Glass - What Is It?

Monday, 2 January 2006  |  Admin
GLASS - WHAT IS IT?

Well it’s a material that we all use daily, even if only to look through on to the outside world, though most of us do not understand it.

For many years glass has been believed to be a supercooled liquid. This was because, in medieval cathedrals the glass panes were observed to be thicker at the bottom than they are at the top creating and perpetuating the myth that glass behaves as a liquid.

We now know however, that glass is neither a liquid nor solid. It is technically classed as either an amorphous solid or a highly viscous liquid depending on who you ask. It is a state of matter somewhere between the a liquid and a solid that is so unique we struggle, even now, to find an accurate term to describe it. Meaning that at any given time some glass molecules are behaving as a liquid while those right next to them as a solid.

It is a material that occurs naturally, around volcanic activity as it is created by the vitrification of silica, the foundation of all rocks. Therefore glass appears all over the universe, wherever there is heat and rocks glass can occur.

Man has used glass since the very beginning of our existence, knapping it  into arrow heads and small blades, in the same fashion as with flint and other stone tools. (The amazing discovery of stone tools over 3 million years old recently has changed our view upon when tools were first used and by what species of hominin. ). An interesting story told about when Captain Cook first landed on Australia, the Aboriginal locals saw glass for the first time and as they were living a new stone age existence, proceeded to take broken bottles and knapped them into arrow heads.

Photo from http://sticksnstones89.deviantart.com/art/Cobalt-Blue-Glass-Arrowhead-389258297
 

Eventually man discovered how to make glass for themselves, no one knows how it was discovered and there are several theories for this discovery. I have my pet theory, one I came up with myself and I believe that it is more than likely to be the truth, here it is.

Ceramics have been made for millennia, the early pots were not fired in kilns but within pyres, I have done this at a living history event at St Donats Castle south Wales many years ago. It was apparently the females of the tribes that made the pots and the men (being men) fired them, all men love playing with fire, admit it.

 

So imagine one day the pots were all dry and ready for the firing the men built the Pyre around them and it was set on fire, the temperature was judged by the colour and to make it hot air was fanned on the fire and to slow or cool it ash was shovelled onto it. Now we men have certain traits, one of which is that we can be easily distracted, therefore imagine this scenario. The pyre is burning and a stiff breeze is blowing, fanning the flames, when something happened that distracted the men firing the pots and the fire was allowed to get too hot, so instead of semi-vitrifying the ceramics they were vitrified completely, so instead of these useful pots all the remain when the Pyre cooled was amorphous mass of glass. The women of the tribe would have been very fed up with their males and there would have been an ear-bashing session for them.  To placate their spouses I can imagine the men taking the glass blobs and carving them into Amulets as gifts – 'Look sweetheart what I have made you'. And thus man made glass was discovered. For the first few thousand years of glass manufacturing, all that was made was carved blobs as statuettes and jewellery.

 

This as stated previously is purely my theory, but I am a great believer in the fortuitous cock up theory, over genius design any day.

 

 

Jim Adlington