The Ned Foltz workshop (described in Sgraffito Plates, Part 1) got me quite excited to create more sgraffito plates, so, of course, I went straight to my studio to experiment a bit on my own! In addition to having fun playing around with sgraffito, I also wanted to figure out what types of clay would work best with the technique (not as exciting, I know). My standard clays, a red stoneware and a cream stoneware, both contain grog (small grains of clay that have already been fired). I love working with grogged clay because my tiles are much less likely to warp than if I used perfectly smooth clay. But grog has drawbacks too. The grog can leave jagged edges on the clay that are difficult to smooth, and I have read other places that grogged clay is not good for sgraffito for this reason.
Sgraffito Coasters: red grogged stoneware clay was coated with white stoneware slip and carved. Finished with colored glazes.
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Well, my sgraffito coaster sets (mentioned in Part 1) were all made with my grogged red stoneware coated with smooth white stoneware slip, and they turned out pretty well! The carved edges did have a bit of a texture to them, but I don’t think it really detracts from the piece. Carving through grogged clay, however, does wear down the carving tools quite quickly!
In addition to my two grogged stoneware clays, I have also begun experimenting a bit with a brown smooth stoneware and a white smooth stoneware clay. These, I have found, take a bit of extra care to use. Since they don’t have grog, they are more likely to warp and crack while drying, and I have to make sure to dry them extra slowly to minimize this effect.
So my first round of sgraffito tests consisted of a few square plates and some small bowls constructed from different clays.
In addition to my two grogged stoneware clays, I have also begun experimenting a bit with a brown smooth stoneware and a white smooth stoneware clay. These, I have found, take a bit of extra care to use. Since they don’t have grog, they are more likely to warp and crack while drying, and I have to make sure to dry them extra slowly to minimize this effect.
So my first round of sgraffito tests consisted of a few square plates and some small bowls constructed from different clays.
Project:
Sgraffito Plates
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Materials:
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Improvised Hump Molds: glass bowls and a wooden plaque blank
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Step 1: Making the Plate Blanks
I wanted to hand build the plates using hump molds, as was demonstrated in the Ned Foltz workshop I attended (see Part 1). A hump mold, or drape mold, is a positive form over which a slab of clay is draped to form a vessel the shape of the mold. The hump mold is usually made from a porous material such as plaster or bisque clay, and they are commercially available. However, I ran into a small problem: I don’t have any hump molds!
So, I improvised. I grabbed a few old Corelle bowls I had sitting around and a square wooden plaque blank I had picked up from a craft store a while ago, and decided that they would suffice for interim hump molds. The porous nature of a real mold wicks moisture from the clay and allows the clay to be more easily removed from the mold. Since my substitute molds were low- to non-porous, I realized that I may have a bit of difficulty removing the clay!
I use my improvised hump mold as as template to cut a circle out of the slab of clay. I place the circular slab onto the mold, form it around the mold and clean the edges. After the bowl has dried a bit, it is removed from the mold.
I then rolled out my slabs of clay. Most of the slabs I rolled to a thickness of ¼”, however, I rolled one slab of smooth white stoneware to a thickness of 3/8” just to see if this thickness worked well. I made a slab using each of the clays I currently have on hand: a red grogged stoneware, a cream grogged stoneware, a brown smooth stoneware and a white smooth stoneware. I then cut the slabs into a circle or square of the size desired for my bowl or plate.
I draped the slabs over my makeshift molds, trimmed any excess clay as needed and then smoothed the edges. I let the clay stiffen up for a few hours in the studio, and then since I was worried about them sticking to the non-porous forms, I loosened them so they could be easily removed. The bowl should be dried on the mold until it can be handled without warping. Don’t keep the bowl on the mold too long! Since the clay shrinks as it dries, the bowl can become too small for the mold and crack.
The clay was allowed to dry overnight to a leather-hard state where the piece could be moved without warping, but was not too dry. At this point, it was time to apply the slip and do the actual sgraffito!
I draped the slabs over my makeshift molds, trimmed any excess clay as needed and then smoothed the edges. I let the clay stiffen up for a few hours in the studio, and then since I was worried about them sticking to the non-porous forms, I loosened them so they could be easily removed. The bowl should be dried on the mold until it can be handled without warping. Don’t keep the bowl on the mold too long! Since the clay shrinks as it dries, the bowl can become too small for the mold and crack.
The clay was allowed to dry overnight to a leather-hard state where the piece could be moved without warping, but was not too dry. At this point, it was time to apply the slip and do the actual sgraffito!
I applied slip to the leather-hard pieces with a soft bristled brush. The goal is to get a nice, even thickness of the slip over the surface, which usually amounts to 2 to 3 coats of slip. Thin spots will show the clay color underneath when fired, so it is important to have good coverage. I noticed that while the brush strokes were visible in the slip as it was applied, they disappeared on the final plate after it was fired.
Step 2: Applying the Slip Overcoat
The leather-hard greenware bowl has been coated with red and yellow underglaze in preparation for sgraffito.
In addition to various clay bodies, I decided to experiment a bit with the slips as well. To my red grogged stoneware bowl I applied just the white stoneware slip since I thought the red and white would contrast well. I also had some white porcelain slip, so applied that to one of the brown smooth stoneware plates. For the white smooth stoneware bowl, I decided to color the porcelain slip with a blue mason stain. Then, for my cream grogged stoneware I decided to use colored underglazes instead of slip. I used a burgundy and a purple underglaze to create a faded ombre effect. I had an extra plate in brown smooth stoneware, so I decided to use underglazes on that as well in a brushed-on painting style with reds, oranges and yellows.
Step 3: The Designs
The next step was choosing the designs for the pieces. This can be anything from free, public domain designs, or something from your imagination. In the past couple months I have been doodling a bunch of mandala-like circular designs that I though would be perfect for the bowls.
A few round sketches for possible sgraffito designs.
Some people enjoy sgriffitoing free-hand onto the piece. I prefer using a template since my designs tend to be a bit complicated. I touched up my doodles, scanned them so I could open them in a photo editing program, and resized them to the dimensions of the bowl. I then used a printed copy of the design as a template to trace the design onto the face of the bowl. Since a flat sheet will wrinkle and crease when placed on the concave surface of the bowl, I also experimented with tracing the design onto a piece of thin plastic since it is more flexible than paper and using that as the tracing template. I think I prefer the plastic a bit over the paper for bowl, though either way works!
Sgraffito design templates printed on a sheet of paper and drawn on a piece of plastic with a Sharpie.
I use a ball tool to trace the design from my template to the bowl. However, any implement with a rounded tip will work as a stylus – just make sure the tip is not so sharp that it tears through your template. The ball tool leaves an indentation in the slip that will be used as a guide while carving the clay. Any uncarved indentations will show up in the final firing, so be careful while tracing!
Even if the design is complex, I find it easier to have a simpler template similar to the template on plastic shown in the picture above. Trace only those lines that are needed as guides, and carve in the details freehand. Since your template will warp on a curved surface, it is often easier to adjust design elements to the curvature freehand during the sgraffito process.
Even if the design is complex, I find it easier to have a simpler template similar to the template on plastic shown in the picture above. Trace only those lines that are needed as guides, and carve in the details freehand. Since your template will warp on a curved surface, it is often easier to adjust design elements to the curvature freehand during the sgraffito process.
Step 4: Sgraffito
Sgraffito tools.
After tracing, I carved out the design. I use my tracings as guides, removing the slip where the lines were and adding extra carved details as needed. I varied the line width here and there, adding interest to the pieces.
You can carve as deeply or as shallow as you like. For the pieces that have a grogged clay base, I tend to carve shallow line, trying to remove only the slip or underglaze and leaving the clay beneath in tact. Otherwise, deeper cuts on these pieces leads to rougher lines due to the grog. With smooth clay pieces, carving deeper into the clay underlying the slip or underglaze can create really interesting textures and varied surfaces.
The carving, or sgraffito, can be accomplished using a variety of tools. In my past forays into sgraffito, I primarily used a commercial sgraffito tool. The tool has a loop of wire on either end that can easily carve through the slip, and leaves a nice line. The dental tools I use for carving plaster make good sgraffito tools as well. The pen tool (mentioned in Part 1), which also works quite well, can remove a bit more clay in one pass than the loop tool. And of course you can also make your own sgraffito tools!
You can carve as deeply or as shallow as you like. For the pieces that have a grogged clay base, I tend to carve shallow line, trying to remove only the slip or underglaze and leaving the clay beneath in tact. Otherwise, deeper cuts on these pieces leads to rougher lines due to the grog. With smooth clay pieces, carving deeper into the clay underlying the slip or underglaze can create really interesting textures and varied surfaces.
The carving, or sgraffito, can be accomplished using a variety of tools. In my past forays into sgraffito, I primarily used a commercial sgraffito tool. The tool has a loop of wire on either end that can easily carve through the slip, and leaves a nice line. The dental tools I use for carving plaster make good sgraffito tools as well. The pen tool (mentioned in Part 1), which also works quite well, can remove a bit more clay in one pass than the loop tool. And of course you can also make your own sgraffito tools!
Using a sgraffito tool to carve lines through the underglaze to reveal the base clay of the bowl beneath.
Sgraffito generates little spirals of clay that should be periodically removed from the face of the work so they don’t interfere with the carving. Use a clean brush to sweep the carvings off the piece. Since the carvings are still moist, using your fingers or hand to remove them can smear them across the surface of your work, leaving unwanted marks.
The sgraffito is the most time-consuming part of the process. Since my designs are quite complex, it can take upwards of a couple hours to carve a small 6” bowl. I am sure some would find it tedious, but I actually enjoy the carving and find it somewhat calming and meditative.
The sgraffito is the most time-consuming part of the process. Since my designs are quite complex, it can take upwards of a couple hours to carve a small 6” bowl. I am sure some would find it tedious, but I actually enjoy the carving and find it somewhat calming and meditative.
The sgraffito process creates little spirals of clay, slip and underglaze that should be swept off the surface of the piece with a clean brush.
Step 5: Finishing
Try to carve as carefully as possible because mistakes are difficult to fully erase. If you do mess up (and I usually end up making a small mistake here or there), you can attempt to fix it. Dampen the area around the mistake and apply a bit of slip over the area that was carved inadvertently. There will be a thicker area of slip around the edges of the mistake, so I usually dip my finger in some water and attempt to smooth down the edges a bit. If all goes well, there will only be a small, almost imperceptible blemish in the final piece.
Completed sgraffito design on a greenware bowl.
After carving, I touch up any spots where the slip or underglaze may have worn thin, and the bowl or plate is allowed to dry completely before being bisque fired. I bisque fire the pieces to cone 05.
Once bisque fired, the pieces are glazed. On the bowls and plates that were coated with colored slip or underglaze, I used clear glaze. On the bowl and plate where I used a plain white slip, I actually used a colored glaze that varies in appearance depending on the color of the clay body, and shows up differently on the red clay versus the white slip. The bowls and plates were fired to cone 6 (different clays will fire to different cones).
Once bisque fired, the pieces are glazed. On the bowls and plates that were coated with colored slip or underglaze, I used clear glaze. On the bowl and plate where I used a plain white slip, I actually used a colored glaze that varies in appearance depending on the color of the clay body, and shows up differently on the red clay versus the white slip. The bowls and plates were fired to cone 6 (different clays will fire to different cones).
The Results
Square Sgraffito Plate: Smooth brown clay base with red, orange and yellow underglaze. Final clear glaze.
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Square Sgraffito Plate: Smooth brown clay base with white porcelain slip. Finished with colored glaze.
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Overall, I think all my experiments turned out well, and depending on the look of the piece I want, any of the clay bodies, slips and underglazes will work well! It is really difficult to choose which direction to take these!
- 1/4″ is a better thickness than 3/8″ for the small bowls and plates I created.
- Smooth clay may be a bit easier to sgraffito on than grogged clay, though both types of produce a nice finished product. Grogged clay wears down tools faster, but smooth clay warps and cracks more often.
- Plain slip, slip colored with mason stain and underglaze all work well as top layers for sgraffito. Underglazes are a ready-made and easily accessible option if a wide range of colors is preferred.
Sgraffito Bowl: Red grogged stoneware clay base with white stoneware slip. Finished with colored glaze.
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Sgrafito Bowl: Cream grogged stoneware clay base with burgundy and purple underglaze. Finished with clear glaze.
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Sgraffito Bowl: Smooth white clay base with porcelain slip colored with mason stain. Finished with clear glaze.
Moving Forward: Sgraffito Ornaments
For the winter season, I decided to make some ornaments using the sgraffito technique. I chose a porcelain clay for the body of the ornaments since I wanted them to be smooth and white. I used underglazes instead of slip because I wanted to create ornaments in a variety of colors, and the underglazes are ready-made and easy to use. I also don’t have to worry about fit (LINK) with the underglazes. I am pleased with the results!
Red sgraffito star ornaments.
