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All colours of Greek black-red vase painting are produced by the different concentrations of iron in the clay, and the different degrees to which that iron is oxidised during firing. Iron has the special feature of forming oxides of various colours, including grey Iron(II) oxide (FeO), red Iron(III) oxide (Fe 2 O 3 ), and deep black magnetite ...
Terracotta flower pots with terracotta tiles in the background Due to its porosity, fired earthenware, with a water absorption of 5-8%, must be glazed to be watertight. [ 11 ] Earthenware has lower mechanical strength than bone china, porcelain or stoneware, and consequently articles are commonly made in thicker cross-section, although they are ...
Alumina, often derived from clay, stiffens the molten glaze to prevent it from running off the piece. [7] Colorants, such as iron oxide, copper carbonate or cobalt carbonate, [7] and sometimes opacifiers including tin oxide and zirconium oxide, are used to modify the visual appearance of the fired glaze.
Sodium from the salt reacts with silica in the clay body to form a glassy coating of sodium silicate. The glaze may be colourless or may be coloured various shades of brown (from iron oxide), blue (from cobalt oxide), or purple (from manganese oxide). [1] [2] [3] Except for its use by a few studio potters, the process is obsolete. Before its ...
Maiolica charger from Faenza, after which faience is named, c. 1555; diameter 43 cm, tin-glazed earthenware Tin-glazed (majolica/maiolica) plate from Faenza, Italy. Tin-glazed pottery is earthenware covered in lead glaze with added tin oxide [1] which is white, shiny and opaque (see tin-glazing for the chemistry); usually this provides a background for brightly painted decoration.
Traditional pueblo pottery is handmade from locally dug clay that is cleaned by hand of foreign matter. The clay is then worked using coiling techniques to form it into vessels that are primarily used for utilitarian purposes such as pots, storage containers for food and water, bowls and platters.
A series of analytical studies have shown that the striking black gloss with a metallic sheen, so characteristic of Greek pottery, emerged from the colloidal fraction of an illitic clay with very low calcium oxide content. This clay slip was rich in iron oxides and hydroxides, differentiating from that used for the body of the vase in terms of ...
The iron in the clay absorbs oxygen and becomes the red or red-brown iron(III) oxide. The resulting pottery has a red-brown colour. [25] The simplest and earliest firing method is the open fire. The vessel to be fired is covered and filled with flammable material. It is placed on a flat piece of ground, surrounded by a low wall, or put in a pit.