FACTOID #53: If you thought Antarctica was inhospitable, think again - its land area is only ninety-eight percent ice. Reassuringly, the other 2% is categorised as "barren rock".
Annealing, in glassblowing and lampworking, is the process of heating, and then slowly cooling glass to increase "softness" (ductility) and durability. This process relieves the internal stresses, making the glass much more durable. Glass which has not been annealed will crack or even shatter when subjected to a relatively small temperature change or other shock. Sculpting hot blown glass. ... Lampwork glass beads. ... Ductility is the physical property of being capable of sustaining large plastic deformations without fracture (in metals, such as being drawn into a wire). ...
Glass is heated until the temperature reaches a stress-relief point, that is, the "annealing temperature" at which the glass is still too hard to deform, but is soft enough for the crystal structure of the material to flow together. The piece is then allowed to heat-soak until its temperature is even throughout. The time necessary for this varies depending on the type of glass and thickness of the thickest section. Glass can be made transparent and flat, or into other shapes and colors as shown in this sphere from the Verrerie of Brehat in Brittany. ... Fig. ... Stress is the internal distribution of force per unit area that balances and reacts to external loads applied to a body. ... In engineering mechanics, deformation is a change in shape due to an applied force. ...
The glass is then slowly cooled at a predetermined rate until its temperature is below a critical point when the internal stresses are balanced with the surface tension on the face of the glass. Then the temperature can safely be dropped to room temperature. After the annealing process the material can be cut to size, drilled or polished. Room temperature describes a certain temperature within enclosed space that is uses for various purposes by human beings. ...
Annealing, in metallurgy and materials science, is a heat treatment wherein the microstructure of a material is altered, causing changes in its properties such as strength and hardness. ... Float glass is made by melting raw materilas consisting of sand, limestone, soda ash, dolomite, iron oxide and salt cake. ... The materials definition of a glass is a uniform amorphous solid material, usually produced when a suitably viscous molten material cools very rapidly, thereby not giving enough time for a regular crystal lattice to form. ... The subject of optical fabrication and testing spans an enormous range of manufacturing procedures and optical test configurations. ...
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