Slip-Slab Construction: Bone Dry Building

by Bryan Hopkins

In an update to a previous piece I wrote about slip cast slabs:

Here are some images of completed pieces using the slip cast slabs.

Bryan Hopkins
Bryan Hopkins

As you can see, they are translucent- more so than any work I have ever produced. The above pieces are my cone 10/11 porcelain, fired in a gas kiln, reduction atmosphere. These are not the low-fire porcelain I have written about previously.

There is a reason why I am continuing firing to cone 10: surface. Although the low fire porcelain is just as, if not more, translucent than the cone 10 clay, the issue for me is the surface as it relates to portraying the idea, and physicallity, of wood. The low fire has a sheen to it that does not work well for these types of pieces- it is too glossy. Even when a little matt, it is still too reflective of ambient light to truly be a trompe l’oiel surface. The cone 10 clay has little if any reflective quality, thus producing shadow detail with a minimum of lighting.

This update is to tell you about a new process (to me) of construction- bone dry slab construction. Although I have heard of artists using paper clay when bone dry, it has never been utilized as a true construction technique, but rather is a way to repair a piece, and a last resort.

What I have been doing is simple, and only works with very thin bone dry slabs, about 2mm thin or less.

In learning how to build with such thin slabs. like the piece above, I encountered small cracks around areas of tight curves. So I instinctively took a small piece of bone dry, cast off textured slab, painted some slip on the the back, and stuck it over the crack. This worked. No magic this or paper that- just the slip I use every day.

So I thought- well, if the patch works, how about a whole piece?

This is what I have arrived at: I pour out my slabs, wait to firm up, then press them in to the bisque molds to apply texture. (If you are lost, please check out a previous posting I did on slip-slabs). The slabs are then cut in to planks of arbitrary lengths and widths, then left to dry, which takes about an hour.

Bryan Hopkins

If I want to put a curved piece in I just cut it to the correct length, add the curve, then let that dry with the rest of the pieces. In the case of the piece here I drilled it out when just beyond leather hard.

The slabs are attached using a bead of casting slip on one of the surfaces.

Bryan Hopkins

When put together, the oozing stuff is cleaned up on the outside, but left on the inside. I like the way it looks inside for some reason. As you can see, the slip reactivates the clay slab enough to allow a good bond, but not enough to warp it.

Bryan Hopkins

Once finished, the piece can go immediately in to the kiln.

Bryan Hopkins

If I use a glaze on any section it must go through a biscuit firing, otherwise it is single fired to cone 10/11 in a gas kiln, reduction atmosphere.

In my typical slab construction, pieces might not warp until they go through the cone 10 firing, and when they warp enough they are destroyed. This dry method seems to resist warping, and I am throwing less away.

Maybe worth trying?