Glass - Oldest known production

[Broch]

It is this part I don't quite get as quartz is pure SiO2.

I'd forgotten that!
You're right, so it's the crystal structure that must be considered an impurity? Quartz IIRC is defined as being made up of a specific crystal structure. It's even more confusing than I thought.

 

[Pattree]

I’m late to the discussion and I know nothing.

Glass as in window panes.....well it's has to be poured and it has to be poured onto something flat (the bullseye was where the last of it fell)

Does that mean that spun glass came later. Molten glass collected on a rod which was rotated, spinning out a disc that was cut into squares and diamonds when cold. In this case the lump is the point of detachment from the rod. I saw that done in a display but didn’t pay attention to the narrative.

 

[Macaroon]

Oh boy, it looks like the academics are far from specific in the definition of the two as well! An article on ancient artefacts quotes the British Museum in trying to differentiate glass and faience - I think I'm going to stop delving 'cos it's a rabbit warren - I'm going to adopt the view that faience is a glass precursor or that 'true' glass is completely fused whereas faience is not.

Sorry TeeDee, off the exact topic again!

We didn't have true, transparent, glass panes until the Middle Ages - just to bring it back

 

[Macaroon]

Off topic can often be very enlightening and broaden out a topic that some are unfamiliar with; this is a case in point. I have learned a lot from this thread and am glad of it, as always, but it wouldn't have been half as interesting without the 'meandering,' shall we say.

 

[TeeDee]

Oh boy, it looks like the academics are far from specific in the definition of the two as well! An article on ancient artefacts quotes the British Museum in trying to differentiate glass and faience - I think I'm going to stop delving 'cos it's a rabbit warren - I'm going to adopt the view that faience is a glass precursor or that 'true' glass is completely fused whereas faience is not.

Sorry TeeDee, off the exact topic again!

We didn't have true, transparent, glass panes until the Middle Ages - just to bring it back

No apologies needed - this tangent at least stays in the same ballpark of topic.

Which is a nice change.

 

[Toddy]

Sorry to disagree, we are getting into detail here, sand is mostly silica (silicon dioxide, as you say), quartz is considered an impurity, though its quantity will vary depending on the geology of the source. If faience is made from quartz I can't see how it's primary material can be sand. I suspect there is a difference between talking about material and chemistry and describing archaeological objects.

I'm an archaeologist....but my degree is from the faculty of science

Quartz is silicon dioxide, most sand is quartz, not all, but in some areas it most certainly is. Heat and compress it, and you get a fused material.
There are analogies with heating clay and it fusing into ceramics.

Doesn't mean that it's good ceramics, or glass, but it's no longer either something that crumbles to dust (sand) or something that washes into fine particles again (clay)

TeeDee asked about rudimentary glass....well that's just heated sand....quartz/ silicon dioxide, SIO2

Window glass, as in large panes has to be poured and rolled....it can as has been said, by
@Pattree, be made by spinning it out (think pizza, sort of) and again laying it down on something flat. It's a marvellous public demo that one and is oft repeated. Small panes and a lot of waste I was told....don't know, I think if you've gone to all that effort you make use of everything you can....but that's situation dependant.
Here in a land which ended up with fuel poverty, we didn't waste fuel, once we had good coal coming up, dirty though it was, it truly fueled industrialisation....but that's not the 'rudimentary glass' that TeeDee asked about....elsewhere, warmer climes, etc., once you're up to heat, it's easier to keep that than it is here and their plant growth rate means that they have more to burn.
We often forget that 20˚C is not a normal temperature for British homes in the past. Now it's common, but really we're a cool climate.

The Romans used glass for windows in Herculaneum and Pompeii as well as for important buildings in Rome itself. It was expensive, high status, but it was glass in windows, and it was pretty clear. Dates somewhere from around 100AD.

Asteroids crashing into deserts produce glass....pressure and heat again....volcanoes can produce glass if the magma is silicon rich, and it cools quickly.....but it's very, very rarely clear enough to see through. Obsidian for instance, or Arran Pitchstone.

Watching someone make glass, or faience, from literally dust and heat, is fascinating
It's one of those things that kind of defines the whole 'someone made this', for me

 

[Broch]

Yeh, apologies, I've just re-read my old notes on this. I have confused myself relying on memory (which, I must remember not to do ). Although, having said that, two of my references seem to disagree with each other - one says Silica and Quartz are related but differ in crystal structure, quartz being a form of silica. It goes on to say that Silica is a major component of sand and that quartz is an impurity. The other reference says the major component of sand is quartz! No wonder I'm confused.

Perhaps I should have asked the missus in the first place; she's a geologist