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Making an Impression

Posted By harsha sr On May 6, 2011 @ 12:40 pm In College Level Ceramics Assignments,Education,Lesson Plans 6-8,Lesson Plans 9-12,Pottery Making Illustrated | 1 Comment

This project will help you

  •  Create clay stamps and use found objects as stamps
  • Learn about slump/hump molds
  • Learn about creating a bisque mold
  • Create multiples of a form using low tech methods
  • Incorporate raised design elements into your work

 

 

Tools:

  • bisque or plaster stamps of your own design to create impressed patterns on the slab
  • bisque drape mold created from an interesting shape or from your own design
  • clay slab bisque mold with impressed designs (made during the process)
  • mold release agent (cooking spray or vaseline)
  • pony roller to thin and smooth slab edges and form clay over the mold
  • ribbon or loop carving tools
  • fettling knife
  • banding wheel (optional)

 


Download a printer-friendly version of this assignment here:

Making an Impression


The way that clay stamps can activate and transform the clay surface has been a constant source of fascination to me, helping my work evolve and grow over the last 35 years. I’ve worked with traditional, impressed designs, and more recently with raised designs created via a two-step process.

 

The platters with raised patterns are created using a hump mold and slab construction. First a pattern is stamped into a slab that’s been draped over a form, then this slab is dried and bisqued to create the mold.

 

The surface designs on the mold create a convex, or raised pattern rather than the typical concave surface achieved with stamps. I came up with this idea a few years ago after becoming frustrated with the way traditional stamped patterns did not hold up when using drape molds. I wanted to make utilitarian forms that were elegant, had fine detail and could be reproduced. It was also essential to me that making these pieces kept my joy for working with clay alive!

 

Finding Mold Forms

 

There are never-ending sources of forms all around us to use as a base shape from which we later make this convex clay mold. The outside of plastic or metal mixing bowls, and even a solid mound of clay that’s been centered on the wheel and shaped into a low, gradually curved solid mound and dried to the leather-hard state will work.

 

The form must function as an exterior drape or hump mold. If you find an interior shape you like, simply make a plaster mold using #1 Pottery Plaster. Be sure to spray the interior of the form with cooking spray or coat with Vaseline as a release agent, then pour the plaster inside the form. Remember that plaster expands slightly as it hardens, so it’s best to avoid making a mold of anything too fragile.

 

To make large platter molds, I first create a plaster mold using a Slump Hump form, which is a plastic mold form that can create both slump molds and hump molds. Slump Hump forms are available in a variety of shapes and sizes at ceramic supply companies.

 

Making the Clay Bisque Mold
Once you’ve found or made a drape form, you’re ready to start making your bisque mold on top of it. Roll out a slab of clay about ¼-inch thick and place it over your drape mold (figure 1). If your drape form is glass or metal, place a piece of plastic wrap between the form and the clay to keep the slab from sticking. Cut and smooth the bottom edge so that it’s a straight, even and level line, following the base of the form.

 

 

Figure 1

Now for the fun! Stamp into the clay surface as if you were making a piece with a concave, design (figure 2). Make your own clay stamps or use items from nature such as shells, pine cones, and leaves. Using a potter’s wheel or a banding wheel and a ribbon or loop tool, carve borders or defining lines to frame in your design. Remember that whatever is carved into the clay will be raised and reversed in your future piece. As you create your design, think about balance, harmony, movement, and emphasis.

 

 

Figure 2

If the mold is round, place it on the wheel, center it and secure it with lugs of clay as you would when trimming and use a metal rib to create a spiral in the middle giving it a “thrown” appearance if you wish. Usually, a small leaf finds its way into the interior of the design on my work (figure 3). Once you’ve finished the design work, wait until the piece is leather hard and remove it from the mold. Let the form dry slowly, then bisque fire it.

 

 

Figure 3

Final Convex Piece
Roll out a slab of clay and place it over the bisque mold (figure 4).

 

 

Figure 4

With a small hand roller firmly roll the clay from the center of the mold out toward the edge (figure 5). Use a rubber rib to smooth this surface after rolling. Cut and smooth the bottom edge with a needle tool following the base of the mold.

 

 

Figure 5

At this point, you can extrude a ½-inch thick coil to add a raised foot to the form. The clay and the coil need to be the same wetness. If the form is round, place the mold on the wheel, center it, and secure it with clay lugs, and throw the foot. Using your pin tool, make two concentric circles about a half inch apart while the wheel is spinning to indicate where you will place the coil. Place the coil (figure 6), then press downward on the inside and outside of it to adhere it to the base surface.

 

 

Figure 6

Once it’s fastened, firmly give the coil an upward pull to create height, then smooth the surface with a chamois or sponge (figure 7).

 

 

Figure 7

To add the coil to an oval, square or oblong form, simply eyeball where you want it. Lay the coil down and be sure to bevel the edges where they join to secure the connection. Use a flat wooden tool to smooth the coil on the inside creating a secure join. When the coil is secured, smooth the transition between the coil and pot with a rubber rib (figure 8).

 

 

Figure 8

Use similar clay stamps on the outside of the foot to tie the patterns together (figure 9).

 

 

Figure 9

Revealing the Finished Piece

 

Clay dries and releases very quickly on a bisque-fired mold, which allows for several pieces to be made on the same mold each day.

 

When the platter is leather hard, pop it off of the mold. At this point, clean up the outer edge with a fettling knife. The outer edge can be a straight line or follow the contours of the stamped shapes (figure 10). After cutting, smooth the edge with a sponge. I sometimes add slip-trailed elements or do more carving on the surface of the piece. Adding handles to larger pieces enhances the form and makes them easier to use. Since you’ve already added a foot, the piece is now complete.

 

 

Figure 10

Glazing

 

Semi-matte, shiny, or transparent glazes work best in highlighting the raised surface design on these pieces. I use one glaze on the whole piece, then brush another accent glaze or stain onto the leaves, shells, etc. Spraying or dipping the piece all at one time with no glaze overlapping is best, as overlaps create lines that will distract from the raised pattern.

 

Final Thoughts

 

Creating and using these molds offers me endless possibilities. As a pottery instructor, it assures quick success for the most novice of my clay students. In addition to helping beginners, this technique presents an excellent road into exploration when used by seasoned clay artists as well.

 

Nancy Zoller is a professional potter residing in Loveland, Colorado. To see more, go to: www.nancyzollerpottery.com.


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