CERAMICS CLAY SLAB Container
CLAY • Mud; moist, sticky dirt. • In ceramics, clay is fine-grained,firm earthy material that is plastic when wet, brittle when dry, and very hard when heated.
The most common types of ceramic clays are: • earthenware, • stoneware, and • porcelain.
Earthenware • Earthenware is a low-fire clay that is porous and not waterproof. • It can be made waterproof by glazing it. • You will use earthenware clay to roll out a slab and create a ceramic container.
Clay Slab Plan • First plan on newsprint. • What will be your theme…Nature or man-made? • What shape expresses your theme? • What decoration helps express the theme? • Does the container need additions…“feet”, handles, top, lid, pictures?
Clay Slab Plan • Roll out a slab of clay • Cut the sides, then bottom & top
Clay Slab • REMEMBER when measuring, clay has thickness. Decide how the sides will overlap and how thick the slabs will be before figuring the size of the bottom of the slab piece. For example: or
When the slabs are rolled out, and they are cut to size, they should be allowed to dry to the leather-hard stage before assembling .
Leather-hard This is the first stage of drying. There is still moisture in the clay, but it is just dry enough to hold its shape and not “slump” This stage of drying is called leather-hard.
When the slabs are leather hard, they can be assembled by scoring (scratching) and slipping the edges to be joined. • What is scoring and slipping????
Score the clay that is to be joined Make scratches in the pieces of clay to be joined together. Roughen the surface.
Add clay slip to the scored piecesto join them together. • Clay slip is a fine, liquid form of clay used to cement together parts that have been formed separately. Mixing finely ground clay with water makes clay slip.
The scratched and slipped edges should be pressed firmly together and the joints blended with a finger tip or a small tool. Square corners should be given additional support on the inside. Make a coil the size of an earthworm, lay it carefully in the inside corner and smooth it into each side of the corner.
Bone Dry • When finished, your greenware container needs to be thoroughly dry before it can be fired. • This stage of drying is called bone dry.
Greenware - Bisque • Unfired clay is called Green ware • Fired clay is called Bisque ware
Firing • Clay is hardened by heating it to a high temperature, thus fusing the clay particles. Temperature in kilns can reach 2500 degrees.
Glaze • The bisque clay container is now ready to be glazed. • Glaze is a coating of material applied to ceramics that forms a glass-like surface when fired a second time.