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About Ceramic Greenware: Article or Project

Working with greenware.

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In a nutshell, greenware is raw clay. Clay that has not been fired or ‘baked’. Potters throw pots and until they are fired, they are greenware. It does not matter if an item has been sculpted by hand, cast with a mold, earthenware, porcelain, stoneware or any other form of clay, until it is fired it is raw or greenware.

While in the unfired state, it can be broken quite easily. Most fragile is cast porcelain, then cast earthenware, next pottery, then sculpted bodies. This is primarily because of the density and thickness of the item as well as the fragility of the clay body.

When handling raw clay ware, it is important that you support the bottom rather than trying to pick it up from the top as the weight causes stress and can cause the piece to snap and or crumble.

In its raw form, most clays can be crushed and recycled; however once fired, they cannot. There are two major differences between clay bodies - Low-fire and high-fire. Low-fire clays are those that require lower temperatures to reach maturity as opposed to those which require higher temperatures.

It is common practice to add varying chemicals and other minerals to a clay base to produce clay bodies suited to more specific needs and results. That is how porcelain was discovered hundreds of years ago (around 700 AD) and the further advancement of porcelain to bone china. Bone china is the most translucent of all clay bodies. Stoneware on the other hand is the most dense.

Interestingly enough, both porcelain and most stoneware clays are considered high-fire clays and require extreme temperatures to reach maturity. Earthenware on the other hand is a low-fire clay and matures at somewhat cooler temperatures.

There are several stages of clay once it becomes shaped. Initially it is quite wet (wet-ware). During the drying process it reaches a leather hard stage wherein the object is about 75% dry. Clay at this stage is very firm, yet may still be somewhat pliable, but not very. This is the stage for any trimming and more detailing. Pieces can be joined together somewhat safely at this stage. Next the clay becomes ‘bone dry’. That is achieved when the clay is 100% moisture free. From the time the item begins its drying process and until it is fired, it is considered to be greenware. Once it is bone dry, you can still affect certain improvements and detailing with some care as it is now very brittle. This is where the item is fine-tuned and any blemishes are cleaned off or repaired.

While in greenware stage, there are many ways to paint or add further designs which will become permanent once fired. Most generally glazes are not used until AFTER the clay has been fired to maturity as it shrinks anywhere from 10-20 percent during firing depending upon the type of clay.

 

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