Texture from Within: Mixing Coarse Materials into a Smooth Clay Body

Add texture to your clay for interesting effects!

mixing coarse materials

When most people think of porcelain, they think of a velvety translucent white surface. But Gillian Parke was interested in that white surface, but with a little more texture.

In today’s post, Gillian shares her technique for getting a very coarse surface texture from a clay body typically chosen for its creamy smooth consistency.  – Jennifer Poellot Harnetty, editor.

mixing coarse materialsI usually work in stages on a set of pieces using Highwater Clay’s Helios porcelain with coarse Custer feldspar (1-10 mesh, Seattle Pottery Supply) and 50-80 mesh molochite wedged in. Throwing with the inclusions requires using a substantial amount of water to provide sufficient slip for lubrication. This helps prevent both finger cuts and tears in the turning clay. However, the piece will lose its strength and collapse due to the low plasticity of porcelain if too much water is used.

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Each stage is thrown on the wheel and allowed to dry. Before removing the piece from the wheel, the feldspar and molochite matrix is exposed with a metal rib or trimming tool. This also serves to remove the surface slip. After assembling the piece, it is completely dried and wax resist is painted onto areas that will eventually be glazed. Underglaze is then applied to the unwaxed clay areas. The underglaze is removed from the surface with a damp sponge, leaving an underglaze patina that accentuates the feldspar and throwing lines.

mixing coarse materialsWax resist is again applied to the dry surface. Using a needle tool, lines are etched through the wax, revealing the clay below. After wiping clean with a damp sponge, black underglaze is applied to the inlaid line. After bisque firing to cone 07, wax resist is applied to black inlay lines so that glaze will not cover the line and affect the color. Glazes are applied by pouring, dipping and/or brushing. The resulting piece is then fired in a gas kiln to cone 10 in reduction.

Feldspar inclusions result in pearl-like eruptions covering the surface of the vessel. This surface is painted with various luster overglazes and fired in an electric kiln to cone 017 multiple times per layer of surface treatment.

**First published in 2015.
  • Vicki C.

    Gillian, I think your work is beautiful. Thank you for sharing this unusual technique. I only work with porcelain and have often considered the inclusion of other materials to achieve a textured surface. This has given me food for thought! : )

  • Marian P.

    What is the best way to add coarse materials to the porcelain? I’d love a fairly detailed explanation of this process.

  • Steve M.

    I had Custer Corp send me a bucket of unground feldspar they use years ago and had fun crushing and sieving the resulting chips through a pool filter basket. Tough on the hands but great results! And when My wife Sarah and I drove cross country we visited the company offices in Custer South Dakota and saw the grinding facility as well, cool place!

  • Subscriber T.

    And I agree with Jonathan 😉

  • Subscriber T.

    I love Gillian Parke’s tecnic, is incredible, amazing.

  • Gillian P.

    Thanks all for such great feedback. There are several reason why I use porcelain, technically and aesthetically. First, I LOVE throwing with porcelain and don’t really enjoying using other clays. I love the white surface and ringing sound of fired porcelain. Personally, I have fond memories of my gran taking me to the china shop when we would visit her in N Ireland. I have experimented using this technique with other clays but stoneware and earthenware had too much tooth and when I threw with it, it cut my hands. The porcelain slip that forms while throwing lubricates the clay and I find it easier to throw. Technically, the porcelain fluxes better and I found that I needed the higher temperatures and the extra flux to melt the feldspar inclusions the way I wanted them to be. I like the pieces of feldspar to be beaded up and the inclusions did not respond the same way in stoneware. There is no reason not to do it the other ways suggested but that is not what want to do. I enjoy finding ways to combine and contrast porcelain with shigaraki ware. I have also experimented with organic inclusions (couscous, rice, etc) but the mess from moldy recycled clay wasn’t fun enough to continue.

  • Mary P.

    The technique is beautiful. I wish the images were larger so it you could see more clearly the texture the technique produces.

  • Hannah I.

    I am looking for a textured granite or other light colored stone appearance after cone 5/6 firing – I use a white stoneware clay I am happy with, but would consider adding something or changing clay body. Would prefer a non-glossy glaze if there is one (looking for the texture on the outside primarily) – once saw a photo and read about a “granite glaze” that was perfect but can’t find it.

  • Teresita C.

    I agree with Jonathan ,after teaching ceramics for nearly twenty years, that there are many ways to add texture to a slip or a clay body. But Gillian´s technique is unique. The picture just doesn´t make justice to the piece.
    The surface she achives worth the price of the materials.
    Years ago when she was experimenting it had the opportunity to hold them.
    I highly encourage the readers to give it a try, They won´t regret .

  • Patti C.

    Hannah, you might be interested in trying mixing underglaze with a clear glaze for various non-glossiness’. It won’t have a granite texture but does give an interesting surface. One part glaze to one part underglaze is a good starting point. (I don’t mix my own glazes so am limited to playing around with what is available commercially)From there you may be able to develop a “granite” appearance.

  • Nigel C.

    Why use porcelain if you want texture – its a little expensive ??? But aside from that, try adding sawdust – this will burn out leaving an interesting textured surface depending on the grade, as will perlite, which is a volcanic glass – this will leave craters and small beads of glass once glost fired. Another way to add texture is to apply a slip containing course materials to the green ware – powdered glass in the slip will result in small glass beads once glost fired.(at lower temperatures ie bisque it can look a little dull as the glass will not be fully melted)

  • Neal O.

    I first saw Gillian’s work at the Carolina Designer Craftsman show a few years ago and fell in love with it. I think the point of porcelain is the contrast between areas with it and areas where there are the feldspar inclusions.

  • Jonathan G.

    While there may be easier ways to get texture using other materials, I don’t think this is necessarily the point of this technique. There is very little else like the shigaraki and other feldspar inclusion ware that has these textures. I wonder if the other techniques would produce the same texture?

    Using porcelain makes sense athstetically – it would be difficult to get the bright surface decoration and milky contrasts and still include the lumpy texture using a a white slip on stoneware alone.

    Bravo for developing this intriguing technique.

  • Ann H.

    Nigel- I work almost exclusively with porcelain now, but I’ve always loved the course nature of what looks like little melted stones- I dislike the grays I get with celadons and ash glaze over stoneware, I prefer the bright white color or the porcelain, and these days with porcelains what they are they become translucent and glow with the light at a thicker state than ever before it’s very cool. I know they’re crazy expensive but they’re like caviar you don’t eat it everyday… =)

  • Nigel C.

    Jonathan – its only an observation – you can get the same effect using smooth white stoneware or earthenware – and they are cheaper!!!

    There are dozens of materials which will give texture to ceramic forms when applied to the clay or as an ingredient to slips – the only limit is your imagination. Try straw, horsehair, ground shells, even ground coffee etc.

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