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Welcome to your workshop! Whether you’re a wheel thrower, a handbuilder, a glaze-testing geek, or all of the above, we’ve pulled together several ceramic projects and references you can use in your own studio. The articles in Workshop Handbook: Clay Projects and Studio Resources are a selection of project ideas that are meant to be a ceramic workshop in print—except you can take this one into your own studio and refer back to the clay projects as needed. So pick a project and get to the clay studio!
Here’s an excerpt from one of the mini pottery workshops you’ll find in the 2013 Workshop Handbook: Clay Projects and Studio Resources:
by John Britt
Defining the Terms
Copper Oxide—Black Copper Oxide (Cupric) CuO; melts at 2419°F (1326°C). Red Copper Oxide (Cuprous) Cu2O; melts at 2255°F (1235°C). Cupric oxide decomposes at 1847°F (1008°C) to cuprous oxide and oxygen. It is an active flux, so adding it to a glaze may cause the glaze to run. It has a high coefficient of expansion/contraction, which may increase crazing in larger amounts. It is toxic, volatile (fume hazard), and can leach into food. It can migrate through a clay body, and almost any copper glaze with a matte black surface will leach copper in the presence of acidic liquids. It can also cause pinholing.
Copper Carbonate—The idealized formula for this green powder is CuCO3, but the material may come as a variety of compounds and may contain impurities. Cu2(OH)2CO3 (Malachite) may be a more accurate formula representation. Since it is reactive chemically, it disperses better in a glaze thus giving more even results than copper oxide. It off gasses and can cause pinholes or blisters in a glaze. At approximately 572°–608°F (300°–320°C) copper carbonate releases carbon dioxide and water, and then at 1922°F (1050°C) it loses more oxygen as it restructures. Copper carbonate makes greens in amounts of 5% or less, blacks above 5%, and at 0.3–0.8% it makes blues in oxidation and copper reds in reduction. Approximate conversion: 5% copper carbonate = 3.6% black copper oxide = 3.24% red copper oxide.
Copper Sulfate—This blue crystal is an agricultural fungicide. It is soluble in water, starts decomposing at 302°F (150°C), loses four water molecules by 392°F (200°C), then changes to copper oxide and sulfur trioxide by 1202°F (650°C). Often used in pit and low-temperature saggar firings. Produces grays in soluble salt firings as well as pinks and reds in heavy reduction.
Copper Chloride—Often used in water soluble metal salt firing (aka water coloring on porcelain). Produces burgundy colors in pit and saggar firings. Copper Filings—Chips of copper metal. Copper filings are sometimes sprinkled in or on a wet glaze to give black spots with flashes of red on the perimeter.
Copper Glaze Tips
Oribe pieces are decorated on one side with an iron oxide design over a transparent glaze while the other side is decorated with a transparent copper green glaze. Then they are fired in oxidation. Oribes can get a scummed layer on top that dulls the color. The traditional method for getting a clearer copper Oribe is to soak chestnut husks in water and then soak the pots in this acidic solution. But today potters just use a weak muriatic acid (hydrochloric acid) solution. (This is toxic so use in a well-ventilated area with safety glasses and a mask.)
Copper volatilizes above 1877°F (1025°C) and becomes increasingly volatile, making it a fume hazard. The volatilization can affect adjacent pots, particularly those with tin whites or celadons, resulting in a pink blush. This property can also be used to decorate a pot. Glazing the inside of a saggar with an Oribe glaze and then placing a tin white glazed tea bowl in the saggar will give a delicately blushed pink tea bowl. Copper glazes are often used in soda and salt firings because the introduction of volatile sodium during the firing turns copper glazes various shades of blue/turquoise/green. Sometimes potters use high amounts of copper (10%) in a green salt glaze, which turns black, but when the salt fumes hit that part of the pot, the area turns deep green on one side with the other side of the pot fading to black.
Raku: With sufficient post-firing reduction, the copper oxide/carbonate can be reduced to metallic copper finishes. These copper lusters are only microns thick so they can reoxidize to produce green colors (much like a penny oxidizes) if the pots aren’t coated with a polyurethane sealant. Copper is also used in Islamic luster firing techniques as well as Egyptian Paste (ancient Faience), which is a self-glazing, low-fire clay body that goes back 7000 years. It was probably discovered by firing sand, clay, and salt or soda ash. Then colorants were added to make colorful beads and ornaments.
To see the rest of this article, download your free copy of the Workshop Handbook: Clay Projects and Studio Resources…
Here’s what else is included in the Clay Workshop Handbook:
Taking influences from Guatemalan textiles, Lauren Karle creates surface designs and layers pigments prior to forming her pots resulting in pieces that appear to be made of fabric.
Create functional vessels with clean lines using techniques from studio potter and designer Billy Lloyd.
Roulettes are a great way to create textures on your surfaces, and artist Russel Fouts shares a great tip for making these difficult-to-design tools.
Blending two colored clays as a gradient challenged a former NASA software engineer named Judith Skinner who solved the problem. Chris Campbell reveals the skinny on the technique.
About Ceramic Arts Daily:
Ceramic Arts Daily is a free online website and newsletter written and produced for the benefit of potters and ceramic artists worldwide. The newsletter features both renowned and emerging artists, their work, techniques and artistic perspectives. Regular features include tips and techniques designed to help every artist expand their skill set and widen their artistic horizons. Ceramic Arts Daily also delivers video tips, in which potters and ceramic artists demonstrate various projects and processes. Think of them as e-workshops!
Ceramic Arts Daily is designed to be interactive, inviting your comments and fostering a community in which each person can contribute to the growth of their own and others’ skills. You may be surprised at what you learn!
Ceramic artists on Ceramic Arts Daily know what ceramic art is all about – from functional pottery to abstract ceramic sculpture. This is about community. You’ll be drawn in by artists’ stories, inspired by their work and find confidence to try some of their techniques. With Ceramic Arts Daily, you’ll learn a little bit of everything. Then you can choose the techniques you enjoy the most to create something new!
So start today by downloading our free 2011 Clay Workshop Handbook: Knowledge and Techniques for the Pottery Studio. Then, get ready for Ceramic Arts Daily to introduce you to new artists and show you new techniques!
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