Up until now, permanent image application options have been limited to materials that are fired onto ceramic surfaces using a kiln, requiring prolonged heating of the entire piece, which subsequently leads to an increase in the overall carbon footprint as well as an increase in production cost and working time. Unlike these other techniques, oxide fusion printing does not require the use of a kiln, allows for printing onto surfaces that are mixed media, keeps production costs low, and allows for a quick turn around by reducing the time needed for image application down to minutes.
I will be using the term “print” in this article to describe the process because, even though there is some etching that occurs, there is a visible remnant of reduced metal oxide fused to the ceramic material.
The process itself is fairly simple. Using a medium, an oxide is applied to the surface of fired ceramic (it can be a glazed surface or the fired, unglazed clay body). A laser etcher (like the Zing laser etcher produced by Epilog Laser) is used to fusion print. During the printing process, the etcher vaporizes a minuscule amount of silica material on the print surface, lending the aesthetically pleasing effect of metal inlay to the ceramic surface. Through the etching process, the metal oxide is inlaid into this groove, fusing to the ceramic material. Since the oxide fusion print cools rapidly, the color of the fused metal is consistent with the coloration and lustrous quality of the oxide fired in a traditional manner in a reducing atmosphere.
Combining the Laser Etcher with Metal Oxides
The key component of the process is the laser etcher. While there has been some development involving etching directly into clay at different stages, its application in metal inlay is a new development.
Laser etchers work similarly to a black and white printer. Instead of laying down ink, laser etchers utilize a short blast of light energy from a laser running on an X-Y axis. Laser etchers convert light energy to heat in a really efficient manner, focusing the light energy onto a focal point less than a fraction of a millimeter and vibrating the molecules on the surfaces until dissociation occurs.
This property of the laser etcher printing process makes it ideal for inlaying small amounts of oxide into the surface of the print. The integrity of ceramic material is fairly resilient to rapid changes in temperature; however, an abrupt shift in temperature can shock the material, causing it to shatter. Because the laser etcher does not rely on applied heat to raise the temperature of the print surface, there is less risk of causing thermal shock fracturing. This energy, created by the beam of the laser, can be used to heat the metal oxide powder to the point of fusion by adjusting the power and duration of the laser beam to the melting point of the metal oxide. I have found that every ceramic glaze and vitrified clay tested has been able to withstand sudden localized increases in temperatures to upwards of 3500°F (1927°C) without risk of stress to the surface in the form of fracturing. This includes low-, mid-range, and high-fired work.
Different metals have different melting temperatures: in the chart on page 55 and tiles at the bottom of that page, you can see the results of a number of different oxide metal tests. In order to find the correct laser etcher settings for a particular oxide, the oxides were run through the printing process on successively slower speed settings. The success of an oxide print is dependent on the melting point of a given oxide in relation to the duration of the laser beam. The longer the beam is focused on a specific point, the faster the molecules vibrate and the hotter it becomes.
Creating an Image
In order to use the oxide fusion printing method, a black-and-white design must be created. Both digital and traditional methods work for creating the initial image. An extra step must be added when using the traditional method as hand-drawn work must be scanned in order to make a digital copy. For my process, I am using an Apple drawing app called Procreate and then finishing the image in Adobe Photoshop or Illustrator (1). The final image is converted to a PDF, a file type that the etchers are capable of reading.
Conveniently, a canvas can be created, or adjusted, in both programs to match the exact size of the printing area. This allows for customization of each piece. I determined the print area by measuring the circumference of the pot using waxed thread (2). Once the design is ready to be printed, the print surface must be prepared by applying the oxide to the surface of the ceramic piece. The tools and materials needed are shown in figure 3.
Preparing and Applying the Metallic Oxide
In order to apply the powdered metal oxide, it must be mixed with a vehicle. The vehicle I am using for my work is isopropyl alcohol, chosen for its ability to evaporate quickly after application, leaving an even coating of powder. To achieve an even layer of oxide, I mix the oxide with the alcohol to the consistency of heavy cream (4) and then carefully roll the preparation onto the surface of the glaze with a small print roller (5). The oxide must be applied thick enough to fuse, but if it is too thick, the laser will vaporize the top layer of oxide without affecting the ceramic material underneath.
My preferred application tool, a sponge roller, applies the oxide mixture in a very concise manner at a thickness that is ideal for oxide fusion printing. Brushes are not ideal when applying the oxide mixture to the surface, because it creates ridges of oxide, which can affect print quality.
Fusing the Oxide to the Surface
Once the oxide is applied to the surface, the ceramic material is ready to undergo the printing process. The work is inserted into the laser etcher (6–8) and printing adjustments are made according to the oxide being used (9). I would suggest starting with a higher speed setting of 30 and making adjustments from there. If the speed is set too slow, it could burn out some of the oxides with lower melting points. See figure 13 for successful power and speed settings that worked for specific oxides. The floor of the etcher is then adjusted to bring the ceramic material into proper focus. For a standard laser etcher, the distance between the laser head and the focused print surface can have a deviation of up to +/- 6 millimeters without affecting print quality. Once those limits are breached, the print quality will deteriorate rapidly. If the distance is greater than 6 millimeters, the oxide fails to fuse, conversely, if the print surface is too close to the laser head, the heat energy will vaporize the material instead of fusing it. An additional tool, called a rotary attachment, enables the laser etchers to print onto cylindrical objects (see 6).
Although research is still in progress, I have compiled a list of common metal oxides coupled with their ideal power and speed setting for use with the Zing Laser etchers produced by Epilog Laser. Figure 10 shows an example of an illustrated cross section of a print onto a glazed surface. Figure 11 shows the laser etcher fusing the oxide.
The duration of the print time is dependent on the speed setting along with the size and complexity of the print. Print time for a complex, condensed, print averages in at 2.1 minutes per 1 square inch.
Once the ceramic print is run through the print session, the work can be removed and the oxide brushed off (12) into a container for later use. The oxide is easily brushed off with a stiff paintbrush, leaving only the fused metal behind. The ability to collect the unfused oxide results in a print that uses almost negligible resources, making this an efficient and more sustainable image transfer method.
I am excited about the possibilities surrounding this new method of applying imagery on ceramics and hope that other makers can explore oxide fusion printing on their own work. If investing in buying or leasing a laser etcher is not right for you, many maker spaces offer access to equipment like this for reasonable fees.
the author Rachel Clark received her BFA from Tennessee Technological University’s Appalachian Center for Craft. She is currently working toward an MFA in ceramics from East Carolina University in Greenville, North Carolina.
Information for this article was sourced from “The Royal Society of Chemistry.” The Royal Society of Chemistry, 2017, www.rsc.org, a professional association in the UK with an extensive database of chemical information.