Press-Molded Bowls

On the occasion of our wedding, my husband and I received a beautiful set of stoneware dishes (above, photo by M. McWhorter) that were slab-built by my dad. However, we are in need of matching or coordinating bowls so we can finally dispose of my husband's ugly college set. The construction of a bowl is not so easily accomplished using slabs, in the traditional sense. But taking pieces of a slab and pressing them into a lined mold, creating a patchwork that is then painstakingly smoothed, is a simple, strong method that still creates a vessel with hand-built characteristics (unlike the relative perfection of a skillfully wheel-thrown bowl). I'm hoping they'll blend into the feel our dishes have. I will, of course, glaze them similarly.

I don't have a home ceramics studio. We currently rent and even if we did own we would probably need an outbuilding to store ceramics equipment, particularly a kiln, in order to keep our homeowner's insurance at a reasonable rate. A kiln would also require some beefed-up electrical wiring. However, I don't live far from Indian Hills Community College, which has a very well-developed ceramics program. Let's say I have ties to the faculty and am most fortunately welcome to work there. So I began manufacturing the pieces I'm planning last Friday. Let me take you through the process. It's simple but time-consuming, much more time-consuming than throwing but the end results are so pleasantly rustic that they are occasionally worth the effort.

Here's the stoneware that's manufactured at IHCC (it's a cone 6 blend with a pretty iron color):

I grab two hunks: one to roll out in a slab (the larger), the other for the coil (the smaller) which will become the rim of my bowl. It's important to have them exposed to air in the same manner (meaning the same length of time). One of the biggest problems one fights in hand-built ceramics is having areas of uneven moisture in a form. It's one of the best ways to ensure that the piece will crack while drying.

Happily, IHCC is equipped with a slab-roller. Creating slabs otherwise takes some finesse and a canvas-coated table. The slab-roller also affords a few more options when it comes to texturing the clay.

Here I am using a piece of three-dimensional ceiling paper that when painted is meant to simulate the look of tin or copper ceilings. It is actually the covering on the ceiling of my bedroom at my parents' house. My dad also used this when creating my dishes so I am attempting to create a greater degree of continuity between the two sets. I've rolled out the slab first on canvas and then flipped it onto the section of paper I'm using and rolled it again to transfer the texture. I'll then transfer this to my work area and cover it and my hunk of coiling clay with plastic (non-breathable) to retain moisture while working.

Tools I'll be using. Yes, in my opinion Diet Coke is essential!!

I've lined the bowl that serves as my mold with plastic from the dry cleaner's and have begun ripping pieces off of the slab and conforming it to the contours of the mold. I'm being careful to overlap the pieces and I'm mushing the seams together.

The mold has been covered and I have worked and mushed the seams so that I have a relatively even thickness throughout my walls.

Now I'll use this simple metal rib to begin smoothing the inner walls. This requires a gentle hand as an overly aggressive one will result in some serious gouges to the clay.

I've done as much with the rib as I can.

Now I'll use this dry round sponge (repeat: DRY!!! Never use a wet sponge for this or be prepared for hairline cracks) to continue smoothing the inside. I also use my fingers a little on stubborn spots. Don't add clay to low-lying areas because you will risk trapping air. This will cause a miniature explosion of super-heated moist air in the firing process and you'll be left with an unsightly pock-mark on the surface of your piece.

Looking good!

Now I'll use my fettling knife to remove the excess material from the rim of my bowl.

At this point I'll roll out the coil for my rim. I would under most circumstances not recommend considering the bowl finished without adding this rim. It will be very weak and worse: it will be both unsightly and razor-sharp when glaze-fired. There are enough badly-made items in the world without your skipping these next few steps and creating more of them. Roll a long coil of even thickness that is not too thin. A lot of the bulk of the coil with be lost while joining it to the bowl.

Score and slip (liquid clay--I prefer mine the consistency of glue) the points of contact between the bowl and its coil rim. If you don't it will simply crack off of the pot not much later.

Add the coil. I have also added a small coil at the joint between the ends of the coil rim and begun to blend it in. Another way to deal with the joint attractively would be to roll a tiny coil, flatten it and adhere it over the joint (by scoring and slipping it into place) and just blending the ends of the little coil into the bowl. This is perhaps a more "honest" way of dealing with the joint as it reveals more about the process of creation than my tendency to blend it away. On my own pieces, however, I find that it is a distraction.

I've begun to pull clay from the coil down into the body of the bowl to blend the two. I'm trying to be maintain a straight line across the coil so that the blending process will not result in an uneven-looking rim.

Now it's time to go back in with the metal rib, dry sponge, and my fingers to create a smooth finish.

Mission accomplished.

When it has had a little time to set up (this piece, because its form describes a dome and can be trusted to hold itself up, needed very little time to set up--I really just gave it enough time to feel satisfied that I wasn't going to flatten out the coil rim), take a bat (a flat surface--nowadays it's usually a disk of plastic), cover with a paper towel and flip your bowl upside down on top of it. Carefully remove the mold. Even more carefully remove the plastic lining covering your piece. Examine the outside of the rim. It will probably need to have its transition to the bowl smoothed a bit since you haven't been able to access that part of the piece while it was still in the mold. I like to use the blunt point of my fettling knife and smooth a shallow line at the transition point. It emphasizes the rim and deals with the problem without disturbing the texture of the surrounding areas. (As a side note: the texture from the ceiling paper was unfortunately too shallow to remain visible after the molding process. What little was retained will almost certainly be obliterated when I glaze it. However, the plastic lining always imparts a deep, random texture which will be sure to pick up.)

At this point I'd just dry it for a while upside-down. This keeps the rim from drying at a pace more accelerated than the rest of the form (which would result in cracking). Once it's leather-hard, I'd flip it over until it's completely bone dry, at which point it will be ready for bisque firing. I'll describe this and firing terms later when my bowls are going through the process. In the meantime...

Here are some bisque-fired press-molds my dad made. You can see the other type of joint I was describing above.

And this is a glaze-fired press-mold by my dad.

You may be able to see from these last two images that I tend to smooth the interiors of my press-molds out a lot more than my dad. Obviously, then, it's just a matter of taste in one's own work, not of necessity.

Until next time...