Ceramics artifacts have a long human history, dating back 27,000 years. Ceramics are a useful artifacts for archaeologist as they are hand made, durable, and can last thousands of years without changing from their original state.
Clay, in its natural form, is white in colour. impurities such as iron make it a different colour. When clay is heated, water evaporates and the minerals fuse to become a ceramic. This process is irreversible once the ceramic has been created, and is similar to making glass.
Identifying qualities of Historic Ontario Ceramics:
Types: There are four major groups of ceramic; coarse earthenware, fine earthenware, stoneware and porcelain. These types have different densities and are heated to different temperatures when made.
Glazes colour, decorate, waterproof, and strengthen ceramics. Glazes are comprised of a layer of glass fused to the clay through firing. They are particularly important as waterproofing earthenware as it is a very porous material.
Glazes react differently when heated depending on what they are made of. Salt
glazes, which combine silica, sodium and/or potassium with calcium (as a stabilizer), are commonly used on stoneware.
The glaze forms a thin, orange-peel like texture. Lead glazes, which contain lead and other metals tend to melt at lower temperatures making them easier to use and produce brilliant effects. Adding tin to a lead glaze creates an opaque white glaze, known as majolica, delft, or faience. Luster can be added to the glaze, by using silver or copper.
In order to determine its date, archaeologists can use both the style of a ceramic vessel, as well as the technique used to make it. One of the best ways to determine a vessel’s age is
to use its ‘Maker’s Mark’, or the mark found typically on the bottom of the object. Maker’s Marks are applied using different methods depending on the manufacturer.
Archaeologists are able to date ceramic artifacts using the maker’s mark by determining when a particular style was used. For instance, we know that printing ‘England’ was used after 1891. It became compulsory for English ceramics to be marked as a result of the McKinley Tariff Act in the United States. The bill, designed to encourage American industries, required articles imported into the USA to be clearly marked with the name of the country where it was manufactured.