Draping a Soft Slab Over a Mold for a Bowl
Okay, so we've spent seven lessons on slabs joined to slabs, flat sides going to flat sides, and now we're going to do something different. We're going to take one slab and let gravity do most of the shaping for us. This is draping, and it's my favorite technique in the whole handbuilding toolkit, because it's honest work: you set it up right and the physics just cooperates.
Here's the idea. You take a soft, freshly rolled slab and lay it over the outside of something curved, a mold, a bowl, a bunched-up towel, whatever, and let it settle into that curve as it stiffens. When it's firm enough to hold its shape, you take it off the mold and you've got a bowl. No pinching, no coiling up walls, none of that. Just a slab and gravity and a little patience.
What you need for a mold
You do not need to buy a set of plaster hump molds, though studios sell them and they work great. For your first one at home, use what you've got:
- An upside-down mixing bowl, ideally one with some visible curve, not perfectly hemispherical
- A colander, if you don't mind the texture it leaves (I actually like this one)
- A wadded-up towel draped over a bowl if you want something less regular
Whatever you use, cover it. Plastic wrap smoothed over the mold, or if you're me, one of those Costco shower caps stretched over the top. Clay sticks to bare ceramic and to most fabric, and you will not enjoy prying a stuck slab off a good mixing bowl. Cover it first, every time.
Rolling and draping
Roll your slab the way we've practiced, evenly, somewhere around a quarter inch for a small bowl, and don't skip the resting and covering steps between rolling and draping. You want this slab soft and flexible, softer than what we've used for straight-sided boxes, because it needs to bend without cracking.
Lay the slab over your covered mold, centered, and gently press it down from the middle outward. Use your palms, not your fingertips, so you don't leave dents. You're coaxing the clay to follow the curve, not forcing it. If you get folds or pleats forming at the edges, that's the clay telling you it's got extra material trying to go somewhere it can't. Cut a small dart, a little wedge shape, out of the excess, and smooth the two cut edges back together with a bit of score and slip. Yes, score and slip even here, even on a dart this small. I don't make exceptions for small joins. I've watched enough of them crack in the kiln to know the rule doesn't care how minor the join looks.
Once it's settled and smooth, trim the rim with your needle tool while it's still on the mold, following the edge of the mold or free-handing a shape you like. This is much easier to do now than after you've pulled it off.
Letting it set up
Leave the bowl on the mold, uncovered this time, until it's firm enough to hold its shape on its own, which usually takes a few hours depending on the room and how thick you rolled it. This is one of the only times I tell you not to cover something, because you actually want some of the moisture leaving the outer surface so it stiffens against the mold. Check it every so often. You're looking for leather hard, firm enough that it won't sag when you lift it, still cool and slightly damp to the touch.
Pull it off the mold too early and it slumps. Too late and it can crack as it shrinks against a surface it can no longer move on, especially at the rim if it's gripping the mold's edge. This is exactly the kind of shrinkage crack we talked about a couple lessons back. Check on it, don't just set a timer and walk away.
I made a bowl like this at two in the morning last year, home with a newborn, too wired from the feeding to go back to sleep and needing my hands to do something that wasn't holding a baby. I draped a slab over a mixing bowl at my kitchen table with one lamp on, and it is, honestly, not a good bowl. The rim's uneven, I trimmed it half-asleep, and I pulled it off the mold too soon in one spot so there's a soft dip on one side. I love it anyway. It's not a piece I'd tell you to copy, technically, but it's proof that the technique works even when you're not at your best, which is maybe the whole point of a method that lets gravity carry some of the load.
Don't chase symmetry here, either. An irregular, slightly lopsided draped bowl usually has more character than one that came out perfectly even. Fix cracks. Leave the personality alone.
Before next time
Pick a mold from your own kitchen, something you already have, and get a slab draped and settling before our next session. Check on it more than once. That's really the whole assignment.
~erin