Deliberate Cracks: Heating and Stretching to Create Crackled Texture on Pottery

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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.

 


 

Paint the surface of the cylinder with a sodium silicate solution.

Paint the surface of the cylinder with a sodium silicate solution.

Throw a soft clay cylinder, clean the surface of residual slip, and impress with various tools.

Throw a soft clay cylinder, clean the surface of residual slip, and impress with various tools.

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.

 


 

Robin Hopper's Making Marks is about enriching the ceramic surface, the processes for doing it, and the concepts, idea development and personal research behind it. To read more and buy a copy, Click here!

 


 

Expand the soft, decorated form on the wheel from the inside, while drying with a heat gun on the outside.

Expand the soft, decorated form on the wheel from the inside, while drying with a heat gun on the outside.

This detail shows the decorative cracking created from heating and expanding the sodium-silicate-coated clay.

This detail shows the decorative cracking created from heating and expanding the sodium-silicate-coated clay.

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.

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.

 


 

For more interesting carving techniques, download your free copy of Ceramic Carving Tool Techniques: Bringing the Ceramic Surface to Life.

 


**First published in July 2009
Comments
  • This is quite insightful. i`m delighted by this approach. I`ve been experimenting on surface decoration lately and this is very helpful.

  • Love it !! This is exciting and I can’t wait to try my hand at it .

  • 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

  • I’m going to try this on my burnished pots, feel quite excited – its going to work…. I’m sure, not hope…thanks…..

  • I’ve used this method with a sodium silicate mixed with a white slip on a dark clay body with great results. The greater the proportions of sodium silicate to slip, the larger the “cracks”. By running my fingers through the silicate slip layer when partially dry, I create areas of varing cracking textures. Each piece turns out a little different depending on how long you let the slip dry. Sometimes I expand the piece a little when the slip is partially set, continue to dry and then expand to the final shape to create a pattern within a pattern. I do not glaze the textured area but let the dark/white texture contrast of the two clay bodies stand on it’s own.

  • Hi all. Does anyone know about the firing of a finished piece? Is the bisque firing at a cone 06? the glaze at a cone 5/6? Or is this more of a low firing type of clay body? Any info would be greatly appreciated!!

  • Hello,

    Today’s my first day on Ceramic Arts Daily, and I seem to have come home right here!

    I’ve been using sodium silicate for about a year. This year’s “crop” was stoneware with ochre from Continental Clay in Minneapolis – a dark, dark cone 10 body.

    I throw a very thick cylinder. Remove slip, dry with heat gun. Three coats of one or several slips, each one dried. Then sodium silicate, dried. (I guess there’s not a way to show photos here, but one would be worth a thousand words, of course.) Because of all the drying, the clay itself cracks and opens up, as well as crackling between. I also put spiral needle lines on the cylinder, sometimes planned with colors, and they open up to show the stretched clay very nicely. Expanding the clay with one hand is great fun and the best surprises come when you stop the wheel, ’cause you cannot see what’s happening while you’re doing it. I’ve made primarily round-bellied vase shapes.

    I have a background in archaeology – these pots are so fulfilling in their simplicity, use of clay that only clay could do, showing the “clayness”, spontaneity. No glaze outside over the slips, though I did try a clear glaze over a white slip which worked for me. I prefer a “natural” or even clay-colored glaze inside, to not detract from the textured matte exterior. I’ve successfully (for what I was after) used a white, tangerine, jade, seafoam and a variety of colored slips – a dry, “old” look.
    Jan

  • It is one of my favorite things to do, to make crackle pots. I have been practicing it for about 1 year and instead of a heat gun, I use a gas torch and come up with pretty interesting results. Glad to see other potters are also interesting in the Sodium Silicate process and are making various crackle pots.

  • I love the look of this, but do hand building only. I’ve seen it done on hand build pieces but am not sure how to go about it. I’d love it if someone would share that.

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