January 12, 2009
Deliberate Cracks: Heating and Stretching to Create Crackled Texture on Pottery
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This vase by Randy Brodnax was created using the technique we outline today. |
Sometimes I feel like I was born in the wrong era because I just love old things: antiques, weathered old buildings, vintage clothing. If you can relate, then you’ll love today’s feature because we’re going to show you how to create a crackled, craggy texture on your pottery. Canadian potter Robin Hopper explains how some heating, some stretching and a little sodium silicate can transform a freshly thrown pot into what looks like a weathered antique. Jennifer Harnetty, editor. |
| Brushing the surface of a thrown pot with sodium silicate, quick-drying the surface with a heat gun or blowtorch until the surface no longer is tacky, then expanding the form from inside can give a piece of pottery an aura of instant antiquity. The sodium silicate is a thick liquid salt solution that forms a thin skin that, with applied heat, quickly hardens on the surface, encasing the soft and therefore, still malleable, clay cylinder beneath. Normally used as a deflocculant for casting slips, in this use it is quickly dried to the touch with some heat from a blowtorch. At this point, it is like a candy apple, crunchy on the outside and soft inside. When the form is then expanded with pressure from inside, the skin surface cracks enlarge in size depending on the amount of pressure and expansion. The residual sodium silicate gives a slightly glazed surface like a thin salt-glaze. Variants that will also work are a thick salt (sodium chloride) solution or sugar pancake syrup (Aunt Jemima’s, for example) solution (which produces great caramel smells from the caramelizing sugar during the firing!). The essence of the process is in the speed with which it is done, as the coating needs to stay hard and not absorb moisture from the soft clay beneath.
The process below is demonstrated by Randy Brodnax. See his finished piece above! |
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Throw a soft clay cylinder, clean the surface of residual slip, and impress with various tools. |
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Paint the surface of the cylinder with a sodium silicate solution. |
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This process is excerpted from Robin Hopper’s popular book,
Making Marks: Discovering the Ceramic Surface, available now in the Ceramic Arts Daily Bookstore. |
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Expand the soft, decorated form on the wheel from the inside, while drying with a heat gun on the outside. |
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This detail shows the decorative cracking created from heating and expanding the sodium-silicate-coated clay. |
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Robin Hopper and his wife Judi Dyelle own and operate Chosin Pottery in Victoria, British Columbia, Canada. Visit www.chosinpottery.ca to see images of their work and learn more about Chosin Pottery.
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Tags: Ceramic Decorating Techniques, Randy Brodnax, sodium silicate
Albert | July 20th, 2009 at 6:49 am
This is quite insightful. i`m delighted by this approach. I`ve been experimenting on surface decoration lately and this is very helpful.
Diana | July 31st, 2009 at 1:26 pm
Love it !! This is exciting and I can’t wait to try my hand at it .
mark | September 9th, 2009 at 11:42 pm
I made 3 of these today. I will trim the feet of them and then post some videos on youtube tomorrow., look for markspottery and you will find my vids. I used slip and iron oxide with the sodium silicate . Did not get great big cracking, will try for bigger cracks tomorrow. It is a fun process
Thea | September 23rd, 2009 at 2:57 pm
I’m going to try this on my burnished pots, feel quite excited - its going to work…. I’m sure, not hope…thanks…..