What would a glass furnace look like?

[trowelfodder]

the quartz in the welsh examples is crushed so we aren't talking big lumps and is hard to gauge exact proportions (its been a while) at a guess would say 5% quartz but dont quote me on that x.(Think am getting tired rered last post and meant huge in terms of sheer volume - the mound covered a large area but not huge in proportion) Same as you with the stone ratio tho

but of interest I dug one on Anglesey where the geology was schist same as with you and that was used in the mound

[Stuart Rathbone]

Oh, just found a pic of some of the quartz just to show the size ranges and what it looks like. No scale though, so I guess the smallest piece is about 0.5 cm

[Stuart Rathbone]

Ok, so in sequence it went like this



Removal of peat to expose collapsed fopundation



Removal of upper layers of collapse within foundation



Exposure of top layer of 'burnt material'. This layer looked a lot pinker in real life and note the top of the hearth is just becoming visible.



Removal of burnt material exposed hearth/fire box thing with its fill and surrounded by a soft brown soil



Final day shot with hearth/firebox and sandy base of building exposed. Flue/entrance partially emptied.

[Stuart Rathbone]

And as for sweat houses....this one is about 60m away but has lost its roof now. Mid 19th century.

[Dinosaur]

Pretty site! :face-approve:

My limited knowledge of glassworking is that you do need a fair amount of heat, but the whole process can be done in a very small crucible, so the heat source doesn't need to be big, just fairly intense, a small bowl furnace would be fine for knocking out beads etc, the thing you've been digging would satisfy the need for milk bottles for a small town! Annoyingly haven't currently got access to the right books so can't chuck processes, temperatures etc at you.

My personal excavation experience of glassworking is primarily post-med, bigger scale and always seems to involve bleeding knees/other bits - any of that on site? Any bits of glass waste in the soil samples, drips, those stringy bits whatever they're called etc?

[mpoole]

I can't imagine a glass furnace being enclosed in a small space like that, the constant need for a steady heat to keep the glass molten would make a small space like that almost unbearable. There's almost no evidence at all for beadmaking furnaces being of any size, in general glassworking and beadmaking don't take place on the same sites because the requirements for heat sources are not similar. I presume you're talking about a furnace to work glass rather than one to actually create glass from raw materials.

The people to talk to about glass would be the Roman glass guys, they've done more work on the subject than anyone else I know. Their furnace-building project is well-documented here, including an image of a glassblower from a Roman lamp.
http://www.romanglassmakers.co.uk/furnace1.htm

[Stuart Rathbone]

Thanks Mpoole & Dinosaur

sorry, for random reasons I met the Irish PM today (An Taoiseach) which has involved me being slightly tippsy (hint-not so slightly) so shouldn't be replying now but....

Having read the thing BAJR sent on from EH we certainly don't have any of the 'blobs' or 'threads' of glass that says we should find in our sieved soil samples so maybe I'm barking up the wrong tree. But that's why I put the question up here!

One thing that is weird about the site, as Mpoole alluded to, is the lack of space! There's barely one foot between the edge of that fire box and the edge of the wall. Now it sure does seem that that fire burnt with a fierce heat, I can't imagine anyone could have been within the building whilst that fire was lit. The funny thing about Irish sweat houses is that they burnt turf (peat) as far as I know, which in it's proper -straight out the bog form- gives off a very low level of heat allowing for a small enclosing building. This fire was burning timber (you should see the charcoal!) so would have been way too hot to stand that close to....

so....

what the hell is it?

[P Prentice]

is the pottery round your way quartz tempered?

[Stuart Rathbone]

No pottery round here at all! Seriously, two well preserved roundhouses, two of these small weird things and lots of trenches over field walls and not a single sherd of pottery to show for it! No other excavations have taken place within at least 50km so not sure about the wider area either.

Found a third glass bead today though

[trowelfodder]

This is just a random thought but if you cant be in the structure, then what about an activity like a smoke house or place to dry out food, skins etc?

Or a cooking area - I think that maybe in Cornwall (this is off top of my head as dont have any books at the mo) there seems to be a pairing of structures larger with smaller?

And this paper may be of interest when thinking about the quartz http://www.sair.org.uk/sair26/sair26.pdf