Intriguing and unpredictable patterns emerge when you incise and stretch a clay slab that’s covered with colored slip. I first stumbled across this phenomenon years ago when I rolled out a slip-coated slab that had a couple of errant nicks in the surface, and as the slab got thinner I noticed how those cuts widened and became quite graphic. You never know quite how it’s going to look in the end, and that’s what attracts me to it.
Cutting Even Slabs
I cut thick slabs from the clay block with a homemade slicer I call a harp (1). The U-shape is ⅛- × ¾-inch (0.8- × 19-mm) steel that has enough spring in it to hold a wire taut. To make it more comfortable to grip, I slip an 8-inch-long section of garden hose onto the bar before I make the bends (2). The wire is attached ½ inch (12.7 mm) from the ends of the steel bar, so the slab it cuts is ½ inch (12.7 mm) thick (3).
The slabs usually start out about a ½-inch thick before they’re stretched, and end up between 1/32 and 3/32 inch thick after. Yes, that’s quite thin, and yes, that can cause problems like warping and cracking, but I accept the rate of loss because I like the way a thin slab responds to how I’m working with it.
Pigment and Slip
I use both a white stoneware, shown here, and a brown stoneware, shown in the trays and teapot at the end of the article. The white clay provides a striking contrast to a black or dark blue slip (I don’t use a glaze over it), and the brown clay picks up the turquoise glaze I apply over the black slip decoration.
The black slip is a mix of oxides (see recipe) and works at any temperature. A black Mason stain works okay, too, but I think the oxides look richer.
Prepping the Slab
Coat a ½-inch (1.2-cm)-thick slab with pigmented slip and wait a few minutes for the surface sheen to dull (4). You want a pretty thick coat. I mix my slips to about yogurt consistency— thick enough to stand a brush up in it. Waiting for the sheen to dull tells me the slab has pulled much of the slip’s moisture so it’s less likely to smear. The slab is fresh, but slightly stiff will also work. I’ve tried using underglazes in place of slips, but they take a long time to lose their moisture on damp clay.
Just Scratching the Surface
Begin making repeated scratch marks into the surface of the pigmented slip (5). A very light touch is all you need to cut through the layer of slip into the clay below. Make scratch marks in repeated rows from top to bottom, left to right, edge to edge. Experiment with your own variations. My marks are at a slight angle to encourage a particular pattern once I start stretching the clay.
Any tool with lots of sharp points will work here: a fork, a saw blade, even a bundle of pine needles. I’ve made several scoring tools (A) by laminating used X-Acto (or similar) blades between thin strips of wood veneer, then gluing it all together (B).
Throwing—No, Not That Kind
Stretching the slab separates the barely visible scratches in the black slip, revealing the white clay beneath. The two ways to stretch a slab are the slap and the roll; for this, I combine the two methods.
The slap involves hurling the slab at an angle across a work surface (6, 7) or the floor, so that the momentum of one end of the slab elongates it slightly. (Here’s where the term “throwing” is literal.)
As you continue to slap the clay out on your worktable, the scratch marks will progressively open up (8, 9), allowing the clay beneath the slip to start showing through—this is where the contrast between slip and clay works well. The more you throw, the more a pattern or contrasting lines emerge (10, 11).
The slab toss leaves the slab thinner in the middle than the edges, so once the lines have opened up, use a rolling pin to flatten the slab and, in effect, inlay the slip into the slab surface (12). Now you have a prepared slab with a printed pattern and are ready to start building.
Hayne Bayless is a studio potter in Ivoryton, Connecticut. In college he managed to avoid any academic involvement with clay, ending up instead with a degree in journalism. In 1992, after ten years working a perfectly good job at a newspaper, he quit to make pots. He abandoned the potter’s wheel early on, finding greater freedom in handbuilding.
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Intriguing and unpredictable patterns emerge when you incise and stretch a clay slab that’s covered with colored slip. I first stumbled across this phenomenon years ago when I rolled out a slip-coated slab that had a couple of errant nicks in the surface, and as the slab got thinner I noticed how those cuts widened and became quite graphic. You never know quite how it’s going to look in the end, and that’s what attracts me to it.
Cutting Even Slabs
I cut thick slabs from the clay block with a homemade slicer I call a harp (1). The U-shape is ⅛- × ¾-inch (0.8- × 19-mm) steel that has enough spring in it to hold a wire taut. To make it more comfortable to grip, I slip an 8-inch-long section of garden hose onto the bar before I make the bends (2). The wire is attached ½ inch (12.7 mm) from the ends of the steel bar, so the slab it cuts is ½ inch (12.7 mm) thick (3).
The slabs usually start out about a ½-inch thick before they’re stretched, and end up between 1/32 and 3/32 inch thick after. Yes, that’s quite thin, and yes, that can cause problems like warping and cracking, but I accept the rate of loss because I like the way a thin slab responds to how I’m working with it.
Pigment and Slip
I use both a white stoneware, shown here, and a brown stoneware, shown in the trays and teapot at the end of the article. The white clay provides a striking contrast to a black or dark blue slip (I don’t use a glaze over it), and the brown clay picks up the turquoise glaze I apply over the black slip decoration.
The black slip is a mix of oxides (see recipe) and works at any temperature. A black Mason stain works okay, too, but I think the oxides look richer.
Prepping the Slab
Coat a ½-inch (1.2-cm)-thick slab with pigmented slip and wait a few minutes for the surface sheen to dull (4). You want a pretty thick coat. I mix my slips to about yogurt consistency— thick enough to stand a brush up in it. Waiting for the sheen to dull tells me the slab has pulled much of the slip’s moisture so it’s less likely to smear. The slab is fresh, but slightly stiff will also work. I’ve tried using underglazes in place of slips, but they take a long time to lose their moisture on damp clay.
Just Scratching the Surface
Begin making repeated scratch marks into the surface of the pigmented slip (5). A very light touch is all you need to cut through the layer of slip into the clay below. Make scratch marks in repeated rows from top to bottom, left to right, edge to edge. Experiment with your own variations. My marks are at a slight angle to encourage a particular pattern once I start stretching the clay.
Any tool with lots of sharp points will work here: a fork, a saw blade, even a bundle of pine needles. I’ve made several scoring tools (A) by laminating used X-Acto (or similar) blades between thin strips of wood veneer, then gluing it all together (B).
Throwing—No, Not That Kind
Stretching the slab separates the barely visible scratches in the black slip, revealing the white clay beneath. The two ways to stretch a slab are the slap and the roll; for this, I combine the two methods.
The slap involves hurling the slab at an angle across a work surface (6, 7) or the floor, so that the momentum of one end of the slab elongates it slightly. (Here’s where the term “throwing” is literal.)
As you continue to slap the clay out on your worktable, the scratch marks will progressively open up (8, 9), allowing the clay beneath the slip to start showing through—this is where the contrast between slip and clay works well. The more you throw, the more a pattern or contrasting lines emerge (10, 11).
The slab toss leaves the slab thinner in the middle than the edges, so once the lines have opened up, use a rolling pin to flatten the slab and, in effect, inlay the slip into the slab surface (12). Now you have a prepared slab with a printed pattern and are ready to start building.
Hayne Bayless is a studio potter in Ivoryton, Connecticut. In college he managed to avoid any academic involvement with clay, ending up instead with a degree in journalism. In 1992, after ten years working a perfectly good job at a newspaper, he quit to make pots. He abandoned the potter’s wheel early on, finding greater freedom in handbuilding.
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