whiteware, any of a broad class of ceramic products that are white to off-white in appearance

and frequently contain a significant vitreous, or glassy, component. Including products as diverse

as fine china dinnerware, lavatory sinks and toilets, dental implants, and spark-plug insulators,

whitewares all depend for their utility upon a relatively small set of properties: imperviousness to

fluids, low conductivity of electricity, chemical inertness, and an ability to be formed into

complex shapes. These properties are determined by the mixture of raw materials chosen for the

products, as well as by the forming and firing processes employed in their manufacture.

In this article the raw materials, properties, and applications of whiteware ceramics are reviewed.

At certain points in the article there are references to specific industrial processes employed in

the manufacture of whiteware products. For more detailed description of these processes, see

industrial ceramics.

Raw materials: clay, flint, and feldspar

Whitewares are often referred to as triaxial bodies, owing to the three mineral typesclay, silica, and feldsparconsistently found in their makeup. Clay is the plastic component, giving shaping abilities to the unfired product and also serving as a glass former during firing. Flint (the

common name used in the industry for all forms of silica) serves as a filler, lending strength to

the shaped body before and during firing. Feldspar serves as a fluxing agent, lowering the

melting temperatures of the mixture.

Clay is the most important of the ingredients, and the most important clay used in fine whiteware

products is kaolin, also known as china clay. Kaolin is the only type of clay from which a white,

translucent, vitreous ceramic can be made. It is a refractory clay, meaning that it can be fired at

high temperatures without deforming, and it is white-burning, meaning that it imparts whiteness

to the finished ware. Kaolin is formed principally of the mineral kaolinite, a hydrous

aluminosilicate with a fine, platy structure; its ideal chemical formula is Al2(Si2O5)(OH)4. China

clays are composed mostly of well-ordered kaolinite, with no impurities. Lower-grade

whitewares are usually made of ball clays, which incorporate ordered and disordered kaolinite

plus other clay minerals and impurities. These impuritiesparticularly iron oxidesrender the fired ware off-white to gray or tan in colour.

Products

Whiteware products are often differentiated into three main classesporous, semivitreous, and vitreousaccording to their degree of vitrification (and resulting porosity). Proceeding from porous to vitreous, more particular product categories include earthenware, stoneware, china, and

technical porcelains. Earthenware is nonvitreous and of medium porosity. It is often glazed to

provide fluid impermeability and an attractive finish. Specific products include tableware and

decorative tile ware. Stoneware is a semivitreous or vitreous whiteware with a fine

microstructure (that is, a fine arrangement of solid phases and glass on the micrometre level).

Products include tableware, cookware, chemical ware, and sanitary ware (e.g., drainpipe).

All vitreous whitewares are often referred to as porcelains, but in the ceramics industry a

distinction is maintained between the true porcelains (or technical porcelains) and china. China is

vitreous whiteware for nontechnical applications. Because of its high glass content, it can be

used unglazed, though it also can be glazed for aesthetic appeal. China is known for high

strength and impact resistance and also for low water absorptionall deriving from the high glass content. Typical products include hotel china, a lower grade of china tableware with a

strength and impact resistance suiting it to commercial use; fine china (including bone china), a

highly vitreous, translucent tableware; and sanitary plumbing fixtures.

Technical porcelains, like china, are vitreous and nonporous. They are similarly strong and

impact-resistant, but they are also chemically inert in corrosive environments and are excellent

insulators against electricity. Applications include chemical ware, dental implants, and electric

insulators, including spark-plug insulators in automobile engines.