Frit
Frits form an important part of the batches used in compounding enamels and ceramic glazes; the purpose of this pre-fusion is to render any soluble and/or toxic components insoluble by causing them to combine with silica and other added oxides.
According to the OED, the origin of the word "frit" dates back to 1662 and is "a calcinated mixture of sand and fluxes ready to be melted in a crucible to make glass".
[8] Ultimately the frit consists of cuprorivaite (CaCuSi4O10) crystals and "partially reacted quartz particles bonded together" by interstitial glass.
[9] Despite an argument to the contrary, scientists have found that, regardless of alkali content, the cuprorivaite crystals develop by "nucleation or growth within a liquid or glass phase".
[14][15] At Amarna, archaeologists have found blue frit in the form of circular cakes, powder residues, and vessel fragments.
[16] Analysis of the microstructures and crystal sizes of these frits has allowed Hatton, Shortland, and Tite to deduce the connection among the three materials.
[17] In On Architecture, the first century BC writer Vitruvius reports the production of 'caeruleum' (a blue pigment) at Pozzuoli, made by a method used in Alexandria, Egypt.
[9] The ultimate product is composed of copper-wollastonite ([Ca,Cu]3Si3O9) crystals and a "glassy phase rich in copper, sodium, and potassium chlorides".
[17] An Akkadian text from Assurbanipal's library at Nineveh suggests that a frit-like substance was an intermediate material in the production of raw glass.
[27] An excerpt of Oppenheim's translation of Tablet A, Section 1 of the Nineveh text reads: You keep a good and smokeless fire burning until the 'metal' [molten glass] becomes fritted.
[31] Moorey has defined this intermediate step as "fritting", "a process in which the soluble salts are made insoluble by breaking down the carbonates, etc.
[38] In their reconstruction of the manufacture of vitreous faience, Tite et al. propose that the initial firing of raw materials at 1100–1200 °C produces a cobalt-blue frit, which is then ground, molded, and glazed.
[42] Nevertheless, determining the exact technical relationships among the frit, glass and faience industries is an area of current and, likely, future scholarly interest.
The excavations at Amarna offer a spatial confirmation of these potential relationships, as the frit, glass and faience industries there were located "in close proximity" to one another.
A recipe for "fritware" dating to c. 1300 AD written by Abu’l Qasim reports that the ratio of quartz to "frit-glass" to white clay is 10:1:1.
[51] Microscopic analysis reveals that the material that has been labeled "frit" is "interstitial glass" which serves to connect the quartz particles.
Famous manufacturers of the 18th century included Sèvres in France, and at Chelsea, Derby, Bow, Worcester and Longton Hall in England.
This factory, established in 1857, produces ware that is characterised by its thinness, slightly iridescent surface and that the body is formulated with a significant proportion of frit.
[1] A small manufacturing cluster of fritware exists around Jaipur, Rajasthan in India, where it is known as 'Blue Pottery' due its most popular glaze.
[58] Frits are typically intermediates in the production of raw glass, as opposed to pigments and shaped objects,[59] but they can be used as laboratory equipment in a number of high-tech contexts.
[63] In 2008, the Spanish ceramic frit, glaze and colours industry included 27 companies employing nearly 4,000 people with a combined annual turnover of approximately €1 billion.
