Traditional stained-glass designs are created today with the same artisanal techniques as centuries ago. The creation of a stained-glass window can take a few days, or even years of work, depending on the complexity of the project.
Stained glass windows are formed from ancient, hand- blown stained glass produced in specialised glass mills, where it is brought into a molten state and coloured with metal oxides in special tanks.
The artisans take up a portion of molten glass with the extremity of a glassblowing pipe and blow a bubble, which they will afterwards shape into a cylinder. After cooling, the cylinder is cut horizontally along its “spine” and then placed in a kiln. There, under the influence of temperature, the cylinder straightens into a glass sheet.
Such hand-made glass sheets are brought to our Workshop, where they are cut with a diamond tool by experienced stained-glass masters. Each glass element so obtained is then carefully polished on all sides.
If the design requires it, individual glass sections are painted.
A contour paint is applied first. Afterwards various paint layers are applied consecutively, thanks to which a chiaroscuro modelling effect is obtained. The procedure is completed with glaze paints. Each paint layer is thermically fixed in the kiln with a temperature of between 600° and 800° C.
Sometimes, in order to obtain the proper effect, single glass elements require several various firing stages in order to fix one by one all the paint layers.
Another technique used to create stained-glass windows is etching.
In order to work with such a technique, the artist needs to use double-layered glass – a special type of glass which consists of two layers, each one presenting a different colour (these layers are combined at the glass mill). Such glass can be partially treated with acids: the areas subjected to this treatment will reveal the glass layer beneath, obtaining a dual-colour and three-dimensional effect on a single glass sheet. It is a very noble technique and this type of glass is itself extremely rare and expensive to manufacture.
When all the glass sections are ready, we can proceed with framing. The most traditional framing technique for stained glass, which dates back to the Middle Ages, involves the use of lead profiles, which are long lead strips, whose cross section is in the shape of an “H”.
Glass elements are inserted in those profiles. Finally lead profiles’ junctures are soldered with tin, which completes the framing procedure. In order to seal the stained-glass window free spaces are filled with a special putty, which makes the stained-glass window rigid.
In the case of smaller decorative stained-glass objects it is possible to make use of a technique invented at the beginning of the 20th century by the artist Louis Comfort Tiffany. It consists of framing stained glass in copper strips which are going to be soldered not only at the junctures, but along their whole length, so to cover them with tin completely.
Traditionally made stained-glass windows have been thrilling us for centuries, never losing their colours, their contours, still delighting us today with their multitude of light reflections.