STAINED GLASS & ART-GLASS TECHNOLOGY AND SAFETY INFORMATION

Art-Glass: every door and window comes standard with tempered glass for longevity and protection. WoodCiti® stained-glass consists of three independent layers of glass. The middle internal layer is an art-glass or stained glass. The two external layers are made from certified tempered glass.

Stained Glass	Tempered Glass	Art Glass

Artistic Glass is the colored glass used for making artistic decorative doors and windows through which light passes. Strictly speaking, all colored glass is “stained,” or colored by the addition of various metallic oxides while it is in a molten state; nevertheless, the term stained glass has come to refer primarily to the glass employed in making ornamental or pictorial windows. The singular color harmonies of the stained-glass window are due less to any special glass-coloring technique itself, however, than to the exploitation of certain properties of transmitted light and the light-adaptive behavior of human vision. Rarely equaled and never surpassed, the great stained-glass windows of the 12th and early 13th centuries actually predate significant technical advances in the glassmaker's craft by more than half a century. And much as these advances undoubtedly contributed to the delicacy and refinement of the stained glass of the later Middle Ages, not only were they unable to arrest the decline of the art, they may rather have hastened it to the extent that they tempted the stained-glass artist to vie with the fresco and easel painter in the naturalistic rendition of his subjects. Neither painting on stained glass nor its assembly with grooved strips of leading is an indispensable feature of the art. Indeed, the leaded door or window may well have been preceded by windows employing wooden or other forms of assembly such as the cement tracery that has long been traditional in Islamic architecture; and the single most important technical innovation in 20th-century stained glass, slab glass and concrete, is a variation on the earlier masonry technique.

Tempered Glass is a glass made at the glass factory, it is already pre-cut to size and when it breaks, it will not have sharp edges. Double insulated glass panels doors and window may consist of a double thickness tempered thick glass panel unit. We use tempered safety glass, to which we permanently fire the beautiful glass design. Next we permanently secure another piece of clear tempered safety glass behind this first piece. Toughened glass or tempered glass is a type of safety glass that has increased strength and will usually shatter in small, square pieces when broken. It is used when strength, thermal resistance and safety are important considerations. At home you are likely to find toughened glass in shower and sliding glass patio doors. In commercial structures it is used in unframed assemblies such as frameless doors, structurally loaded applications and any glass where these is a danger of human impact. Using toughened glass can pose a security risk in some situations due to the tendency the glass has to shatter utterly upon hard impact. Due to the balanced stresses in the glass, damage to the glass will eventually result in the glass shattering into thumbnail sized pieces. Although toughened glass is most susceptible to breakage via edge damage, breakage can also occur from impacts in the centre of the glass pane. Shattering may not happen when the damage originally occurs and can be triggered by a minor stress like heat or small impact that would not normally affect the toughened glass. If any toughened glass shows any damage it must be replaced.

Artistic Glass	Toughened Glass	Colored Glass

Toughened Glass must be cut to size or pressed to shape before toughening and cannot be re-worked once toughened. Polishing the edges or drilling holes in the glass is carried out before the toughening process starts. Also, ironically, the toughened glass surface is not as hard as annealed glass and is slightly more susceptible to scratching. Toughened glass is made from annealed glass via a thermal tempering process. The glass is placed onto a roller table, taking it through a furnace which heats it to above its annealing point of 600 °C. The glass is then rapidly cooled with forced draughts of air. This rapidly cools the glass surface below its annealing point, causing it to harden and contract, while the inner portion of the glass remains free to flow for a short time. The final contraction of the inner layer induces compressive stresses in the surface of the glass balanced by tensile stresses in the body of the glass. This compressive stress on the surface of the glass is typically as high as 50 MPa. It is this compressive stress that gives the toughened glass an increased strength. This is because any surface flaws tend to be pressed closed by the retained compressive forces, while the core layer remains relatively free of the defects which could cause a crack to begin. The pattern of cooling during the process can be revealed by observing the glass with polarized light, which shows the strain pattern in the glass. Though the underlying mechanism was not known at the time, the effects of "tempering" glass have been known for centuries.

Stained-Glass is made from small and medium size pieces of glass joined together. In general doors and windows made of colored glass. To a large extent, the name is a misnomer, for staining is only one of the methods of coloring employed, and the best medieval glass made little use of it. Colored glass as window decoration is of great antiquity in East Asia. Muslim designers fitted small pieces of it into intricate window traceries of stone, wood, or plaster, and this type of window mosaic is still in use. Colored glass was used in windows of Christian churches as early as the 5th century and pictorial glass as early as the 10th century. With the development of medieval architecture, stained glass assumed a unique structural and symbolic importance. As the Romanesque massiveness of the wall was eliminated, the use of glass was expanded. It was integrated with the lofty vertical elements of Gothic architecture, thus providing greater illumination. Symbolically, it was regarded as a manifestation of divine light. In these transparent mosaics, biblical history and church dogmas were portrayed with great effectiveness. Resplendent in its material and spiritual richness, stained glass became one of the most beautiful forms of medieval artistic expression. Stained Glass generally refers to glass that has either been painted and fired or colored by adding metallic salts during its manufacture and often both. The latter process is exemplified by, for example, the use of copper to produce green or blue glass or gold oxides to produce reds and oranges. Stained glass is an art and a craft that requires the artistic skill to conceive the design, and the engineering skills necessary to assemble the piece so that it is capable of supporting its own weight and surviving the elements. The process used in the 12th century has changed remarkably little even in modern times. The molten glass was annealed in a furnace to produce sheets of colored glass. This so-called 'pot-metal' glass was sometimes rather dark and, to overcome this, 'flashed glass' was made by dipping a lump of white glass on a blowpipe into a pot of red glass and then blowing. This provided sheets of glass with the thin layer of color. This could then be made bi-colored by grinding off some parts of the color. The colored glass was cut into different shapes with a 'grazing iron' and laid out on a table over the original design so that details of the drawing could be seen through it and painted with the oxide pigment on the surface. The pieces were then fired in a kiln. The oxides permanently fused with the glass to produce the painting, this is the derivation of the term "stained glass". The pieces were then re-assembled with strips of shaped lead, the glass being slotted into the grooves on each side. The pieces were then soldered together, and oily cement rubbed into the joints to make them watertight, and installed in a frame to create a window. Copper foil is now used instead of lead.

Insulated Glass	Laminated Glass	Safety Glass

Laminated Glass: WoodCiti® manufactures laminated glass over 20 mm thick. Triple insulated glass panels: our windows consist of a double or triple-thickness tempered and thick glass panel. The bevel glass panels use clear tempered glass on the inside, a beveled glass panel assembled using brass channel is in the middle of the glass unit, and obscure, tempered glass is on the outside. We can supply these glass panels with clear tempered glass on both sides (instead of the obscure glass) where privacy is not necessary. Laminated glass is a type of safety glass that holds together when shattered. In the event of breakage, it is held in place by an interlayer, typically of PVB, between its two or more layers of glass. The interlayer keeps the layers of glass bonded even when broken, and its high strength prevents the glass from breaking up into large sharp pieces. This produces a characteristic "spider web" cracking pattern when the impact is not enough to completely pierce the glass. Laminated glass is normally used when there is a possibility of human impact or where the glass could fall if shattered. Shop-front glazing and windshields are typically laminated glasses. The PVB interlayer also gives the glass a much higher sound insulation rating, due to the damping effect, and also blocks 99% of transmitted UV light. Using toughened glass on windshields would be a problem when a small stone hits the windshield at speed, if it were toughened and the stone hit with enough force the whole windshield would shatter into the small squares making visibility difficult and it would also be likely that the wind would blow the small squares into the driver and passengers.Laminated glass was invented in 1903 by the French chemist Edouard Benedictus, inspired by a laboratory accident. A glass flask had become coated with the plastic cellulose nitrate and when dropped shattered but did not break into pieces. Benedictus fabricated a glass-plastic composite to reduce injuries in car accidents. However, it was not immediately adopted by automobile manufacturers, and the first widespread use of laminated glass was in the eyepieces of gas masks during World War I. Today, laminated glass is produced by bonding two or more layers of ordinary annealed glass together with a plastic interlayer, usually polyvinyl butyral (PVB). The PVB is sandwiched by the glass which is passed through rollers to expel any air pockets and form the initial bond then heated to around 70 °C in a pressurized oil bath. The tint at the top of some car windshields is in the PVB. A typical laminated makeup would be 3 mm glass / 0.38 mm interlayer / 3 mm glass. This gives a final product that would be referred to as 6.38 laminated glass.

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