Post 393 – by Gautam Shah
A bevelled glass is made by dressing or grinding the edge or sections of a design with a slope, chamfering or an angled edge to create special effects. The edge dressing creates a prism like effect and alters the way light refracts while passes through the glass or reflect of the surface. Bevelling splits the light into unusual patterns including a rainbow of colours. Bevelled glass is installed in doors and windows to add dynamism to daylight illumination of a room. There were few other techniques of treating the glass, like fire finish, etc. for special lighting effects. These were devised as soon as glass for windows matured in quality.
Early glass, such as of Romans was mainly in the form of fuzzy disks that were inserted in terraces, arched barrels and domed roofs for illumination of interiors. These were very fuzzy or low intensity illuminating devices. Glass disks were polished to reduce the fuzziness due to the surface or casting related impurities. Irregularities related to manufacturing were of several types, such as the colourant contamination, bubbles or casting -moulding methods. In spite of grinding, all of these could not be eliminated so easily. Clear glass panes of some translucency were first made by blowing it to thin walled cylinders or bulbs, then cut and flattened. These, 3rd C, methods gave clearer glass, because it was of a thinner body and larger in size than the cast disks. These panes were placed in structured punctures as a fixed panels. The glass was more translucent but visually very hazy.
The hazy glasses, however, provided wonderful glow to interiors. The costs were prohibitive due to the rarity, high cast of installation and need for frequent replacement. The ‘daytime glowing glass’ had inconsistent levels of impurities. An opening with several such panes would look fairly patchy, but this was camouflaged with glass colourants. The colourants or staining compounds offered a palette of colours.
The stained glass provided a daytime glow to the interiors, but it was not a working level of illumination. The increased openings’ size and larger glazed extent provided sufficient interior illumination on clear day and for few hours of daytime exposure. This problem was solved by using lighter tones of colours than the ‘pot’ glass, and by leaving substantial sections of image backgrounds (other than the holy images) of colourless glass.
The Church interiors began to use glasses of lighter colours and plain glasses. These reduced the overpowering effect of colour in the interior space, allowing gilding and other ornamental details to be seen and also permitting the building to glow on outside, at night with interior lighting. It also allowed the reappearance of wall paintings, and colouring of architectonic interior elements.
The glass as produced by cylinder or crown method was hazy, with marks of flutes but fairly colourless. It was of small sized panes. The panes were joined together with lead cames. The lead cames which earlier, marked the free flowing strong defining lines of the image, were now grid forms. American colonial sash windows represent the classic grid. The glass, of the industrial revolution period had manufacturing defects such as lines, flutes and rings. It was not possible to view the exterior as one large picture across the leads. The leads’ grid however imposed a visual discipline, rest of the disguising was achieved by thin see-through curtains and by painting the windows white.
During the industrial revolution period clear quality glasses of very large sizes began to be available. Very large and absolutely flawless, water white clear glass had its own problems of acceptance. It was too clear for the interior privacy, and provided no framing or visual masking over the view to outside. The problem was partly solved by installing curtains with both sides having visual appeal. Its appearance was rather too consistent.
Some longed for the dynamism of variegated glass and visual masking. These two elements were provided by engraving and etching the glass surface with textures and patterns. To this was added the technique of glass bevelling. Glass bevelling is done in THREE basic manners. Edges of the glass panes are bevelled, very much like the wood panels in a door. Glasses are bevelled grooved by engraving. And the glasses are overlayed by smaller pieces of bevelled edged shapes.
Bevelled glasses are used for doors, windows and partition panels. The bevelled glass is often additionally treated with grinding, etching, engraving, and painted staining work. Bevelled glass was favoured as it provided occlusion for privacy and isolation, but nowadays window glasses with various levels of tinting, metallic sprays, polyester films, etc. provide the same facility. Bevelled glass is still unrivalled in terms refracting the light in a spectrum of colours and dynamism.