Etched in Clay: How to Make Beautiful Relief Surfaces with Shellac Resist

A water-abraded surface of calligraphic lines decorates the surface of Jim Gottuso’s clean-lined forms.

A water-abraded surface of calligraphic lines decorates the surface of Jim Gottuso’s clean-lined forms.

Not long into his ceramics career, Jim Gottuso became enamored with the idea of using wax resist for surface decoration. The only problem was the wax resist didn’t do well with delicate decoration or thin brushwork. On both greenware and bisqueware, the wax just became a goopy mess.

So Jim experimented and explored, all the while building his own aesthetic, and discovered the resist medium that could give him what he wanted: shellac. Today, Jim explains how he uses shellac resist and hydro-abrasion to create his intricately patterned surfaces. – Jennifer Harnetty, editor.


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About five years ago, I decided to embark on a ceramics career and before long developed an interest in trying to exploit the use of wax resist in the service of surface decoration. I was disappointed with the waxes I tried on both bisqueware and greenware. They were globs of goo that didn’t respond to thin brushes or delicate application.

At the same time I happened upon the work of Arne Ase whose work absolutely floored me, especially after unsuccessfully trying wax, paraffin, and acrylic medium on greenware in an attempt to etch the unprotected areas and create depth to the surface. His decorations were incredibly delicate and, of course, his use of soluble salts and translucent porcelain came together in pieces of sublime beauty. What wasn’t clear was what he used for a resist. It turns out that Arne had written Water Colour On Porcelain, which has been described as the definitive book on soluble salt use and the secret ingredient had to be in that book. Unfortunately it is out of print, but the library managed to find a copy, and the book revealed the ingredient as shellac.

I’ve since been told by fellow blogger, Michael Kline, that at Penland the process of using a resist and dissolving the exposed unfired clay was referred to as hydro-abrasion. This sounds a bit scientific to me but in the absence of a concise alternative it might very well be the best name for it.

After a couple of years of hydro-abrasion trial-and-error as well as nurturing the evolution of a personal visual vocabulary, it turns out that this process dovetails very nicely with what appeals to my sense of design, form, and aesthetics. For many years I’ve been attracted to certain drawing, painting, and calligraphic styles, and usually cite artists like Cy Twombly and Mark Tobey as influences, along with my perception of Jung’s automatic writing. But after many years of not really caring about the origins of influence, I’ve come to believe that I’ve always just been in love with what happens when a brush, pen or pencil makes contact with another surface. Using shellac as a resist on dried, unfired clay allows the surface to be etched without losing the immediacy and spontaneity of such brushwork.

<p>Fig.1 Apply resist to both the foot and rim to preserve their integrity throughout the process.</p>

Fig.1 Apply resist to both the foot and rim to preserve their integrity throughout the process.

Fig.2 Apply the first (and ultimately foreground) layer of resist for your chosen design.

Fig.2 Apply the first (and ultimately foreground) layer of resist for your chosen design.

Fig.3 Allow the shellac to completely dry and remove clay from the exposed areas using a damp sponge.

Fig.3 Allow the shellac to completely dry and remove clay from the exposed areas using a damp sponge.

 

Thinking in Reverse

Begin with a bone dry, completely trimmed piece, in this case a bowl. Since my pieces are typically about 1/4-inch thick, tapering to 3/16-inch at the rim, I take extra care not to put a strain on it. This process requires a bit of thinking in reverse. Protect the parts of the piece that are not to be altered. The first layer of shellac resist applied to the piece, because it covers the clay before any abrasion takes place, end up being the topmost layer, or highest relief area at the end of the process. Since I don’t want the rim or foot to be etched, I apply resist to both to preserve their integrity throughout the process (figure 1).

Defining the Foreground

The next step is to apply the first layer of resist that will create the decoration and will result in the top or foreground layer of the final design (figure 2). One way to think about this would be to imagine writing your name with the shellac then etching the un-shellacked areas. If, after that another layer of shellac was applied in a grid pattern over the name and etched again, the result would appear as your name hovering over the grid, even though the applications were done in reverse. Although this seems counter-intuitive, it becomes clear with repetition. For the finished piece shown here, the first layer is a series of vertical calligraphic marks that go from the foot to the rim.

Abrading the Clay

After allowing the shellac to dry completely (24 hours will do), you’re ready to abrade the exposed areas with a damp sponge (figure 3). If you intend to preserve what’s been laid down in shellac without degradation, you might want to jettison the idea of abrasion, think of the your goal in the process as more like dissolving the clay, even though that’s not technically what’s happening.  The abrasion occurs when the water between the sponge and the surface of the pot collects dislodged clay particles in it and creates a localized slurry, which will get thicker and thicker as you go. Leaving this thick slurry between the sponge and the pot is not good for your shellac image. When the sponge has lots of clay on the surface and little water left in it, you’re likely to simply eradicate your image along with the unprotected areas as the large particles on the sponge repeatedly move across and scratch into the surface.  To avoid this, load a sponge with water and wipe the surface of the pot until the slurry starts to form, then rinse the sponge thoroughly in your bucket of water and repeat. In this early stage, with large unprotected areas of clay, this means you’re having to rinse out the sponge frequently, sometimes after only two swipes across the clay.

Fig.4 Apply shellac over the top of the first layer, making this second layer extend about 1/8 inch past the edge.

Fig.4 Apply shellac over the top of the first layer, making this second layer extend about 1/8 inch past the edge.

Fig.5 Brush shellac in the remaining unprotected areas, leaving only a small gap between the two covered areas.

Fig.5 Brush shellac in the remaining unprotected areas, leaving only a small gap between the two covered areas.

Fig.6 Allow the piece to dry again and repeat the etching process. Continue these steps until you are satisfied.

Fig.6 Allow the piece to dry again and repeat the etching process. Continue these steps until you are satisfied.

 

Defining the Middle Ground

After allowing the piece to completely dry again apply a second layer of shellac. I’m trying to create the appearance on the final bowl of a thin brush stroke that’s hovering or sitting on top of another, slightly wider, brush stroke. I apply shellac over the top of the original shellac lines and make this second layer extend about 1/8 inch past the edge of that first layer (figure 4).

Adding Linear Elements

On this particular bowl, my goal is to have a linear reinforcement of the negative space that’s created by the slightly widening brushwork. To achieve this, shellac is also applied in all the remaining unprotected areas, leaving only a small (1/8–3/16 inch) gap of bare clay between the two covered areas (figure 5).  Allow the piece to dry again and repeat the etching process (figure 6). Since more (or even most) of the surface is covered by shellac at this point, you don’t have to thoroughly rinse the sponge out quite as frequently. When you notice a slurry developing, rinse the sponge to avoid abrading the edges of the resisted areas, otherwise your lines may have jagged rather than crisp edges. Since the area being dissolved now is linear as opposed to large planes, moving in a circular motion with the sponge aids in getting a uniform depth to the etching. It can be particularly difficult to gauge how deep the etching is now because the layers of shellac have some thickness or depth themselves. The shellac will eventually burn out in the bisque and only then is the depth and uniformity of the etching revealed.

Fig.7 Brush a black slip that is suitable for use on greenware over the entire surface of the outside of the bowl.

Fig.7 Brush a black slip that is suitable for use on greenware over the entire surface of the outside of the bowl.

Fig.8 Use a sponge to wipe off any black slip that is not in the etched lines.

Fig.8 Use a sponge to wipe off any black slip that is not in the etched lines.

Fig.9 Go over the entire surface with a stiff brush after the bisque firing to clean off the shellac residue.

Fig.9 Go over the entire surface with a stiff brush after the bisque firing to clean off the shellac residue.

 

Adding Color

Let the piece dry completely then brush a black slip suitable for use on greenware over the entire exterior of the bowl (figure 7). My black slip is made from throwing slip reclaim and 35 grams of Mason stain #6600 black added per 2 cups of slip.  With a sponge, wipe off any slip that is not in between the etched lines before it dries (figure 8). Remember that if you accidentally take too much slip off and there are unprotected areas that are now back to bare clay, it’s relatively easy to reapply more slip immediately to that area and try again allow it to dry, then bisque fire.

Glazing Strategies

When the bowl is bisque fired, you’ll finally be able to see how the decoration looks, from the subtleties of the etched layers to the contrast between the dark and light tones of the slipped and bare areas. At this point, a flaky residue may be present everywhere the shellac was applied, depending on the thickness of the shellac layers. This wreaks havoc with glaze application, so brushing the entire surface with a stiff brush is necessary to clean it up (figure 9).  When glazing, I dip my pots but spraying, pouring and painting the glaze also works. Of course, in order to accentuate the subtle differences in relief, transparent or translucent glazes, or glazes that break over texture and edges, works the best. If the colored slip is dark (like this black one), a darker glaze cuts way down on the contrast. Note: Since the relief is low, a thin glaze application works better since a thicker glaze on the finished piece will soften the etched effect.


 

Materials

  • Shellac
  • Denatured alcohol
  • Brush
  • Sponge
  • Water
  • OSHA approved respirator

Shellac thickens when exposed to air and will lose its ability to soak into the clay body thoroughly. It can be thinned with alcohol but over time it will lose its viscosity and will eventually need to be discarded. Avoid the waste by decanting only what you need into a small lidded jar for application.


Jim Gottuso lives and works in Louisville, Kentucky. To see more of his work, check out his blog, http://jimgottuso.wordpress.com/ and his Etsy site, http://gottuso.etsy.com/.


 

**First published in 2012
Comments
  • Since it is carried in alcohol, shellac is an ideal material for this….it penetrates the clay just enough to stick, and because it’s a natural resin (made from the lac beetle) it will burn away in bisque without nasty fumes or residue. Shellac is also used to seal the plaster ‘masters’ for mold-making, and to retard deterioration of wooden bats.

    I have used a similar technique with brushwork using balloon rubber (liquid latex) followed by gentle sandblasting. A more radical amount of relief is possible for larger work, there’s no need for re-wetting the surface, and the dried latex can be peeled off afterwards, if necessary for further decorating. it’s like the “liquid frisket” used by airbrush artists. Brushes are cleaned with ammonia.

  • Hi I live in argentina, and am not sure what shellac is, can it be substituted by soem3thing, or what are its components. Tnaks, thanks for the post, very interesting, and want to try it!

  • hi,
    ellyn, i don’t think you need to worry about the fumes from firing pots with shellac nearly as much as you need to be concerned about the fumes from bisqueing and glazing the pots. there is a lot of harmful off-gassing during a bisque and the kiln has to be vented. an example of how powerful these gases are is that my metal vent tubing has been eaten all the way through and this would have happened regardless of using shellac or not. good luck with process.

    holly, the fumes from applying the shellac are potentially harmful. i’m confident that if you have a respirator and ventilation and you are not doing what i’m doing (8 or more hours a day for a period of weeks) and are only doing small sessions, that you will be fine.

    lynette, i don’t know what they’d call it in south africa but i’m almost sure they have it there. it would be in the paint section of a hardware store. it’s made from the secretions of a lac bug.

    laura, the shellac is denatured alcohol based.

  • Hello, nice you posted this, I have just start trying to make my first porcelain cups using shellac to make this water erosion process. I learned this technique from my Portuguese ceramicist friend Helena Brizido who makes beautiful porcelain objects using shellac. I live in Sweden and I found the shellac in an artist store, they didn’t have it in the pottery supply shop. You say that one should let the shellac dry for 24 hrs. but mine dries quite fast, after about 1/2 hour is dry, but I suppose this is because I have only made quite small cups and not big pieces. In my school we have an electric kiln and the teacher said it was no problem as the shellac just burns out. I haven’t seeing the results yet (only this Saturday) so I am quite excited to see what comes out of this experience.

  • For those who live in Argentina : Shellac is Goma laca.(its solvent is alcohol)
    From Wikipedia:Lac is the scarlet resinous secretion of a number of species of insects. Seedlac which still contains 3-5% impurities is processed into shellac by heat treatment or solvent extraction.

  • We have used shellac in painting classes but used methylated spirits to dissolve it in and to thin it. Will this work exactly the same as alcohol?

  • I have tried this process with limited success.The problem I encountered was when removing the clay with a sponge or soft brush the edges of the shellaced design chipped away . This left a rough rather than smooth edge to the design. Any ideas on how to remedy this problem?

  • I have tried this process with limited success. The problem I encountered was when I removed clay with a sponge or soft brush the edge of the shellaced design chipped away. This left the design with a rough rather than smooth edge. Any ideas on how to remedy this?

  • Mr. Jim i am Hassan Kashigar, i want to used this technique in my university, will share this technique with my students , i need your help regarding this Technique

  • Hi- Love the info. Thanks. I’ve imprinted some leaves into clay tile. Let it dry. Now going to apply shellac and let it dry. Then try removing the background with a damp sponge. Will let you know how it works out.

  • Last week, my pottery instructor, Janna Burford, showed me a similar technique. I had pressed a lupin leaf into clay and holding the leaf in place, she wiped away the surrounding clay. The effect was a beautifully clear embossed leaf. No shellac required! It isn’t fired yet. can’t wait to experiment further!

  • Thanks for the great idea of sellack! It works perfectly if you select the sponge carefully (I think it is a key thing the pick the right one) and patiently wait between the wipes.
    As for sellack, my experience is that it requires denaturated alcohol ( alcohol content above 94%) otherwise it will not be soluble.

  • The shellac is a resin. In spanish is goma laca and is used as a varnish for polishing furniture. If you do not have shellac you can use the medium matt gel that you use with the acrilc paint. It also burns during the fire. The schellac dries quite fast I never wait 24hrs and you can do it slowly and wait for the clay to dry while you are doing the water erosion. You can by the schellac already made at art stores and so the medium matt. Hope I helped.

  • Hi Jim,

    Loving your work! This is an excellent article, and very interesting to see your approach to hydro abrasion (or water-etching, as I call it). I am a potter based in Scotland, and have used this technique since about 1998 to create highly translucent porcelain pieces (www.theweeviking.com). There are not a lot of potters around using this technique, and it’s lovely to see someone who is using basically the same technique and materials, but getting a completely different (and absolutely stunning) effect. Love the use of slip to highlight the edges of the relief pattern.

    Cathrine Holtet

  • Neither – it’s ethanol based. Don’t try to use rubbing (Isopropyl) alcohol. Any good hardware store has denatured ethanol – it’s poisoned so if you try to drink it you throw up. Get the strongest conc. they offer. If they sell shellac but don’t carry ethanol bring this to the attention of the manager. No, you can’t use vodka – 200 proof is only equal to 50% and that’s too diluted for Shellac, sorry.

    Shellac is actually made from dissolving a species of beetle’s carapaces in ethanol. WTF? Who discovered you could do this? It’s a testament to humanitie’s inventiveness. LOL!

  • Do you prefer it? It is more viscous than shellac but that could be a good thing depending on the patterns you’re doing.

  • Hi Jim,
    I love your work also..

    I was able to get French polish from the hardware which is a combination of shellac and methylated spirits. Will this work?

    Catherine

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