Mid 18th Century glass

[Mark P]

Hello everyone;

 

I thought that my fellow modellers might be interested in the following document,  which I found at the National Archive in England,  whilst searching for a somewhat different subject.

 

This lists the prices,  sizes and quantities of a delivery of glass made to Deptford Dockyard in November 1750.

 

The biggest pieces are quite large:  31" x 21 1/2",  3no.  Their rarity and value is reflected in their price,  £7.0.0 each,  which is many times higher than the smaller,  more numerous pieces.

 

Lower down in the list are some pieces of mirrored (silvered) glass,  some of which are again quite large and expensive.

 

Clicking on the image should make it larger.  If not,  right-clicking on the image should bring up a menu with an option to 'open image in new window' option which makes it larger and easier to read.

 

All the best,

 

Mark P

Edited June 27, 2016 by Mark P

[mtaylor]

I like the line at the bottom.. "We are humbly of the opinion the prices he asks are reasonable".  Big pieces would have priced higher given the state of the art of glass making back then.  

 

Thanks for posting this.

[druxey]

This is in accord with what I've read elsewhere. Large 'blown plate' aka 'ground glass' was made by grinding and polishing 'broadsheet glass'. This accounts for its expense. Large pieces were principally used in coaches and for mirrors.

 

Nice find, Mark!

[wefalck]

Wasn't this blown into a long cylinder, the bottom and top disc (with the blow-pipe attachment) cut off, the cylinder split lengthwise and then rolled flat while still hot ? Cheaper and smaller panes were cut from the discs, which accounts for the streaks often seen in old window panes.

[Mirabell61]

Wasn't this blown into a long cylinder, the bottom and top disc (with the blow-pipe attachment) cut off, the cylinder split lengthwise and then rolled flat while still hot ? Cheaper and smaller panes were cut from the discs, which accounts for the streaks often seen in old window panes.

 

Wefalck,

 

that sounds like an interesting technique for for making early "flat glas"   , thanks for sharing...

 

Nils

[druxey]

Yes, that's my understanding, Welfalk. 'Blown plate' is another name for 'cylinder glass'. There was also spun glass, which was disc-like, the pontil mark piece of the disc becoming the cheapest 'bulls-eye' seen in old panes.

Edited June 28, 2016 by druxey

[wefalck]

Indeed, the bull's eye-glass (or 'Butzen' in German) has been very common and is used in 'romantic' reconstructions of medieval windows. However, considering that there only two bull's eyes coming out of each cylinder and only one from each disc, there must have been a considerable production of plate glass to give sufficient numbers of them for a window. I guess, from the mid-19th century on, they were not only 'waste' products anymore, but made specifically to meet medieval-revival demands. Also, in Germany the 'Butzen' often are 'bottle-green', indicating that inferior quality raw materials with a lot of metal contaminants were used - so the associated flat glass must have also been green.

 

Here is an image from Wikipedia that shows the production of disc-glass in the 'forest' ('en bois', because they needed the wood for fuel):

If I am not mistaken, sometime in the last quarter of the 19th century the float-glass was inventend in France, whereby the the near-liquid glass was poured onto a bassin with mercury. Indeed, France seems to have been technologically ahead in glass production for quite some time.

[rwiederrich]

I've seen windows in very old monasteries in Germany that had this type of spun glass in the pains. The cut off or nib(butzen) was placed in a lower or upper corner to provide the larges unobstructed view.  I have even seen windows with the defect right in the middle adding to the decoration.

 

Fascinating.

 

Rob

Edited July 22, 2016 by rwiederrich

[wefalck]

Following the Medieval Revival fashion in Europe from around the 1840s these 'Butzenscheiben', as they are called in German, have been used in 'restoration' and imitation projects. They have become associated with a 'romantic' view of small German towns and the likes, but can be seen in France, the UK, and other places as well.

[Doreltomin]

Fascinating subject!

 

Thank you Mark for starting it and everybody else for their valuable information added to the thread!