Underfired

[W]hen the enamel is thick and a little underfired it will be lighter in color and have a pitted surface. Going further, extremely thick areas that are well underfired will be blistered, cracked, or bubbly.

In terms of its body composition, Ru ware is essentially a slightly underfired (1200°–1250°C) stoneware with a high-alumina, low-iron clay of typical north Chinese composition.

An underfired or short-fired piece is likely to break if you attempt to change its shape because it is built of many small particles of silver, joined together at the edges. A properly made, fully sintered and fully annealed metal clay piece should be able to stand up to any traditional metalsmithing technique.

Some old, underfired clay pantiles might be damaged by button mosses rooting in cracks and fissures. But most post-war tiles are hard enough to withstand a bit of moss growth.

Steak lovers want a charred surface and a rare, even cold, center. A high-tech overfired broiler is the secret. This kind of broiler delivers tremendous heat that is both predictable and consistent. Some establishments use the underfired version, which has the advantage of searing the bits of dripping fat, which gives the meat a barbequed taste. [...] The disadvantage of the underfired grill is the potential for flareups, which can cause a burned spot or carbonization. Not only do these taste bad, but they are also carcinogenic. Home grills are underfired; they must be watched carefully.

Under-fired (under-heated) grills. The heat source for these is underneath the grill. Under-fired grills are used to cook food quickly, so they need to reach a high temperature. This type of grill makes criss-cross marks on the food, known as quadrillage.