Coffire Art | Porcelain Art | Goodfellow Materials Hub
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Zhekai Zhang

As the last month of the year 2019 comes to an end, we have chosen to take a closer look into Porcelain and its versatile properties and applications.

Porcelain is vitrified pottery with a white, fine-grained body that is usually translucent, as opposed to earthenware, which is porous, opaque, and coarser. Porcelain is a hard material that typically feels smooth to touch.

The primary components of porcelain are clays, feldspar or flint, and silica, all characterized by small particle size. Unlike glass, clay is refractory, meaning that it holds its shape when it is heated. In effect, porcelain combines glass’s low porosity with clay’s ability to retain its shape when heated, making it both easy to form and ideal for domestic use. The principal clays used to make porcelain are china clay and ball clay, which consist mostly of kaolinite, a hydrous aluminum silicate. Porcelain may also contain alumina, a compound of aluminum and oxygen, or low-alkali containing bodies, such as steatite, better known as soapstone.

Although porcelain is often confused for china, the two are not the same. They resemble one another in that both are vitreous wares of extremely low porosity, and both can be glazed or unglazed. However, china, also known as soft-paste or tender porcelain, is softer: it can be cut with a file, while porcelain cannot. Due to its greater hardness, porcelain has some medical and industrial applications which china, limited to domestic and artistic use, does not. Moreover, whereas porcelain is always translucent, china is opaque.

Porcelain appears to be playing a more important role in technical applications such as electrical insulators and dental prostheses. But Porcelain also has exciting aesthetic properties.

One artist in particular is looking into using it to create an innovative composite mixed with food waste. Zhekai Zhang is a Chinese designer that has created a unique collection of porcelain pendant lamps called COFFIRE, using porcelain combined with recycled coffee grounds as a sustainable pigment. As the coffee oxidises it produces a red hue in marbled, random patterns and textures that make each pieces unique.

He fires the porcelain and coffee mix at a low temperature below 1000℃, and it is during this process, that the interaction between the biodiesel and the sugar in the coffee grounds oxidizes into red matter, leaving the irregular marks on the surface, influenced by many variables, such as temperature, humidity, or coffee grounds density.

Zhang, who graduated from the Royal College of Art last year, explains that natural coffee grounds are safer than the toxic metals traditionally used to colour ceramics in ancient pit firing, the oldest known method for firing pottery. Not only does he work with coffee as a more sustainable way of tinting the porcelain, he also uses a gas kiln instead of a traditional sand pit to allow the lamps to be mass-produced while avoiding the high waste rate involved in pit firing.

We spoke with Zhekai and had a chance to ask him some questions about his process and get some insight into his work.


  1. How did you start working with porcelain?

It was by chance, while I was studying my MA, and I was working on a ceramic project for Dudson. Before that, I had never had a chance to work with porcelain, so I was very excited to work on this project. As my research progressed, I found that there were thousands of possibilities for ceramic making, and I was enthusiastic to explore these further. Since then, I have developed more and more ceramic projects.


  1. What is the hardest part of working with porcelain? 

For me the hardest part is designing the shape of the piece. During the high-temperature firing, the ceramic is easily deformed in the kiln. I discovered through trial and error, that it is not possible to make some shapes with ceramic techniques. Sometimes, I have to put in time and research to find the exact combination of clay ingredients needed in order to keep the special shape.


  1. What do you like most about working with porcelain?

Porcelain is a fascinating material.  I enjoy exploring the new possibilities of materials. Porcelain is a huge stage that allows me to try different experiments. I am addicted to glazing tests, new making process experiments and mixed material.


  1. How important is sustainability in your design practice?

Sustainability is a kind of trend for now and the future, not only for designers but across all industries. I believe that today’s waste will be tomorrow’s raw material. More and more clients will be more willing to accept the circle economy and use sustainable materials to promote their products. Sustainability has already become an indispensable element in my design practice.


  1. Was it easy to introduce coffee grounds to the porcelain? Did you experiment with other waste materials?

I suppose most people have no idea about waste coffee grounds, and my COFFIRE project is a way to engage people in waste reuse in their day-to-day life. Recently, I’ve also been working with glass bottle recycling. As we all know, glass is recyclable, but not many people seriously think about the recycling process and how a material can be remade it into beautiful and unique products. Like ceramics, glass making is full of possibilities and uncontrollable elements.  I would like to create a new kind of design language though recyclable glass.

Artist: Zhekai Zhang




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