Through a series of experiments, I developed a method for 3D printing incredibly thin pieces from pure porcelain clay. Surprisingly, the lightweight forms maintained their shape during the high-firing process without requiring any additional support. The reason for this is, despite their fragile nature, the pieces did not collapse under their own weight when the porcelain softened at the high temperatures in the kiln.
This fascinating discovery inspired me to scale up my work. Encouraged by the potential, I built a new machine, twice the size of my previous one, designed to simultaneously form both thin and large porcelain pieces—something previously unattainable with existing methods. After months of meticulous calibration, I printed the first piece, measuring an impressive 1.5 meters in height. Unfortunately, it collapsed during firing and fell onto the kiln wall.
Undeterred by this setback, I remained convinced that creating such a large form was possible. Over the next three years, I devoted myself to a painstaking process of trial and error. Only after making 26 pieces did I finally discover the recipe that enabled me to achieve the desired scale. The process was long and challenging, but the result is something once thought impossible.
As I delved deeper into the intriguing world of large-scale porcelain, I encountered a variety of unique challenges. One particular issue was the remarkable shrinkage of the material that increased proportionately to the size of the object; in fact, the piece shrank by an astounding 30 cm (12 inches) in height between the forming stage and the completion of firing. This very reason is why porcelain is typically reserved for smaller pieces and is considered the most difficult type of ceramic to work with.
Inevitably, such significant shrinkage led to the development of cracks and deformations within the piece. Faced with the importance of maintaining uniformity at each stage of the process, I realized that I needed to employ extreme precision. By harnessing the capabilities of my machine and developing new tools and techniques, I was able to attain a level of accuracy that allowed the material to be pushed beyond its conventional boundaries. This meticulous approach, which involved diligently maintaining consistency throughout, successfully alleviated tension build-up and averted potential damage during the firing phase.
While exploring the rich history of porcelain, I have observed the various techniques employed by people when faced with the challenge of creating large-scale porcelain pieces. Some opted for a less pure, stoneware-like clay, which can be fired at lower temperatures. This method effectively reduced shrinkage but resulted in a somewhat yellowish and coarser body. In order to imitate the desirable qualities of porcelain, such as its whiteness and smooth texture, they covered the pieces in a thick layer of glaze to conceal the impurities within the clay.
On the other hand, a few remained committed using only pure porcelain, despite the challenges it posed for large-scale works. In order to overcome these obstacles, they limited their designs to radial forms. This restriction allowed for better balance, equal weight distribution, and the ability to trim the piece using a wheel, which was crucial for achieving the thinner, uniform walls needed to withstand the firing process.
In embracing the essence of porcelain and the complexity of asymmetrical forms, I faced many unexpected challenges and obstacles. Through a careful examination of each experiment, I gained invaluable knowledge that informed my subsequent attempts. Success in making a large, irregular form ultimately lay in striking a delicate balance between uniformity and structural support.
To achieve this balance, I improved my 3D printing process to introduce a subtle variation in wall thickness, which allowed me to create a piece that maintained its structural integrity while preserving its lightweight nature. The wall thickness tapers gradually from the base to the rim of the piece, ensuring a graduated distribution of material throughout.
A key challenge was determining the ideal thickness ratio, striving to minimize differences in thickness while providing enough strength. Significant variations in wall thickness can lead to internal stress build-up due to differing drying, heating, and cooling rates of the porcelain clay. Ultimately, these stresses can result in cracks and deformations in the fired piece.
To ensure uniformity during the drying stage, I focused on creating a humidity-controlled chamber that could regulate the drying process. After experimenting with various prototypes, I built a chamber that extended the drying process to a period of 10 days, allowing the piece to lose water content evenly across its entire surface. It was crucial to prevent the formation of microcracks before firing, as these imperfections would expand during the process and ultimately compromise the structural integrity of the piece, leading to its collapse.
The firing of a large porcelain piece in a kiln presents a unique set of challenges, particularly in terms of temperature variations throughout the individual piece. As the kiln approaches its peak temperature during the final moments of the firing process, the porcelain undergoes a captivating transformation.
During this critical stage, the clay minerals partially melt and rapidly compact, causing the porcelain to shrink and soften. In the hotter zones of the kiln, the rate of shrinkage accelerates, resulting in a greater contraction of the porcelain in those areas. This uneven shrinkage leads to an imbalance in the piece, and as it continues to contract while remaining soft, the porcelain ultimately takes on a distorted, bent shape.
To overcome this challenge, I revisited an ancient tool called the saggar. Traditionally, saggars were used in wood-fired kilns to shield delicate porcelain surfaces from ash and debris. I adapted this concept, creating a kiln-within-a-kiln to provide a more controlled environment for the firing process.
I 3D printed my own thin and lightweight saggars using refractory clay, designed to be as light as possible to minimize any disturbance to the kiln's operation due to the extra material being heated and to reduce energy consumption. These custom-made saggars were then stacked around the piece before loading it into the kiln. The 3D printed saggars allowed for more consistent heat transfer through radiation, ensuring that the temperature difference across the entire piece was minimal—only a few degrees.
Once I achieved consistency in forming, drying, and firing a large-scale porcelain piece without any cracks or deformations, I shifted my focus towards the integration of color. The kiln's atmospheric conditions produced a snow-white, refined surface, providing an immaculate canvas for adding color.
To emphasize the purity of the porcelain and reveal its true surface without any concealment, I opted to blend the pigment directly into the clay, rather than applying a glaze afterward. Cobalt oxide was my pigment of choice, as it is capable of withstanding the high temperatures required for the single firing process. By integrating the pigment into the clay, I aimed to demonstrate the use of pure porcelain, ensuring that nothing was hidden or obscured beneath an additional layer.
By limiting the amount of cobalt added to the clay to an absolute minimum and applying it solely as a thin layer on the outside of the stream rather than mixing it throughout, I was able to maintain the structural integrity of the piece. This approach ensured that only a minimal amount of cobalt was present on the outer surface, thereby preserving the porcelain's inherent melting point.
In this aspect, uniformity was equally important. Given that cobalt lowers the melting point of porcelain clay, an uneven concentration could potentially undermine all previous efforts. Striving for uniformity while pursuing dynamic coloration, I developed a technique to ensure an even distribution of cobalt oxide throughout the piece.
By seamlessly merging a continuous stream of white clay with another containing cobalt oxide within the 3D printer's nozzle, the piece was simultaneously colored and formed. The geometry of the form and its position within the machine, in relation to the juncture of the two clay streams, dictated when the cobalt blue would emerge on the surface or remain hidden. Each transitional phase produced a variety of blue shades, even though the pigment concentration remained consistent across the entire work.
Instead of applying a predetermined decoration to the porcelain piece, the distribution of cobalt oxide was dictated by the form itself. The piece's contour lines were emphasized by sharp color changes, creating a striking contrast along the ridge. At the same moment, the subtler gradients emerged from the form's curvature, yielding a harmonious interplay of shades that mirrored both the structure and the way light interacts with its surfaces. This approach allowed the work to express its own visual language, underscoring the importance of the preserved form in determining the final appearance.
Throughout the entire process, I regularly mirrored the shape to verify if my findings also where valid for other forms. Compared to symmetrical forms, which maintain their identical appearance when reflected, asymmetrical forms produce completely different shapes upon mirroring. It was only after I successfully crafted a pair of perfectly mirrored pieces, identical in both form and color, that I recognized I had attained full control over the entire process.
The three-year journey to create this large-scale form in true porcelain has been one of immense challenge, dedication, and discovery. It required a reimagining of traditional techniques, the development of innovative tools and methods, and an unwavering commitment to understanding the complexities of porcelain's behavior at every stage of the process.
The 26 pieces embody my extensive research and tireless efforts to expand the horizons of porcelain. Each experiment, whether it showed a significant breakthrough or a setback, provided precious insights that compelled me to continue my exploration.