It was a challenge to learn how to produce large glass panels completely permeated with colour by using metal oxides. The knowledge of the glass formulae used in the gothic cathedrals, such as Notre Dame in Chartres, France, with its large multi-coloured windows, has been lost for the most part, or is strictly kept secret in a few glass makers guilds. We had to discover what qualities the raw materials need to have in order for them to lead to the required therapeutic effect, as well as how the different substances react in the glass melting, pouring, and cooling processes, ourselves.
The sculptor Lucien Turci, took on the task of working that out. With the help of the glass blower Florian Harling, he set up a workshop with a melting furnace, a movable pouring table, and the other necessary equipment. This completed, he began researching glass formulae. He intensively investigated the substances required in glass making: quartz, chalk, soda, and potash. These are the main substances which, in particular proportions and under very specific conditions, were combined with metal oxides, such as iron or copper oxides. He studied the aspects of the melting process, the furnace temperature and air supply, and the cooling process once the glass had been poured. He carried out every step multiple times in order to learn how to repeat changes that had occurred.
The process of mixing the base substances must be performed very carefully in glass making - later colour development depends upon it. Each colour tone requires a different mixture. Once the melting furnace has reached a temperature of approximately 1350 degrees Celsius, the melting pot is filled with the mixture of substances and placed in the furnace. After a number of hours, the substances have completely melted. While maturing, the liquid glass is occasionally stirred, which makes it purer and more homogenous. After 24 - 48 hours in the furnace, the liquid glass is poured. Two people are required for the pouring, one removes the extremely hot clay pot out of the furnace and pours the liquid glass mixture onto the pouring table. The second person pushes the pouring table carefully and evenly beneath the tipped clay melting pot, so that the liquid glass can spread evenly and without bubbles. The glass pouring must be accomplished very quickly, as the liquid glass mixture hardens within 2 - 3 minutes. Directly following pouring, the already hardened glass panel is placed in the cooling oven, where it stays approximately two days on average. The metal oxide colours only appear once the panel has completely cooled.
This process has made it possible for Lucien Turci to produce glass panels 110 cm x 65 cm x 1.8 cm in size: iron glass panels in sombre tones from blue to blue-green, olive green, matt yellow and brown; copper glass panels in turquoise blue and red tones, and gold glass panels in light-filled hues from delicate peach blossom to magenta, red, purple, and blue. Silver, sulfur and the iron-related metals cobalt, nickel and manganese have also resulted in beautiful coloured glass.