Stoneware

Stoneware is a form of kitchen and utility ceramics made of fired clay. The process results in items that are strong and durable. The levels of heat and cold it can sustain means stoneware is very versatile. Stoneware is also nonporous, so it can hold water and other liquids. The earliest known stoneware dates to about two thousand years ago. It is different from earthenware—an older, similar form of pottery also made from fired clay—and porcelain, a much more delicate type of fired clay pottery.

Background

All stoneware is considered to be ceramic, but not all ceramics are stoneware. The word ceramic comes from the Greek keramos, which means "pottery." To make ceramic items, the raw materials for the clay are gathered and prepared. This may involve mixing in additives, depending on the final purpose of the item. The clay is shaped by hand on a potter's wheel or with the use of a mold. The artist then fires, or bakes, the clay to a certain temperature, which depends on the clay type. This firing is done in special ovens called kilns that are designed to reach and maintain temperatures above 2,000 degrees Fahrenheit (1,093 degrees Celsius). In many cases, including some stoneware, the artist will then coat the fired pottery with a mixture of clay. The artist may color and fire it again to turn the coating into a protective glaze. The three main types of ceramic pottery used for kitchen and utility purposes include stoneware, earthenware, and porcelain. However, porcelain pieces are generally more delicate in shape and design while earthenware and stoneware are more sturdy and durable.

The three types of ceramics are differentiated by several characteristics, starting with the clay from which they are made. These clays are defined by their absorption rate, or how quickly each clay takes on water. The absorption rate is based on a specific formula involving the clay's weight after two hours of soaking in water and its dry weight, or the weight before it is soaked. The absorption rate for stoneware clay is 2 to 5 percent, as opposed to the 10 to 15 percent rate of earthenware and the 0 to 1 percent rate of porcelain.

While earthenware is fired at around 1,915 degrees Fahrenheit (about 1,046 degrees Celsius), stoneware requires a temperature of about 2,185 degrees Fahrenheit (about 1,196 degrees Celsius). However, stoneware can be fired in a range between 2,012 and 2,372 degrees Fahrenheit (1,100 to 1,300 degrees Celsius).

The type of clay used and the firing temperature are two of the things that distinguish stoneware from earthenware. Another characteristic of stoneware is that it is vitreous, or glass-like. The clay that is used for all ceramics starts as dirt or mud, often found along rivers, creeks, and other freshwater bodies. The dirt is gathered and cleaned to remove sticks, rocks, and other impurities. Then it is combined with water and specific types of minerals to create the type of clay desired. Stoneware clay is generally grayish in color, though some are found in shades of beige and brown. Based on the condition of the raw clay, various minerals can be added to make it more vitreous.

The oldest form of ceramics is earthenware. Remnants of earthenware pottery dating back fifty thousand years has been found. Stoneware is much more recent. It is believed to have originated in China about two thousand years ago, when artisans discovered how to build kilns that could reach the higher temperatures needed to fire stoneware. Stoneware then spread across Asia and into the Middle East and Europe as traders and warriors moved throughout these areas. The earliest stoneware made in the United States dates to around 1750. By the nineteenth century, many stoneware companies were in operation, and these businesses developed their own distinctive designs for the items they produced. For example, some companies used a specific cobalt blue glaze, which worked well in various types of kilns. In many cases, salt was thrown into the kilns during firing to help the glaze take on a special shine. During the eighteenth and nineteenth centuries, stoneware was used to hold grain, seasonings, and cooking fats, since it is impervious to liquids and did not absorb smells from the items held inside. Stoneware crocks and vessels enabled people to store wet food, such as pickles in brine, or foods that needed to be kept dry, such as grains, to preserve them for off-season use. Nevertheless, many stoneware producers closed once refrigeration came into use and provided a better way to store food.

Overview

Stoneware in the twenty-first century is usually designed as everyday dishware because it is durable and can handle constant use. Properly made stoneware is resistant to heat and cold, can hold liquids, is dishwasher and microwave safe, can be used to store food in the refrigerator or freezer, and can be used in the oven. Some stoneware is unglazed, while other items have a glaze that provides color and a shiny, matte, or satin finish. This versatility makes it very useful for kitchen dishes used for baking, storing, and serving food. A number of well-known brand name dishware manufacturers—including Fiesta, Dansk, and Pfaltzgraff—feature stoneware.

In addition to standard kitchen items like plates, mugs, and baking dishes, the sturdiness of stoneware makes it useful for storage items, such as large crocks for pickling. Stoneware is also useful for things that need to withstand high heat, such as oven stones used for baking bread and pizza. Stoneware is often used to make decorative items for gardens, since it can withstand temperature changes and the effects of precipitation.

It is possible to tell whether a ceramic item is stoneware by examining it carefully. Unlike porcelain, stoneware is opaque and light does not shine through it. The clay that makes stoneware usually turns a creamy yellow-brown color. If any unglazed areas show this color, the item is likely stoneware. Exposed areas of earthenware, such as a chipped area on a plate or cup, will be white. Stoneware will be darker and have a textured appearance.

Bibliography

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