GLASSGLASS

Lenses that make objects look bigger or smaller are made by cutting glass. They help the human eye to see more than is possible by nature. Over the course of history, the improvements in the quality of glass and methods of production meant that we could see things that were invisible. Powerful telescopes enable the human eye to see far into the universe. And the lens in a microscope reveals a world too small to perceive with the naked eye. After the fall of Constantinople in 1204, craftsmen from the Byzantijn Empire took their knowledge of glass to Murano near Venice, where they perfected a production process in which with the addition of seaweed they could achieve glass of unparalleled clarity. In combination with the newly developed technique of blowing glass, it was possible to make curved glass. That laid the foundation for the development of the lens. At the start of the 17th century, two men from Middelburg vied with each other to invent the telescope: eyeglass maker Hans Lippershey and Zacharias Jansen, who later contributed to the invention of the microscope. Over the centuries the instrument was perfected via figures like Galileo, who was the first person to use the telescope to look into outer space. The gaze reached further and further. Progress occurred in fits and starts. It was not until John Dolland in about 1758 had combined crown glass and flint glass in his design of the telescope that the discoloration that had clouded the view up to then finally disappeared. The limit now seems to have been reached. Only a new chemical composition can increase the quality of glass spectacularly, and thus our ability to see even further.

The chemist's laboratory is full of glass, a material eminently suitable for preserving, mixing, heating and cooling chemical substances, because it does not react with them and, moreover, is both gas-proof and liquid-proof. As a transparent material, all processes taking place in the flasks, dishes and test tubes are immediately visible. The chemical recipe for glass has always been shrouded in mystery, as though it were a form of alchemy. The composition of the so-called 'mix' was, and is, a closely guarded secret among glassmakers and manufacturers. Small variations in the proportions of basic materials such as sand, lime and soda make a big difference in the quality and appearance of the glass. When the German chemist Otto Schott added the element borium to the mixture in the late 19th century, he created glass that was highly resistant to rapid heating and cooling. Laboratories could now avail of heat-resistant test tubes, which heralded a revolution in various branches of science. Working with glassblowers, scientists could relatively easily make standard sizes of glass vessels suitable for their experiments. That resulted in new discoveries we are still familiar with to this day. For example, the fluorescent lamp - or what we call strip lighting - is directly descended from a discovery by Heinrich Geissler, who midway through the 19th century succeeded in generating a blue glow inside a tube filled with gas. And fifty years later came the invention of the Crookes tube, a gas discharge tube in which radioactive material creates a green light as soon as a strong electrical charge is conducted through it. For a long time, this invention made by the British chemist William Crookes remained a curiosity, until the discovery that the cathode ray tube could be applied in the X-ray tube (which we have used ever since to examine the body) and the picture tube (which could capture the world in a television).

Although developments in glass fibre certainly rank among the most recent innovations with the material, the technique of making extremely thin glass fibres goes back much earlier, and has been mastered on the island of Murano near Venice since the 17th century. A well-known application is the Venetian millefiori technique. Thin strands of coloured glass are rolled together, heated and stretched to form a glass cane. The ends reveal the multicoloured pattern of strands. The cane is then cut into discs and used as decoration in beads, jewellery and utensils. The invention of synthetic materials strengthened with spun glass like fibreglass resulted in a material that was anything but fragile and transparent. An extremely effective application of glass fibre is the septic tank: light, strong and unaffected by the chemical processes taking place within. While carbon fibres have now replaced glass fibres in many products, they are still used for this tank. Glass fibre did, however, lead to breakthroughs in a totally different field. The endoscope, originally devised to explore parts of machines that were difficult to access, was almost immediately employed by enterprising surgeons to examine the throat and intestines. Today it is a vital instrument in medical practice. If light could be transmitted through glass fibre, then so too could data. The American naturist Charles Kao formulated the requirements to facilitate communication by transmitting light through optical fibres. The purity of the glass was the most important challenge for science. Taking pure rock-crystal and forming it into thread using a refined technique eventually paved the way for the internet, with its infrastructure of high- standard glass fibre cables. An unexpected by-product of this technique is the so-called 'glass fibre lamp', designed in the early stages of glass fibre mass production as a way of making use of the vast amounts of fibre that weren't quite pure enough.

Curators J.H. In 't Veld and T.G. Koehorst compiled a descriptive and illustrated catalogue of the exhibition, embellished with more than one hundred and sixty pictures.

• Download: catalogue 'Glass Engine of Progress'