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Types of glass
There are many different types of glass. They differ in terms of their chemical composition, the method used to produce them or their processing behaviour. Generally, they are categorised according to their chemical composition. A differentiation is made between
soda-lime glass, lead glass and borosilicate glass. These three types of glass make up around 95 percent of the cullet glass used in the production process. The remaining 5 percent of glass is special-purpose glass.
Soda-lime glass is the glass produced in by far the largest quantities of all mass produced glass types. As the name indicates, the main constituents in addition to sand are soda and lime. A typical soda-lime glass contains 71 to 75 percent sand (SiO2), 12 to 16 percent sodium bicarbonate (Na2O), 10 to 15 percent lime (CaO) and small quantities of other substances such as dyes. Soda-lime glass is used to make bottles, food jars, simple drinking glasses and sheet glass products. Soda-lime glass is light permeable and has a smooth, fine-pored surface, making it easy to clean. It also expands very quickly under the influence of heat so care should always be taking when putting hot water into a soda-lime glass container.
Crystal glass looks beautiful when cut as a result of its high refraction index. It has a far higher density than soda-lime glass. In our everyday lives, we use crystal glass to make drinking glasses, vases, bowls, ashtrays and decorative ornaments. Its composition is 54 to 65 percent sand, 13 to 15 percent alkali oxide and several other oxides. Glass containing more than 18 percent lead oxide is also known as lead crystal glass. However, lead oxide is hardly used today in glass production. Crystal glass only accounts for less than 0.5 percent of total tableware glass production in Germany.
Special glass is used for special technical and scientific applications. Its composition can vary and it includes numerous chemical elements. Examples of special glass are lenses, glass products used by the electrical and electronics industries and glass ceramics.
How is curved glass made?
Manufacturing curved glass is a time-consuming, highly specialised job. You could almost say it's a ‘pane' to produce.
Workers cut the sheet of glass to size and then clean and polish it, using a UV lamp to check for dust or impurities (any rogue particles would cause the glass to crack or shatter). They construct a steel mould shaped to the curve radius and dimensions of the desired piece. To stop the pane sticking to the mould, the glass is painted with a mixture of detergent and calcium carbonate.
Then, it is placed on the mould and loaded into the kiln. The manufacturers crank up the heat to 700°C, hot enough to loosen the bonds between the silica molecules so that the glass starts to soften and bend to the profile of the mould. Once in shape, the glass is gradually cooled over a period of about two hours.
What It Means to Temper Glass
Tempered glass, or toughened glass, has been heat-treated to make it stronger and safer to prevent injury in case if it ever breaks. In fact, tempered glass is four to five times stronger than annealed, or untreated, glass. In the event of breakage, tempered glass fractures into small, relatively harmless pieces rather than jagged shards.
Most of the glass that you see in commercial and residential spaces has been tempered. Common applications include side and rear windows in vehicles, entrance doors, shower and tub enclosures, racquetball courts, patio furniture, microwave ovens, fireplace doors and grates, and skylights. Tempered glass is also used for interior railings, display cases, office walls, and anywhere else where robust, durable glass is called for.
Steps to Temper Glass:
Glass tempering occurs following the fabrication process via the following steps.
Cut the glass into the desired shape first. Before the tempering process begins, the glass must be cut, shaped, and finish edge work. If a manufacturer attempts to etch or edge a piece of glass after the heat treatment has been done, the finished product will likely be weaker and more fragile than intended, increasing the likelihood of breakage and product failure.
Inspect the glass for imperfections. Cracks or bubbles may cause the glass to break during any part of the tempering process; if any flaws are found, the glass cannot be tempered.
Wash the glass. This step removes any tiny grains of glass deposited during grinding, as well as any dirt that could interfere with the tempering process.
Select the right tempering recipe. In order to temper glass correctly, the operator must select the right recipe based on glass type and thickness. This consists of cycle time, temperature, quenching and cooling pressure.
Quench the glass to cool it. The heated glass is subjected to seconds of high-pressure blasts of cool air, a process known as quenching. The rapid cooling causes the outer surfaces of the glass to cool and contract faster than the interior. As the inner layer of the glass cools, it tries to pull back from the outer surfaces, which causes tension. This pressure is what makes the tempered glass so strong.
Another way to temper glass is called chemical tempering. Rather than using a tempering oven, a post-production chemical compound is applied to the glass, causing the exchange of ions on the surface so the material compresses or flattens to create inner tension. But this method is not widely used because it is significantly more expensive.
Once the tempering process is complete, a trained glass inspector examines the sheet of tempered glass to ensure its quality before it is delivered to the customer.
Tempering Processes Built on Safety & Quality
More than 90 percent of the glass that Dillmeier Glass Company supplies is safety-tempered glass. As an SGCC-certified tempering company, we have perfected the process of tempering glass to meet national stringent safety requirements and quality standards, while still achieving superior turn-around times for each customer.
The benefits of laminated glass
Laminated glass is a durable and versatile glazing material providing a number of benefits. These include better protection against UV rays which can fade furnishings and carpets. Laminated glass can also help to lower noise levels, especially when it is used within double glazing. However, the main benefit of laminated glass is its safety performance.
Harder to break
Similar to glass used in car windshields, laminated glass is harder to break and offers greater security against accidental injury, attempted break-ins and severe weather conditions. The bond between the glass and interlayer combine to absorb the force of an accidental collision, resisting breakage. If the glass is broken, the shards remain stuck to the interlayer rather than breaking apart and potentially causing injury.
In the case of an attempted forced entry into your home, laminated glass will take at least two blows from a hammer to break. The interlayer will then hold the broken glass in place, requiring further blows to create a hole and gain entry into the home.
In some locations of your home, you may be required to install safety glass in order to comply with building regulations. Refer to your builder or local building authority for more information.
How to Change Stained Glass Color
Changing the color of stained glass is difficult, but possible with a bit of patience and preparation. The only way to do it and still have true stained glass is to have the piece cut out and replaced with a piece of glass in the new color. That requires a professional and can be costly. The color in stained glass is either the result of certain ingredients in the glass itself, or a special paint that gets fired onto the glass at 1100 degrees, neither of which is a practical home project. There is, however, a "cheat" for home crafters—glass paint.
Cover work area with newspaper. The pigments found in glass paint can stain most surfaces.
Lay glass bottom-up on work surface, and wipe with a damp rag to remove dust and dirt.
Clean the glass with cotton balls and alcohol to remove oils and residue. Once the glass is clean, do not touch it with your fingers to avoid re-contaminating it with oils.
Pour glass paint into the squeeze bottle and screw the cap on very tightly to prevent leaks.
Flood the glass within the lead solder outline with paint by applying gentle pressure to the squeeze bottle. Do not touch the tip of the bottle to the glass to avoid forming air bubbles. Cover the glass area with paint until you have a uniform coat no more than two millimeters thick. If excess paint gets on the lead solder, wipe immediately with a damp rag.
Allow to dry undisturbed. Apply clear topcoat using the same method if extra gloss is desired.
Mask the lead solder outline around the piece in question with painter's tape. Wipe clean with a damp rag, then clean with cotton balls dipped in alcohol. Allow to dry.
Pour glass paint onto a small plate. Mix appropriate color, if desired.
Apply a thin coat of paint to the glass with a natural-bristle brush. Keep the coat as uniform as possible, and hold the brush at an oblique angle to avoid leaving brush marks. Allow to dry.
Apply a second thin coat of paint, and allow to dry. Repeat until desired color is achieved.
Apply a clear topcoat using the same method if a higher gloss is desired.
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