If you will follow European church making pattern then you will see, there window glasses and skylight glasses are full with patterns and colours. Those are called as stained glass. The Stained-glass term refers to coloured glass as a material or to works created from it. Throughout its thousand-year history, the term has been applied almost exclusively to the windows of churches and other significant religious buildings. Although traditionally made in flat panels and used as windows, the creations of modern stained glass artists also include three-dimensional structures and sculpture. Many foil glassworks and lamp glasses are found to be made with this.
Small piece of colour glasses is joined to make a pattern or a sculpture and the material of stained glass is glass that has been coloured by adding metallic salts during its manufacture. By joining small pieces patterns or pictures formed, held together (traditionally) by strips of lead and supported by a rigid frame. Painted details and yellow stain are often used to enhance the design. The term stained glass is also applied to windows in which the colours have been painted onto the glass and then fused to the glass in a kiln.
Patterned or stained glass, as an art and a craft, requires the artistic skill to conceive an appropriate and workable design, and the engineering skills to assemble the piece. A window must fit snugly into the space for which it is made, must resist wind and rain, and also, especially in the larger windows, must support its own weight. Many large windows have withstood the test of time and remained substantially intact since the Late Middle Ages. In Western Europe they constitute the major form of pictorial art to have survived. In this context, the purpose of a stained-glass window is not to allow those within a building to see the world outside or even primarily to admit light but rather to control it. For this reason, stained glass windows have been described as "illuminated wall decorations". The design of a window may be abstract or figurative; may incorporate narratives drawn from the Bible, history, or literature; may represent saints or patrons, or use symbolic motifs, in particular armorial. Windows within a building may be thematic, for example: within a church – episodes from the life of Christ; within a parliament building – shields of the constituencies; within a college hall – figures representing the arts and sciences; or within a home – flora, fauna, or landscape.
On the development of technology, during late medieval period glass factories were set up where there was a ready supply of silica, the essential material for glass manufacture. Silica requires a very high temperature to melt, something not all glass factories were able to achieve. Such materials as potash, soda, and lead can be added to lower the melting temperature. Other substances, such as lime, are added to rebuild the weakened network and make the glass more stable. Glass is coloured by adding metallic oxide powders or finely divided metals while it is in a molten state. Copper oxides produce green or bluish green, cobalt makes deep blue, and gold produces wine red and violet glass. Much modern red glass is produced using copper, which is less expensive than gold and gives a brighter, more vermilion shade of red. Glass coloured while in the clay pot in the furnace is known as pot metal glass, as opposed to flashed glass.
Some often-used types are cylinder glass or muff, crown glass, rolled glass, flashed glass and colours used are transparent, green glass, blue glass, red glass, yellow glass, purple glass and white glass.
The subject matter of the window is determined to suit the location, a particular theme, or the wishes of the patron. A small design called a Vidimus is prepared which can be shown to the patron. A scaled model maquette may also be provided. 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. 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 to whose memory the window is dedicated. In a window of a traditional type, it is usually left to 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 have 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 directly on the surface of a whitewashed table, which was then used as a pattern for cutting, painting and assembling the window. The cartoon is then divided into a patchwork, providing a template for each small glass piece. The exact position of the lead which holds the glass in place is also noted, as it is part of the calculated visual effect.
Each piece of glass is selected for the desired colour 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 using 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. 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. 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 coloured 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 coloured glass into sections. Scenes were painted onto glass panels of square format, like tiles. The colours were then annealed to the glass before the pieces were assembled. 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.
Today it can be found to used by people of upper class and represents a value of royalty. Modern use also derived many new feature and usability as home showcase article and exotic sculpture making, small statues and tableware also.