- How is commercial glass made and what is it made of?
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Glass is made by mixing different minerals like silica sand, Soda ash (sodium carbonate),
Limestone (CaCO3) and some oxydizing materials. Each one of them
add different characteristics and elemental features in glass production.
70%-74% Silica sand(SiO2): Is pulverized sand we normally see at sea or deserts, it gives glass its crystaling properties or amorphous molecular structure.
12%-16% Sodium Carbonate(Na2CO3): Is a mineral used to lower the melting point of silica from 1,700 to 830 Celsius degrees.
6%-14% Calcium and magnesium oxide: These minerals serve the purpose of stabilizing glass inhibiting its solubility in water by making it pure.
1%-3% Other oxides: Give glass specific properties, like shininess, refraction level, color, thermal and electrical resistance among other. - Is it true that glass is a liquid?, and that proof of it, is in glass windows made centuries ago, where the glass is seen to be thicker at its base?
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There is a myth saying that glass is a constantly flowing liquid.
This myth comes from looking at glass from medieval churches
where it was clearly visible that those pieces of glass were thicker at its base.
What breaks this myth is the knowledge about glass manufacturing processes from those times. Back then, glass was made using a process called crown or blowing. These processes created pieces of glass with variable thickness, and when installed they were placed with the thickest side down. In 1959 a technological innovation came out on glass manufacturing process, it is the same being used now a days. The process is called "Floated", and it is capable of creating pieces of glass with uniform thickness, which doesn't change through time. - Is glass a solid or a liquid?
- There is no exact answer to this question. In terms of molecular dynamics and thermodynamics it is possible to justify glass as a liquid with a very high level of viscosity, or as an amorphous solid, or as neither solid or liquid. Difference is truly about semantics. However, if we are pressed to make a logic decision based on our own daily experience, (accounting for physical, tangible properties) we can call glass a solid.
- What is Safety Glass and where should it be used?
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Safety Glass is a glass which breaks in a non life threatening way,
and it helps reduce injuries in case of an accident.
It should be used in areas where human casualties could happen due to glass breakage.
There are two kinds of safety glass:- Laminated
- Tempered
- What is tempered glass and what are its advantages?
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It is a glass with a surface compression of 1,000psi or higher on its outbound and
9,700psi on its inbound.
Features
- 4 to 5 times more resistance to impacts and sudden temperature changes, compared to regular non-tempered glass
- An uniform breakage pattern of small non life threatening pieces called "cullets". In an area of 2.5" by 2.5" there should be at least 60 fragments (cullets) and a maximum of 500 fragments. Each individual fragment must have a weight less than 4.2 grams for glass 3 - 6mm of thickness
- Which are the most common uses of tempered glass?
- It is used on applications where there is a risk by glass breakage, like: vehicles, buildings, appliances, etc.
- How do I know if a glass is tempered or not?
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The easiest and most practical way to know if a glass has been
tempered, is by looking for a logo printed with ceramic paint,
that makes reference to this process.
If the glass does not have the said logo, you could know by knocking on it. Frameless tempered glass sound is dry, and it vibrates less due to the compression on its surface which acts as a "protective shield". The problem with this method is that you'll need a non tempered glass with the same thickness and size to compare it to, and you won't be able to know if it is well tempered.
Another way to know is by doing a photoelastic test which will determine the tension all over the glass surface.
The most reliable way of knowing if a glass is tempered, is by breaking it and looking at the fragmentation pattern created by its pieces. - What's the difference between fully tempered glass and heat strengthened glass?
- Both glasses are heated up evenly to an approximate temperature of 680 degrees Celsius. But the main difference comes at the end of the process, when cooling down the pieces. The cooling pressure applied is different, producing different surface and edge compression (Edge compression: 9700-10,000 psi for tempered glass and 3,500-5,500 on a heat strengthened glass), thus, creating changes to their fragmentation pattern and their levels of mechanical and thermal resistance.
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