Overfired

At this point overfiring begins, as is shown particularly by the volume curve, which indicates decided bloating, so that at 1450°C the clay has about the same volume it had at 1050°C before vitrification took place. At 1450°C it is, therefore, decidedly overfired. However, its excellent burning behavior is apparent from the long temperature range.

A large percentage of all Late Horizon fragments at this site was overfired, to the point where many were vitrified, black to dark brown, and misshapen, some with blistered surfaces. This observation leads me to conclude that these fragments probably formed the discards from a pottery workshop, since overfired fragments of this kind are very rare in other refuse sites.

Overfired Glaze This occurs when a glaze has been fired above the temperature for which it has been compounded. It may also occur if the glaze has been soaked for too long at or near the top temperature. Although the first cause is the most common, the second should not be overlooked. An overfired glaze may run off the object onto the kiln shelf or form a pool of glaze inside a pot. In some cases overfired glazes look thin because some of the glaze constituents have volatilized, or because the glaze has become so fluid that it has soaked into the body.

First, there are more than 300 ceramic wasters distributed throughout the deposit, as well as small numbers of burned and overfired sherds and badly deformed vessels. Some vases could not be fitted together properly, presumably because they had been broken during firing, and their parts subsequently had been warped [...].

An overfired biscuit has insufficient porosity for glazing. An overfired body warps and bloats. An overfired glaze often blisters by the volatilization of part of its composition. It also reaches a stage where its viscosity is too low to keep it on the pot.

Overfired grills, or salamanders, can, in addition, be used for making toast and salamandering. They have the heat source above the food [...]. This may comprise sets of burners firing below refractory or metal frets, or surface combustion plaques.

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