)are made by heating sand silica until it melts into a liquid state. the melted glass can then either be shaped by ) the liquid glass or by pouring the melted glass into a mold. the shape and size of the finished piece depends on the tools and method used by the artist.
a. (1) glass pieces of art; (2) condensing
b. (1) fiber crafts; (2) hammering
c. (1) glass crafts; (2) blowing
d. (1) fiber pieces of art; (2) shaping

c. (1) glass crafts; (2) blowing

Explanation:

Glass is manufactured from a complex mixture of vitrifying compounds, such as silica, fluxes, such as alkalis, and stabilizers, such as lime. These raw materials are loaded in the bucket oven (continuous production) by means of a hopper. The oven is heated with gas or oil burners. The flame must reach a sufficient temperature, and for this the combustion air is heated in recuperators built with refractory bricks before it reaches the burners. The oven has two recuperators whose functions change every twenty minutes: one is heated by contact with the burning gases while the other provides the heat accumulated to the combustion air. The mixture melts (melting zone) at about 1,500 ° C and advances towards the cooling zone, where annealing takes place. At the other end of the oven a temperature of 1,200 to 800 ° C is reached. The glass thus obtained is shaped by lamination (as in the above scheme) or by another method.

After careful measurement and preparation, the raw materials are mixed and subjected to an initial fusion before applying all the heat necessary for vitrification. In the past, the fusion was carried out in clay (mud) containers that were heated in ovens fed with wood or coal. Still today, refractory clay containers are used, containing between 0.5 and 1.5 tons of glass, when relatively small amounts of glass are needed to work by hand. In modern industries, most of the glass melts in large cauldrons, first introduced in 1872. These cauldrons can contain more than 1,000 tons of glass and are heated with gas, fuel oil or electricity. The raw materials are introduced continuously through an opening located at one end of the cauldron and the molten glass, refined and tempered, exits at the other end. In large crucibles or retention chambers, the molten glass is brought to the temperature at which it can be worked, and then the vitreous mass is transferred to the molding machines.

Molded

The main methods used to mold the glass are casting, blowing, pressing, stretching and rolling. All these processes are old, but have undergone modifications to produce glass for industrial purposes. For example, centrifugal casting processes have been developed in which the glass is forced against the walls of a rapidly rotating mold, which allows to obtain precise forms of low weight, such as television tubes. Automatic glass blowing machines have also been developed.

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