March 11, 2009
Casting Call: How to Mix Casting Slip for Sculpture and Pottery; Plus 3 Great Slip Casting Tips
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Slip casting opens up endless possibilities for creativity with clay. But it can also be an intimidating process for the beginner. So we are trying to create a reliable collection of information on this technique on Ceramic Arts Daily. Today, ceramic artist Valerie Zimany explains how to make a casting slip out of the clay body she uses and gives some handy tips to remember when working with molds and clay. Not only are these tips helpful to the novice, but practicing slip casters should also find them helpful. We’ll also link you to some of the other resources already on Ceramic Arts Daily. - Jennifer Harnetty, editor. |
| 3 Great Slip Casting Tips
Keep your molds clean! |
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Why is my mold growing a beard? A mold that is grows a fuzzy white beard is a mold that is getting old and is most likely very worn out! This phenomenon is particularly common with sodium silicate. With repeated castings, the sodium silicate in the casting slip will work its way through the capillaries of the plaster and form crystals on the surface. Wiping the mold down with a vinegar/water solution can help clean it, but your mold may be reaching the end of its usefulness. Generally, Darvan is a little easier on molds than sodium silicate, and can help your molds last longer (though it must be used in a higher ratio and is more pricey than sodium silicate). |
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Gang Molds - Efficiency in Numbers Long a staple of industry, gang molds are a great way to cast multiple pieces within one mold. This method allows you to spend less time making molds, will speed up your production of multiples and will give you consistent results from one cast to the next. Gang molds can easily be both one or two-piece molds and can share the same sprue hole. The mold is made in the same way a single object mold is created but several objects will be placed on the initial clay bed at once. Be sure to allow for an ample amount of space between each object, approximately an inch of plaster so there will be sufficient absorption of water from the casting slip. The rest of the mold will be made and cast similar to single object molds. |
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Download your free copy of the Buyers Guide to Ceramic Supplies and Materials to learn where slip-casting materials can be purchased.
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*For cone 10, use Custer feldspar instead of nepheline syenite. Mixing a Batch of Casting Slip from UArts Clay Body:
The water should be no more than 50% of the total weight of the dry materials. Darvan should be 0.4% of total weight. Bentonite should be 0.5% of total weight-up to 1% if desired. A batch of 10,000 grams of dry materials, when mixed with water, makes about 5 gallons of slip. Step 1 Blunge water and Darvan with a heavy-duty drill and a squirrel-cage or jiffy mixer. Add the bentonite and continue blunging until thoroughly mixed.
Add dry materials while continuing to mix: After mixing thoroughly, add up to 18g (0.2%) more Darvan (no more than 0.6% total) as needed. Small amounts of water may also be added to improve viscosity (use drops of water at a time and go slowly). Step 3 Step 4
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renee | September 30th, 2009 at 11:14 am
how can you keep bubbles off you pottery when you are glazeing?
renee | September 30th, 2009 at 11:15 am
how are some ways you can get cool effects on your work.