin glaze ground on the substrate using a small lambswool or fine cellulose sponge roller with thickened glaze (just let the solids settle and take most of the water off). After the first coat is dry, I apply two more coats, giving me a slightly pebbled texture to paint on—a ceramic version of a primed canvas. If the glaze is particularly finicky to use or paint details over, I usually fire the base coat to 1832°F (1000°C), or in a bisque firing. Although the substrate is non-absorbent, the applied glaze will be absorbent until fired to its maturity. Sometimes I use colorless glazes that are crystalline when fired and cooled appropriately. The same base glaze just fired to maturity will likely give a nicely textured background.
I have fired substrates in cone 10 oxidation and reduction, cones 6 and 8 oxidation, and cone 06 oxidation. Others, like Randy Brodnax, have tested the substrates in raku firings.
The substrate sheets accept and withstand various print-making approaches, such as monoprint, linocut, woodcut, screen printing, and decals. The potential range of applications is limited only by the creative mind and technical understanding of the person doing it. If one can imagine all the possibilities of paper, card, or canvas, substrates are just another flat, white surface waiting for the artist’s touch!
the author Robin Hopper is a potter and author of several books (available at www.ceramicartsdaily.org/bookstore). He lives in Victoria, British Columbia, Canada. He would like to thank Skutt Kilns for the nifty, custom-built 14 x 14 x 10-inch computerized test kiln for substrates. For more information about Robin, and to learn about his work and books, go to www.chosinpottery.ca.