Technological process of glass.
The technological process consists of many operations and activities, during which appropriate temperature conditions should be maintained, atmosphere and gas pressure. Temperature is the determining factor on the melting efficiency, the atmosphere affects cleanliness, pressure and the homogeneity of the glass mass. The team of operations and activities of the technological process belong to: preparation of a glass set, melting, forming products, annealing of the formed products and finishing.
Operation preparation of a glass kit covers:
- weighing raw materials,
- mixing of raw materials,
- briquetting (molding in the form of cubes with a little water),
- delivery of a set for blast furnaces.
Activities melting consists in converting the glass batch by temperature into an amorphous glass mass as a result:
- dehydration of the glass set,
- melting of silica (glass-forming raw material),
— accumulation of CO gas bubbles2, SO2, THE2, as products of chemical reactions,
- clarification of the glass mass, that is, removing gas bubbles,
— homogenization of the mass by mixing and gradual cooling.
Melting, depending on the type of glass obtained, takes place at a temperature of 900-1200 ° C and largely determines its quality. As a result of these activities, the glass mass achieves the appropriate ductility (viscosity) and temperature for the manufacture of glassware.
Glass products are formed by blowing them out, extrusion, ironing, hauling, rolling and casting. The products are shaped manually, mechanically or automatically. Blow molding and extrusion methods are widely used in the manufacture of cookware, glass instruments, haberdashery, which can be given various shapes and sizes. The drawing and rolling methods are mainly used for the production of flat glass.
Stress relieving the formed products is intended to remove significant internal stresses in the glass, formed during rapid cooling during shaping of glassware. The products are reheated to the optimum temperature (410-730°C), near the softening point, and then cooled slowly under control to ambient temperature. The properties and structure of the glass are uniform throughout the thickness of the product.
Finishing glass products involves many processes, which are to ensure the final functional characteristics of the product. They are obtained by grinding the edges, polishing the surface, possible decoration of the product.
Some glassware, especially table and fancy glassware, in the final stages of production, they are decorated, in order to obtain a finished product with the highest aesthetic values:
• carving is the oldest method of glass decoration, consisting in making deep grooves, making up a specific composition, with grinding wheels or by changing the original shape, just like carving wood or stones;
• engraving (engraving) is a special type of carving; with this method, much more precise patterns and decorations can be obtained through very small and shallow grooves, called scratches;
• the properties of hydrofluoric acid are used in digestion, which dissolves (digesting) glass; the surface of the product is covered with a protective paraffin layer (beeswax, stearins, therapy) and in it he will scratch elements of decoration, and then the entire product is immersed in the HF acid; this is how permanent lines and ornaments are created; etching is also used to remove sharp edges of grooves after carving and engraving;
• matting, are treatments aimed at creating a layer that diffuses light evenly and causes the phenomenon of opacity; glass loses its shine and becomes dull;
• painting consists in covering the surface of glassware with colorful drawings made with paints and gold;
• iridescence is a method that allows to obtain glass surfaces shimmering with the colors of the rainbow; such effects are obtained by depositing heated tin and titanium salts on the surface of the articles, as a result a thin layer is formed which is quite abrasion resistant;
• peeling with glue, the so-called. "Frost flowers" - the previously dull surface is covered with melted glue, which completely fills in minimal scratches and dents; the glue shrinks as it dries, which breaks and breaks off with splinters of glass.
Depending on the type of decorative elements, glass products have been divided and classified into appropriate decoration classes.