Creating stained glass windows

• The first stage in the production of a window is to make, or acquire from the architect or owners of the building, an accurate template of the window opening that the glass is to fit.
• The subject matter of the window is determined to suit the location, a particular theme, or the whim of the patron. A small design called a Vidimus is prepared which can be shown to the patron.
• A traditional narrative window has panels which relate a story. A figurative window could have rows of saints or dignitaries. Scriptural texts or mottoes are sometimes included and perhaps the names of the patrons or the person as whose memorial the window is dedicated. In a window of a traditional type, it is usually at the discretion of the designer to fill the surrounding areas with borders, floral motifs and canopies.
• A full sized cartoon is drawn for every "light" (opening) of the window. A small church window might typically be of two lights, with some simple tracery lights above. A large window might have four or five lights. The east or west window of a large cathedral might have seven lights in three tiers with elaborate tracery. In Medieval times the cartoon was drawn straight onto a whitewashed table, which was then used for cutting, painting and assembling the window.
• The designer must take into account the design, the structure of the window, the nature and size of the glass available and his or her own preferred technique. The cartoon is then be divided into a patchwork as a template for each small glass piece. The exact position of the lead which holds the glass in place is part of the calculated visual effect.
• Each piece of glass is selected for the desired color and cut to match a section of the template. An exact fit is ensured by grozing the edges with a tool which can nibble off small pieces.
• Details of faces, hair and hands can be painted onto the inner surface of the glass in a special glass paint which contains finely ground lead or copper filings, ground glass, gum arabic and a medium such as wine, vinegar or (traditionally) urine. The art of painting details became increasingly elaborate and reached its height in the early 20th century.
• Once the window is cut and painted, the pieces are assembled by slotting them into H-sectioned lead cames. The joints are then all soldered together and the glass pieces are stopped from rattling and the window made weatherproof by forcing a soft oily cement or mastic between the glass and the cames.
• Traditionally, when the windows were inserted into the window spaces, iron rods were put across at various points, to support the weight of the window, which was tied to the rods by copper wire. Some very large early Gothic windows are divided into sections by heavy metal frames called ferramenta. This method of support was also favored for large, usually painted, windows of the Baroque period.
• From 1300 onwards, artists started using silver stain which was made with silver nitrate. It gave a yellow effect ranging from pale lemon to deep orange. It was usually painted onto the outside of a piece of glass, then fired to make it permanent. This yellow was particularly useful for enhancing borders, canopies and haloes, and turning blue glass into green glass for green grass.
• By about 1450 a stain known as Cousin's rose was used to enhance flesh tones.
  In the 16th century a range of glass stains were introduced, most of them colored by ground glass particles. They were a form of enamel. Painting on glass with these stains was initially used for small heraldic designs and other details. By the 17th century a style of stained glass had evolved that was no longer dependent upon the skilful cutting of colored glass into sections. Scenes were painted onto glass panels of square format, like tiles. The colors were annealed to the glass and the pieces were assembled into metal frames.
• In modern windows, copper foil is now sometimes used instead of lead. For further technical details, see Lead came and copper foil glasswork.
  In the late 19th and 20th centuries there have been many innovations in techniques and in the types of glass used. Many new types of glass have been developed for use in stained glass windows, in particular Tiffany glass and slab glass.
• A method used for embellishment and gilding is the decoration of one side of each of two pieces of thin glass which are then placed back to back within the lead came. This allows for the use of techniques such as Angel gilding and Eglomise to produce an effect visible from both sides but not exposing the decorated surface to the atmosphere or mechanical damage.