Stained Glass

A large Perpendicular style Gothic window of eight lights in Canterbury Cathedral, c. 1400, which contains medieval glass.The term stained glass can refer to coloured glass as a material or to works made from it. Throughout its thousand-year history, the term has been applied almost exclusively to the windows of churches and other significant 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.Modern vernacular usage has often extended the term “stained glass” to include domestic leadlight and objets d’art created from lead came and copper foil glasswork exemplified in the famous lamps of Louis Comfort Tiffany.As a material stained glass is glass that has been coloured by adding metallic salts during its manufacture. The coloured glass is crafted into stained glass windows in which small pieces of glass are arranged to form patterns or pictures, 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.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 anything goes diet 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 non-figurative 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.Glass factories
The first industrial complex for glass and pottery production was built in Ar-Raqqah, Syria, in the 8th century. Extensive experimentation was carried out at the complex, which was two kilometres in length, and a variety of innovative high-purity glass were developed there. Two other similar complexes have also been discovered, and nearly three hundred new chemical recipes for glass are known to have been produced at all three sites
The first glass factories were thus built by Muslim craftsmen in the Islamic world. The first glass factories in Europe were later built in the 11th century by Egyptian craftsmen in Corinth, Greece
[edit]Clear, colourless and high-purity glass
The earliest examples of clear, colourless and high-purity glass were produced by Muslims in the 9th century, such as the quartz glass invented by Abbas Ibn Firnas. The Arab poet al-Buhturi (820-897) describes the clarity of such glass as follows:
“Its colour hides the glass as if it is standing in it without a container.”
[edit]Coloured and stained glass
Stained glass was first produced by Muslim architects in Southwest Asia using coloured glass rather than stone. In the 8th century, the Arab chemist Jabir ibn Hayyan (Geber) scientifically described 46 original recipes for producing coloured glass in Kitab al-Durra al-Maknuna (The Book of the Hidden Pearl), in addition to 12 recipes inserted by al-Marrakishi in a later edition of the book.
[edit]Glass production
From the 10th or 11th century, when stained glass began to flourish as an art, glass factories were set up where there was a ready supply of silica, the essential material for glass manufacture. Silica requires very high heat to become molten, something furnaces of the time were unable to achieve. So materials needed to be added to both modify the silica network to allow the silica to melt at a lower temperature (potash, soda, lead), and then to rebuild the weakened network (lime) and make the glass more stable. Glass is colored by adding metallic oxides while it is in a molten state. Copper oxides produce green, cobalt makes blue, and gold produces red 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 colored while in the clay pot in the furnace is known as pot metal glass, as opposed to flashed glass.
Cylinder glass or Muff Using a blow-pipe, a “gather” (glob) of molten glass is taken from the pot heating in the furnace. The gather is formed to the correct shape and a bubble of air blown into it. Using metal tools, molds of wood that have been soaking in water, and gravity, the gather is manipulated to form a long, cylindrical shape. As it cools, it is reheated so the manipulation can continue. During the process, the bottom of the cylinder is removed. Once brought to the desired size it is left to cool. One side of the cylinder is opened. It is put into another oven to quickly heat and flatten it, and then placed in an annealer to cool at a controlled rate, making the material more stable. “Hand-blown” cylinder (also called muff glass) and crown glass were the types used in ancient stained-glass windows.
Crown glass This hand-blown glass is created by blowing a bubble of air into a gather of molten glass and then spinning it – by hand or on a table that revolves rapidly like a potter’s wheel. The centrifugal force causes the molten bubble to open up and flatten. It can then be cut into small sheets. Glass formed this way can be both colored and used for stained-glass windows, or uncolored as seen in small paned windows in 16th and 17th century houses. Concentric, curving waves are characteristic of the process. The center of each piece of glass, known as the “bull’s-eye”, receives less force during spinning, so it remains thicker than the rest of the sheet. It also has the distinctive lump of glass left by the “pontil” rod, which holds the glass as it is spun out. This lumpy, refractive quality means the bulls-eyes are less transparent, but they have still been used for windows, shokz guide both domestic and eccliesiastical. Crown glass is still made today, but not on a large scale.
Rolled glass Rolled glass (sometimes called “table glass”) is produced by pouring molten glass onto a metal or graphite table and immediately rolling it into a sheet using a large metal cylinder, similar to rolling out a pie crust. The rolling can be done by hand or machine. Glass can be “double rolled”, which means it is passed through two cylinders at once (similar to the clothes wringers on older washing machines) to yield glass of a specified thickness (typically approximately 1/8″). Glass made this way is never fully transparent, but doesn’t necessarily have much texture. It can be pushed and tugged while molten for certain effects. For distinct textures the metal cylinder can be imprinted with a pattern that is pressed into the molten glass as it passes through the rollers. The glass is then annealed. Rolled glass was first commercially produced around the mid-1830s and is widely used today. It is often called intermittent fasting cathedral glass, but this has nothing to do with medieval cathedrals, where the glass used was hand-blown.
Flashed glass Architectural glass must be at least 1/8 of an inch to survive the push and pull of typical wind load. In order to make red glass, the ingredients used must be of a certain concentration, or the color won’t develop, but the resulting color is so concentrated, that if a sheet were made that is 1/8” thick, little light could actually pass through it – it would look black. So another method is usually used for making red glass, where most of the body of the glass is clear or a colored tint. This lightly-colored molten gather is dipped into a pot of molten red glass, forming a laminate that is then blown into a sheet of glass using either the cylinder (muff) or the crown technique as described above. Once the solution was found for making red glass, other colors were also made this way. A great advantage is that the double-layered glass can be engraved or abraded to reveal the clear or tinted glass below. The guitar scales method allows rich detailing and patterns to be achieved without needing to add more lead-lines, giving artists greater freedom in their designs. A number of artists have embraced the possibilities flashed glass gives them. For instance, 16th century heraldic windows relied heavily on a variety of flashed colors for their intricate crests and creatures. In the medieval period the glass was “abraded” (ground off), later hydrofluoric acid was used to remove the flash in a chemical reaction (a very dangerous technique) and in the 19th century sandblasting started to be used.
Modern production of traditional glass There are a number of glass factories, notably in Germany, USA, England, France, Poland and Russia, which produce high-quality glass, both hand-blown (cylinder, muff, crown) and rolled glass (cathedral and opalescent). Modern stained-glass artists have a number of resources to use and the work of centuries other artists to dialogue with as they continue the tradition, but in new ways.
[edit]Creating stained glass windows
The first we buy any house 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 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 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 favoured 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 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 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 sell house fast, 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.
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