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FREQUENTLY ASKED QUESTIONS


The following questions are frequently asked our Staff. if you have any additional questions not posed here, please don't hesitate to contact us.
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CLAY MODELING MATERIALS

What is self-hardening clay?

Self-hardening clays (also known as air-dried, air-hardening or non-firing) should not be fired in a kiln, and are generally ceramic clay body formulas with a natural additive, such as cornstarch, to make them harden. They are not meant to replace kiln-fired ceramic clay, cannot be used to produce functional ware (that is, to hold foodstuffs), and cannot be left outside exposed to the elements. Pieces made using these clays are items for display only. It is porous and cannot hold liquid unless sealed on the inside surface.

What is the difference between Claystone and Boneware?

Claystone, works like plastilina and is usually used over an armature, an internal support device. The clay material generally contains some type of pulp or cotton fiber filler to reduce shrinkage and thus prevent cracking. (The armature will not give when the clay shrinks due to evaporation of moisture.) Please note, there may be some degree of shrinkage when using a water-base material, so expect minor cracking if the piece is thin and modeled over a solid support.

The second type of air-hardening clay, Boneware, is used for solid direct modeling that will be supported by its own bulk. It will contain a natural hardener, but not fiber, to reduce shrinkage and will probably feel and react more like a ceramic clay to the touch and in workability.

There is another type of self-hardening material that can be air-dried or oven baked to give the piece more durability. An example of this material is Della Robbia. This type of material will not replace a kiln-fired ceramic clay that is fired in excess of 2000°F fusing the molecular structure and becoming vitrified and non-porous. Please note, for any self-hardening clay there is no known method to emulate vitrification.

How can I dry a piece of self-hardening clay?

The material should be dried extremely slowly for best effect. This is done by placing a damp cloth over the piece and drying it at room temperature slowly and evenly. It is not recommended to place the material in the sun, in an oven, or by a radiator to hasten drying. Remember to allow the piece to dry thoroughly before sealing or applying patina (coloring).

How long does it take to dry a piece made with self-hardening clay?

It depends on the thickness of your piece and the moisture content in the air. For example, if you are drying your piece near a river or other body of water, you could add an additional one to two weeks of drying time on a three-inch thick piece. The material dries from the outside in, sealing itself as it dries. For tile and thick pieces, you can try placing them on an open air rack where the air can circulate easily around the piece, to help speed the drying time. However, you want to dry the piece naturally so the clay does not crack due to a too fast drying time. HINT: You can weigh the piece prior to drying and when it is 25% lighter in weight it should be thoroughly dry since the water content of the material is usually 22-27%.

Will hardened clays be vitrified (non-porous)?

No. Air-dried materials are characteristically porous and will not hold liquids or withstand the effects of outside weather over a sustained period of time.

Can self-hardening clays be thrown on a potter’s wheel?

Boneware has been specially re-formulated to be thrown on wheels for small- to medium-sized pieces. However, since Boneware is an air-dried material, it cannot be fired. Most other air-dried materials on the market today will not stand up to the added water required to bring up the side walls on pottery, although there are products that come close.

Can the finished piece be colored?

Yes, in a variety of textures, such as clear finish or matte finish, that are directly applied to the piece. For more realistic colors, sealing the surface to be covered with clear or base paint color will allow the final coating color to adhere easily. This may be latex paint, acrylic, oil, or even water colors. You can achieve mute color effects using wood stain, wax pigmentation applications, or clothes dyes. You can also spray the finished piece with special effect paints obtained from hardware stores. We recommend a test tile be made and that you experiment to achieve best results. Number each test tile and write down what steps you have taken to create a given effect on each tile.

What are the primary carving waxes?

A type of direct modeling material, most carving waxes are derivatives of oil or petrolatum base materials. They will vary in consistency and color. In sculpture there are two popular primary waxes: Microcrystalline Wax and Roman Casting Wax. Microcrystalline Wax, also known generically as Victory Brown and micro wax, is by far the most popular wax. It is medium soft and nut-brown in color. Although it is somewhat sticky, it can be used for direct modeling. Roman Casting Wax, harder, more brittle and varying from purple to black in color, is used to make final detailed definitions prior to casting a sculpted piece as well as for carving and modeling small objects.

There are also specific formula waxes such as French Wax, a mixture of white micro, pure beeswax, and a small amount of number A4 wax (a private studio blend of Sculpture House, Inc.). This material is of medium consistency and is extremely smooth and easy to model. Finally, Pure Beeswax, extracted from bee hives, and Synthetic Beeswax are sometimes used as a direct modeling material, but because of its high cost, not often. Beeswax, a pure yellow natural wax used to dress wood or seal stone sculpture; also used in batik.
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