Types of Glass

Sealing Glass

A wide variety of glass compositions are used to seal metals for electrical and electronic components. Here the available glasses may be grouped according to their thermal expansion which must be matched with the thermal expansions of the respective metals so that sealing is possible without excessive strain being induced by differing levels of expansion.

For sealing to tungsten, in making incandescent and discharge lamps, borosilicate alkaline earths-aluminous silicate glasses are suitable.

Sodium borosilicate glasses may be used for sealing to molybdenum and the iron-nickel-cobalt (Fernico) alloys are frequently employed as a substitute, the amount of sodium oxide permissible depending on the degree of electrical resistance required.

With glasses designed to seal to Kovar alloy, relatively high contents of boric oxide (approximately 20%) are needed to keep the transformation temperature low and usually the preferred alkali is potassium oxide so as to ensure high electrical insulation.

Where the requirement for electrical insulation is paramount, as in many types of vacuum tube and for the encapsulation of diodes, a variety of lead glasses (typical containing between 30% and 60% lead oxide) can be used.

  • British Glass represents the interests of primary glass manufacturers and the glass supply-chain, from raw materials to retail and the end-consumer" credits="n/a" >
  • Modern life would not be possible without glass
    But, what is this amazing substance, where does it come from and how is it made?" credits="n/a" >
  • Find a reputable supplier from our member directory" credits="n/a" >
  • Learn about the different methods of manufacturing glass in our information section" credits="n/a" >
  • Did you know that Glass is 100% recyclable and can be recycled an infinite number of times without loss of quality, strength or functionality?" credits="n/a" >
  • We provide relevant, impartial, and comprehensive advice and information - from leading experts across key legislative areas" credits="n/a" >
  • British Glass represents the interests of primary glass manufacturers and the glass supply-chain, from raw materials to retail and the end-consumer" credits="n/a" >
  • Learn about the amazing material glass" credits="n/a" >
  • British Glass represents the interests of primary glass manufacturers and the glass supply-chain, from raw materials to retail and the end-consumer" credits="n/a" >
  • Our enviromental section goes into more depth on the environmental and energy issues affecting the glass supply chain" credits="n/a" >

In this Section


About Glass



 
 

Because of the differences in the various methods of manufacture, the industry is divided into 5 main sections under the general headings: Container glass; flat glass; scientific/technical glass; domestic glass; and fibre glass.


British Glass - Twitter

We hosted a forum for glass industry HR leads, focussing on the forthcoming Apprenticeship Levy. Read the article: https://t.co/SU3bfvbeLG

RT @BeatsonClark Thanks to @FoodManufacture for featuring us in their article about glass bottles for craft beers and spirits https://t.co…

Our HR forum w/ @RNNGroup revealed #apprenticeshiplevy offers employers more value than many companies realise. https://t.co/PWJDvCKsxL

RT @SaintGobainUK Ten valuable news resources for construction professionals, from @Isover https://t.co/7xLqY2s8Zd https://t.co/FtLHs13S0a