Categorization of Glass and its Application: Silicate Glass Part 2


3. Lead glass: When soda lime glass or potassium lime glass is added with oxidized lead, it becomes lead glass. This material has a high specific gravity, high refractive index and dispersive power while having a low softening temperature, making the manufacture process much easier. The refractive index can be further enlarged by applying cut crafting. These are used not only for high-end kitchenware, but also in achromatic optical lens, lamp glasses for electron tubes, and shield glasses for x-rays and gamma rays.

Lead glass is also called flint glass, originating from how flints were used initially for the base material of silicate. Another type of lead glass with a different build is called crown glass, because the fabrication of glass plates in the old days required blowing of the plate into a crown shape and then widening it.

4. Barium glass: This type of glass is typically used for optical purposes. The main component of barium glass is barium oxide. It is used to calibrate the aberration of the lens, and was created first by F.O.Short during the late 19thcentury in Germany. There are two major types of barium glass: low dispersion – high refraction barium crown glass and high dispersion – high refraction barium flint glass.

5. Silicate Glass: This is also often referred to as quartz glass or smelted crystal glass. It consists of 99.5% SiO2. Thermo-expansion rate is at a very low degree (around 0.5 x 10-6linear), and has a very good heat resistance. Normally when one says ‘shrunk glass’ (or heat-resistant glass), he/she is referring to 96~99.3% silicate content (Product name Vycor). With high heat resistance and excellent acid resistance, also permeable by UV rays, these glasses are used for glassware in physicochemical fields, prisms for UV spectrums and more. However, due to its requirement of 2,000°C or higher when smelting, quartz glass and shrunk glass require special techniques for production.

Categorization of Glass and its Application: Silicate Glass Part 1


This is the most common type of glass that has natural silica as the main structure of the network. There are many different kinds of silicate glass including sodium lime glass, potassium lime glass, lead glass, barium glass (i.e. network-modifying oxide glasses) and also pure silica glass (quartz glass).

1) Sodium lime glass: This glass contains sodium as the network-modifying ion. The molecular composition is expressed as Na2OCaO·5∼6SiO2. This is the most common type of glass used commercially, and can be found in everyday items such as glass boards, bottles, mirrors and kitchen glassware. The main constituents include silica, sodium carbonate (soda ash), and quicklime. Toxic impurities are mainly iron. When smelting the batch, there are occasions where impurities enter the network, causing the glass to have a blue-green color instead of clear. To counter this, traces of chemicals causing red resulting color such as manganese, selenium and nickel are often added to the batch.

Alternatively, one can add a charge to the oxidized steel from 1 to 2, making the resulting glass to display a very light yellow color that is less visible. To do this, oxidizers like sodium nitrate can be used as a chemical decolorant. Since sodium lime glass contains more sodium compared to other types of glass, it has a large expandability when exposed to heat (Linear expansion rate of approx. 10 x 10-6), and therefore isn’t very thermostable. Also, the sodium on the surface of the glass might leach when it comes to contact with water as the sodium and the hydrogen ions go through ion exchange, giving the material a low water-proof quality.

2) Potassium lime glass: This is identical to soda lime glass if you replace parts of the sodium content with potassium. Potassium lime glass is more rigid than soda lime glass, and also has a higher water resistance. It has been widely used has hard glassware for physico-chemical apparatus. Commercially, it is used in imitation jewelry, parent glass for photographic filters, optical glass, and eyeglasses. Those with an exceptionally high transparency are used for high quality kitchenware, and are referred to as crown glass.

Categorization of Glass and its Application: Introduction


Glass can be categorized by different sets of criteria such as build, shape or application, so it is difficult to have a set categorization that works for all situations. Categorizing glass by build, oxide derivative glass can be divided into silicate glass, borosilicate glass, phosphate glass and etc. based on the main content of the network structure. In reality, most glass used commercially and industrially are silicate glass. Because of this, silicate glass is further categorized into quartz glass, sodium glass, sodium lime glass, lead alkali glass, sodium lime alumina glass and more.

Contents and Structure of Glass


The exact contents of glass vary by type. However, excluding special glass such as quartz glass, most glass material consists of network forming matter that acts as a principal agent of the glass structure. These structures are supported by a secondary material that loosely binds to the structure chemically, and decides factors such as solubility, tint, opacity, chemical durability and conductivity of the glass.

The main part of the glass is referred to as the network-forming oxide and acid oxides such as silica, anhydrous boric acid, and phosphoric anhydride are used conventionally. The secondary constituents are called network-modifying oxides. Examples for this include alkaline metals such as sodium, potassium, calcium, barium, oxides of alkaline earth metals, and oxides of lead or aluminium.

On a microscopic scale, the hydrogen ions and the cations of the network-forming oxide form a strong bond, creating a sort of a network. The empty parts within this network are then occupied by metal ions formed through modifying oxides. This causes a disturbance in the overall structure of the network.

The inserted ions (Network-modifying ions) are in the size range of 0.5 ~ 2.20 Å. Ions with a small diameter or those with a high valence often have difficulties moving from the empty slots of the network, and this causes a noticeable effect on the macroscopic properties of the glass.

Furthermore, ions with higher valence and smaller diameters have stronger bond energies. Using these specific ions as network-modifying ions, it is easy to form glass. As an example, sodium and potassium ions have the same valence of +1, however since sodium ions are smaller in diameter, sodium lime glass is easier to fabricate compared to potassium lime glass. This is also why sodium lime class (soda lime glass) is used more conventionally.

iloome Introduces the World’s First Tempered Glass Screen Protector That Provides Full Screen Protection and Coverage for the iPhone 6 and iPhone 6 Plus

SAN DIEGO, CA–(Marketwired – Sep 22, 2014) – iloome, a leading supplier of tempered glass screen protectors for mobile devices sold under the ScreenMate® brand name, today announced the availability of its ScreenMate® for the iPhone 6 and iPhone 6 Plus. The Company believes that this is the world’s first tempered glass screen protector that fully covers and protects the screens of iPhone 6 and iPhone 6 Plus. Due to the curved edges of the iPhone 6 and iPhone 6 Plus, there are currently no tempered glass screen protectors available in the market that cover the entire screen surfaces of these devices other than the ScreenMate®. The tempered glass screen protectors currently being sold do not fit the contours of the iPhone 6 and iPhone 6 Plus and are therefore too small, leaving about a four millimeter gap around the outside of the screens. Through its innovative design, the ScreenMate fits perfectly over the screens of the iPhone 6 and iPhone 6 Plus, including the contoured edges, and provides unparalleled screen protection for these devices that were recently released in the market.

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What is Glass?


[Editor’s note: Informative Rocket Scientist is back after nearly 2 years! iloome Blog will be regularly updated again so please check back for interesting and technical facts about glass products!]

Glass, to simply put, is a highly transparent object resulting from dissolving materials such as sodium, calcium and silicate at a high temperature and subsequent cooling. Conventionally, glass was primarily composed of silicate, but newer technology in glass manufacturing has allowed us to create phosphate- and borate- based glass as well.

Usually, the shape of a piece of glass is fully determined when the molten liquid starts to solidify through cooling, but depending on the raw material of the glass, the crystallization may be delayed significantly even at cooler temperature while its viscosity decreases as it eventually hardens. We call that in the free state as prior to the solidification as previously described as “amorphous solids,” while the inorganic material after the solidification as “glass.” There are several types of chemical compounds can that be used to create glass, including selenium-based sulfur and silicon, and germanium-based oxide and boron oxide sulfide salts.

The chemical reaction to create a piece of glass occurs through heating of a predetermined ratio of metal or oxide of the base metal, and while the substance may appear solid, but it does not have the crystal structure that supports its shape until solidification is totally complete and generally does not have a constant melting point throughout the piece of glass. Due to these reasons mentioned previously and the high-viscosity nature of the glass, material engineers generally consider glass as an amorphous material, similar to asphalt.