Plaster and ceramics go hand in hand. We ceramic artists use plaster for everything from drying or wedging surfaces to stamps or molds for slip casting. But potter Lauren Sandler has been making hump molds for her work out of unfired clay. This way she doesn't have to deal with the mess of plaster, doesn't have to wait for her molds to dry and be fired, plus, if she gets tired of the form, she can reclaim the clay for some other use. Now, I don't mean to diss our good friend plaster, but I do love the simplicity, speed, and versatility of this method. Check it out and see if you agree! - Jennifer Harnetty, editor.
Why Use Plaster for Molds, When You Can Use Unfired Clay?
by Lauren Sandler
Bowl forms are particularly interesting for decorating because they provide an expansive landscape to explore. A generous open object when functioning, a bowl acts as an offering yet also as an object of containment-a reservoir of reverie and reflection. It's this paradox of offering and containment that I find most alluring and attempt to expand upon with my surface work.
In his technique-packed DVD, Ben Carter shares his methods for integrating surface design with altered wheel-thrown and handbuilt pottery. Referencing pillows, tufted furniture, and quilts, Carter imbues his pots with softness in a variety of ways—from altering freshly thrown pots to create volume, to stretching soft clay into foam slump molds.
Making the Mold
Begin by making a clay mold that will be used to drape a slab over. The mold will be used to make the bottom quarter of the final bowl form that will then be built up to the finished shape and height with coils. The mold is made upside down and solid-later it will be turned upright and hollowed out. I start by drawing a boundary line to follow by first cutting out a paper pattern for what will be the top of the mold (when upright) and outlining that on the bat (figure 1).
I begin the mold with a large thick slab, cut around the drawn line then add and remove clay as needed to create the desired form (figure 2). Take your time in shaping the mold; even out and smooth the surface with a Surform tool or rasp, then refine the shape and the surface with metal and rubber ribs. Place a bat and a torpedo level on top of the form and make any adjustments needed until it is level (figure 3). Once the mold has set up to a firm leather hard (wet enough to hollow out, but firm enough to hold its shape when handled) turn it upright and examine it. Check the shape to assure that the shape is what you're looking for and add or remove clay as needed.
Using the Mold
Preparing and Adding Coils
Finishing the Rim
Once you have the desired height and volume, even out the rim with a Surform, then measure and mark the four corners of the rim using a string and ruler. Decide how much of a curve you would like and mark the lowest point on two opposite sides of the rim. Use the Surform to cut the clay away moving from one side to the other (figure 10) to maintain the same amount of pressure.
Once you have the curve defined, smooth the rim using your fingers or a rib. (figure 11).
For more information or to see more of Lauren Sandler's work, please visit www.laurensandlerstudio.com.
For great mold making techniques, be sure to download your free copy of Ceramic Mold Making Techniques: Tips for Making Plaster Molds and Slip Casting Clay, Volume II.