What is "hessian crucible"

Hessian \Hes"sian\, a. Of or relating to Hesse, in Germany, or to the Hessians.

Hessian boots, or Hessians, boot of a kind worn in England, in the early part of the nineteenth century, tasseled in front.
--Thackeray.

Hessian cloth, or Hessians, a coarse hempen cloth for sacking.

Hessian crucible. See under Crucible.

Hessian fly (Zo["o]l.), a small dipterous fly or midge ( Cecidomyia destructor). Its larv[ae] live between the base of the lower leaves and the stalk of wheat, and are very destructive to young wheat; -- so called from the erroneous idea that it was brought into America by the Hessian troops, during the Revolution.

Crucible \Cru"ci*ble\ (kr[udd]"s[i^]*b'l), n. [LL. crucibulum a hanging lamp, an earthen pot for melting metals (cf. OF. croisel, creuseul, sort of lamp, crucible, F. creuset crucible), prob. of German origin; cf. OHG. kr[=u]sul, LG. kr["u]sel, hanging lamp, kroos, kruus, mug, jug, jar, D. kroes cup, crucible, Dan. kruus, Sw. krus, E. cruse. It was confused with derivatives of L. crux cross (cf. Crosslet), and crucibles were said to have been marked with a cross, to prevent the devil from marring the chemical operation. See Cruse, and cf. Cresset.]

1. A vessel or melting pot, composed of some very refractory substance, as clay, graphite, platinum, and used for melting and calcining substances which require a strong degree of heat, as metals, ores, etc.

2. A hollow place at the bottom of a furnace, to receive the melted metal.

3. A test of the most decisive kind; a severe trial; as, the crucible of affliction.

   Hessian crucible (Chem.), a cheap, brittle, and fragile, but very refractory crucible, composed of the finest fire clay and sand, and commonly used for a single heating; -- named from the place of manufacture.

A Hessian crucible is a type of ceramic crucible that was manufactured in the Hesse region of Germany from the late Middle Ages through the Renaissance period. They were renowned for their ability to withstand very high temperatures, rapid changes in temperature, and strong reagents. These crucibles were widely used for alchemy and early metallurgy. Millions of the vessels were exported throughout Europe, Scandinavia, and the colonies in the Americas. The crucibles were made by firing kaolinitic clay at temperatures greater than 1100℃, forming mullite. Mullite is an aluminum silicate only described in the 20th century and is responsible for the excellent properties of the Hessian crucible.