In the glass works we must not forget the great skill and operability of the glass artisans who are superbly able to decorate the glass in real works of art.
Here are some techniques:
Engraving, Etching, Sandblasting.
Engraving
The engraving consists of a thin scratch with a tip of a material harder than glass (vidiam steel, corundum, diamond) on the surface.
It is a very ancient technique that has been applied to glass as a derivation from semi-precious stones.
The groove appears opaque and in this way you can draw designs or decorations or simply write on the glass.
To engrave hard bits are used, very small wheels and hard rotating bits applied to a drill similar to that of the dentist.
Many glass masters and companies sign their objects with this technique.
The incision (or carving) on the wheel, on the other hand, consists in removing surface glass by means of abrasive powders applied to wheels that rotate at great speed. The result is a bas-relief work where the carved depressions create figures, decorations, etc.
The process includes three successive operations: the actual carving with coarser abrasives that creates the rough work, an intermediate step with finer abrasive, and the final polishing (if required) with cerium oxide applied on soft supports such as cork, plastics or felt cloths.
This last step makes the surface perfectly shiny, eliminating the opacity left by the previous steps.
Acidation
When a glass is immersed in a mixture of hydrofluoric and sulfuric acid, surface corrosion occurs.
The real corrosive is hydrofluoric acid, sulfuric acid dissolves the insoluble fluosilicates that are formed and which would tend to deposit on the surface.
The parts of the object that must not come into contact with the acid are covered with waterproof material (waxes or fats) so that the acid can act only on the selected and uncovered areas.
More or less deep etching is obtained on the basis of the concentration and ratio between the two acids, the temperature and contact time of the glass with the acid bath.
Sandblasting
The glass surface can be attacked and then sanded also by the effect of a jet of sand pushed by the compressed air against the surface.
The fineness of the grinding depends on the type and violence of the jet and the grain size of the sand.
It is a cheaper and more ecological method than acid etching.
The parts of the surface that must not be sanded are protected with metal masks in which the designs to be reproduced on the glass are cut out.
Source:
Glassway.vda.it
