We tend to judge glass by how much we don’t see it. As big as possible, uninterrupted surfaces of nothing. But glass is matter. Glass has color. Glass has texture. Glass has the power to concentrate or disperse light. Czech glass artists Stanislav Libenský and Jaroslava Brychtová (collaborated from 1962-2002) beautifully articulate the architectural potential of glass.

The craft of prismatic glass in architecture has its origins in the design of deck lights for ships in the 17th century. For fire safety, prismatic glass was used to replace the use of oil lamps below deck. In 19th century New York and Chicago glass prisms were integrated in pavements to light souterrains below, as electricity was expensive. There was a period in architectural history, in the interbellum, just before the invention of float glass, when prismatic glass building bricks were a topic of innovation. Architects like Frank Lloyd Wright, Hendrik Petrus Berlage, Piet Zwart and Gustave Falconnier used techniques of glass blowing, pressing and casting to develop prismatic bricks, to let more light into buildings with less material. Fantastic colorful designs were produced by the Royal Glassware in Leerdam and Saint-Gobain Glassware in Paris.

In current times, there is a renewed role for recycled glass, which needs much lower temperature to be shaped into new glass than the virgin materials. However, the ‘impurities’ that the glass contains due to coatings etc, gives them specific colours, for example a high iron content makes the glass greener. Using beer bottles for building was famously done by John Habraken for the World Bottle by Heineken, unfortunately never taken into mass production.

Currently, la-di-da is doing some testing of its own, generously supported by Stimuleringsfonds Creative Industrie at MAKE Eindhoven to see if reused glass can be formed into prismatic tiles through casting, slumping, blowing and milling. For the process of casting, glass is cleaned, sorted by colors (it is important not two different types of bottles are mixed), crushed (a consistent size of cullet is needed), and then fired at 960 degrees. The plaster molds are made from 3D prints, each form is cast twice (once with white float glass, once with green bottle glass). The higher the iron content, the less translucent the shape. The fused points remain quite visible, reducing the prismatic effect. In order to achieve this with casting, a temperature of 1160 must be reached. For slumping, two different thicknesses of discarded floatglass are cleaned and cut to size (square and circle), and fired at 760 degrees. The effect of dogboning (glass approaching a 6mm thickness during fusing) is less observed at lower temperatures. Thinner glass tends to warm up more around the edges and that might mean it stretches itself over a form, sometimes creating air pockets. The molds are CNC milled from massive blocks of plaster. In the future, we aim to transform the CNC milling machine into an aquarium to make more shallow tests for milling the glass! la-di-da is also collaborating with MAKE to make a bronze mold for glass blowing that can be reused multiple times.