Producing a stained glass panel is a long, expensive and complex business.If the panel is architectural, that is making up an integral part of the building, there will be safety considerations such as the strength and size of glass and lead, as well as internal and external strengthening bars.
The design of any stained glass panel, whether large or small, must be fluid, coherent and above all, workable in glass. Glass is not a solid material, it is a supercool liquid whose behaviour and properties very much resemble those of ice. The design problems presented by such a material can often be difficult and complicated.
Once a basic design is agreed with the clients, usually through drawings and watercolour sketches, a cartoon is drawn up on translucent paper. This cartoon or cut line is a complete two-dimensional representation of the actual panel: the measurements, line thickness and design integrity must be absolutely accurate otherwise all sorts of problems can arise later with assembly, fitting and durability. Some designs require the use of glass paints and stains such as silver stain, in which case a glass kiln will be needed. Parts of the panel may also need to be etched using either hydrofluoric acid or sandblasting.
Most glass can be cut and shaped nowadays by using an oil-fed tungsten carbide wheel; with patience and experience, very delicate and intricate cutting can be achieved. The best oil-fed glass cutters come from Korea, Japan and Germany. As the pieces of glass are cut, they are placed on a glass easel (a large piece of clear glass upon which the cartoon has been drawn), using plasticine or blue tack. Using an easel helps the artist see the development of the design and the play of colours and line. It also keeps all the cut pieces secure and out of the way until they are needed.
When all the glass pieces have been accurately cut the process of leading up can begin.Lead came, as the strips are called, come in several different widths and thicknesses. Usually a wide flat lead is fitted to the borders after which the very delicate and exact business of leading the whole panel starts.The lead strips must be cut very precisely and great care must be taken to ensure that the glass pieces fit snugly and that the lead joints are as close and tight as possible.
Soldering follows: using a gas or electric soldering iron, a small amount of solder must be smoothly applied to each lead joint on both sides of the panel. Soldering is a very tricky skill which can take some years to develop.The panel will then need to be scrubbed clean of flux and dirt before being cemented. Some stained glass artists use specially prepared lead putty while many still use the traditional leaded light cement. As with all stained glass processes, cementing is slow and labour-intensive. The cement or putty must be forced into the leaves of lead on both sides of the panel. Once this is done a great deal of cleaning and polishing is required before the panel is ready for installation. If done correctly, the panel is then remarkably strong, weather-proof and durable.
Although all the materials required for stained glass are frighteningly expensive and although the processes are long, difficult and labour-intensive, well-made stained glass will last for centuries if properly cared for. The colours do not fade; the light, colours and atmosphere are constantly changing with day and night as well as the progress of the seasons.