THINGS YOU NEED TO KNOW ABOUT CERAMIC WARE
Due to the techniques and substances often used in creating ceramic ware, every precaution has been taken to ensure the safety of the end user. The information listed below offers an overview of ceramic ware and helpful information everyone should know.
What is Vitrified Ceramic Ware?
Ceramic ware that is vitrified has been fired under extremely hot temperatures and tends to be heavy, non-porous and non-translucent in nature. Any ceramic ware that is capable of absorbing less than 0.2 percent of its own weight when placed in boiling water for five hours and then submerged in water for an additional 19 hours is classified as vitrified.
What Separates Porcelain, Stoneware and Bone China?
Porcelain is a derivative of a white clay known as Kaolin. It is fired at temperatures that exceed 1300 degrees C. The fired Kaolin clay holds its stark coloring, giving Porcelain its crisp white appearance. Because the Kaolin clay is more pliable, this material lends itself to creating more complex and unique shapes. Porcelain undergoes two firings and provides a harder, yet less durable finish than China ware. Porcelain is considered more vitrified than stoneware.
Stoneware on the other hand is fired much differently. Unlike Porcelain, which becomes vitrified after two firings, Stoneware achieves this state after only one firing and yet, the temperatures used are generally lower than those used in firing Porcelain. The single firing at the reduced temperature is what produces a richer color and makes stoneware decorating easier than porcelain decorating.
Bone China begins with translucent white clay comprised of bone ash. Generally speaking, all Bone China must contain a minimum of 25% bone ash.; The exception is in England, which requires the bone ash ratio be at least 50%. Bone China is known for its elegant, refined qualities.
Decorating With Glaze
There are three approaches to decorating Porcelain, Stoneware and Bone China.
Under-Glaze Decorating
Under-glaze decorating is a translucent glaze which is most commonly used on a China rather than Stoneware or Porcelain. This clear glaze is added to the bisque ware and/or green ware directly. The objective of under-glazing is to protect the fine China from every day use and potential erosion.
On-Glaze Decorating
This method of decorating is selected when adding bright colors and metallics such as gold and platinum. On-glaze decorating is added directly onto the ceramics, which have already been fired and glazed. Because brighter colors and metallic decorating cannot withstand higher temperatures, on-glazing requires a lower temperature for firing. This method of decorating can cause ceramics to deteriorate with everyday use and exposure to detergents. Any potentially toxic materials used in this decorating glaze technique may be vulnerable to leaching.
In-Glaze Decorating
In-glaze is a technique in which the decorative glaze is literally fused into the glaze, making it extremely durable and resistant to every day use and erosion. With in-glazing, the decorative colors are added to ceramics that have already been glazed and completely fired and are then fired again under extremely hot temperatures. The extreme heat causes the color to melt into the glazed surface. Not all colors can withstand the exceedingly hot temperatures required to achieve this technique.
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