Topic: What is glass? Is silica a required component of glass?

[flying free]

As a consequence of David posting a thread here
http://www.glassmessages.com/index.php/topic,52882.msg300315.html#msg300315
where in discussion Anne raised the subject of the Archive section on the board, I went to the archive to have a look at the topics.

One of them was a topic started by Leni titled: 'Just what do we mean by 'Glass' '
http://www.glassmessages.com/index.php/topic,24901.msg138402.html#msg138402

Coincidentally, I'd come across an old glass book for sale, possibly a rare book, but whatever the reason, it was extortionately expensive.  So I went to look it up to see why it would cost so much.

In so doing I happened upon another book copyrighted in 2005,
 Introduction to Glass Science and Technology
 by J. E Shelby
http://books.google.co.uk/books?id=ZeF_QLW6-xsC&pg=PA99&dq=textbook+of+glass+technology&hl=en&sa=X&ei=j2WqUefzC6Sx0QXt6YCADQ&ved=0CF8Q6AEwCA#v=onepage&q=textbook%20of%20glass%20technology&f=false

I looked it up and some text was available on Google books.
To my amazement, in the first few pages  under the heading of 'Definition of Glass' on page 3 it states
a) that silica is not a required component of a glass and
b) that melting is not a requirement for glass formation.

the book is copyrighted 2005 The Royal Society of Chemistry. 
I've not read the whole thing (and I know I'm not going to lol) but even the first few pages make very interesting reading if you're interested in the detail in this way.
m
 

[Lustrousstone]

Your questions are wrong. They should be What is "a" glass? and Is silica a required component in all glass?

This kind of peripheral to what we are interested in here in that it's physical chemistry. Glass in it's ultimate definition is just a particular solid state (complete lack of crystallinity) combined with a particular behaviour (glass transformation). The book starts with the physical chemistry of all glass before going on to glass as we are interested in it.  No melting isn't essential but phase transformation can be, i.e., solid to liquid to solid or solid to vapour to solid. Alternatively, we get rid of the crystallinity completely by irradiation

[flying free]

Thanks for the explanation
 I didn't ask any questions though
I just happened upon that book, having coincidentally come across Leni's thread just beforehand and thought it might make interesting reading.  The two comments at the beginning struck me as interesting because I've no knowledge of this kind of thing 
m

[Lustrousstone]

You did in your title 

[flying free]

oh yes  I'm an idiot 
I realised what you meant afterwards as well - it's an interesting book though isn't it?  I'm half tempted to have a go at trying to understand it.  I'm just off to quiz eldest on AS level Chemistry revision, so maybe after that
 m