If oxide of copper is added to a glass mixture containing a strong reducing agent, a glass is produced which when first taken from the crucible is colourless but on being reheated develops a deep crimson - ruby colour.
During the process of manipulation, whether on the chair or whilst the glass is being reheated, the rod must be constantly and gently trundled to prevent the collapse of the bulb or vessel.
The plaques thus formed could be reheated and fashioned into the bases of bowls and drinking vessels.
The former was made, as described by Theophilus, from cylinders, which were split, reheated and flattened into square sheets.
Osmond.) Silver-copper [copper= 15% silver - 85%] reheated to purple colour.
That to which the hardened steel is thus reheated, the more is the molecular rigidity relaxed, the farther on does the transformation go, and the softer does the steel become; so that, if the reheating reaches a dullred heat, the transformation from austenite into ferrite and cementite completes itself slowly, and when now cooled the steel is as soft and ductile as if it had never been hardened.
This bloom is immediately rolled down into a long flat bar, called " muck bar," and this in turn is cut into short lengths which, piled one on another, are reheated and again rolled down, sometimes with repeated cutting, FIG.