Glass as a Material for Window Work

Basic materials, Products, Generic Descriptions.
johnleeke
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Glass as a Material for Window Work

Postby johnleeke » November 18th, 2011, 4:43 pm

Title: Glass as a Material for Window Work

(We need a good, factual, and brief (100 to 200 words total) write up on glass as a material. Following are some notes & ideas. When you see "..." that is an invitation to add more yourself. Click on "Post Reply" above to comment.)

Notes & Discussion:

types of old glass based on method of manufacture, how to recognize each (we will use Amy's write up on types, see below…)

types of new glass in common use today: float glass, reproduction glass...

old existing or salvaged glass vs. new reproduction glass...

...

(this write up does not need to cover what to do with glass, that is covered in all the individual treatment standards)

oculus
Posts: 66
Joined: May 18th, 2011, 12:15 am

Re: Glass as a Material for Window Work

Postby oculus » December 28th, 2012, 11:14 pm

So John here is my abbreviated (I know it doesn't look it) version of the types of glass. I tried to whittle it down but it is a complex subject. Let me know if you need it shorter.


Crown Glass-The earliest form of window glass that is found in America. Formed by gathering molten glass onto the blowpipe, an air bubble is formed, and then through careful manipulation of the bubble, a large round balloon is formed. At this point the blowpipe is cut off and a punty is attached. The hole created by the absent blowpipe is widened. As the hole becomes larger the punty is twirled so that a large disc of viscous glass is formed. At the height of production discs reached 52” in diameter. Once the disc is annealed it is cut into useful pieces. The remaining center roundel or bullion was primarily used for utility purposes.
Qualities to look for:
-Some curved ripples can be seen in the final product
-Use of the roundel as a pane.
-Bubbles in the glass follow the curvature of the stretch. Ellipses arranged in arcs.

Cylinder Glass (hand-blown and machine drawn)- As larger pieces of glass were desired the technology for making window glass developed to meet the demand.

Hand-Blown: In the hand-blown process the molten glass was gathered on the blowpipe similar to the manufacture of crown glass. More molten glass had to be taken up on the end of the pipe since the amount of material gathered determined how long you would be able to make the cylinder. Great strength by the workmen was essential. A large air bubble was formed and the molten glass worked into a pear shape. To get the wall thickness to remain consistent the worker had to carefully stretch the shape vertically. At times the molten glass bubble was swung up over the head and down into deep pits which allowed for cylinders of great length to be produced. By the 1860s cylinders of 50” in length by 36” wide were produced. After the cylinder was created it was removed from the blowpipe and was slit down the length of it. Afterward it was placed into a flattening kiln where it would slump down flat, then placed into an annealing oven. The flattened sheets were then cut into the desired sizes.
Machine Drawn: In the early 1900s John Lubbers developed a process for drawing tall cylinders of glass using machinery. Known as the Lubbers process. This revolutionary process allowed for cylinders up to 45’ in length to be produced. The slitting and annealing process was similar to that used for the hand-blown glass.
Qualities to look for:
-Small pits or inclusions on the surface of the finished glass.
-Bubbles in the glass follow the longitudinal stretch of the cylinder.

Float Glass: Also know as the Pilkington Process after the inventor of the technique Sir Alastair Pilkington. He developed this manufacturing process in the 1950s. Molten glass is poured onto a bed of molten tin. Like oil in water the glass floats upon this bed. No bubbles or distortions are present in the glass sheet. Thickness is controlled by the speed with which the molten ribbon is removed from the tin bath.
Qualities to look for:
-Distortion free view from all angles. No bubbles or blemishes are present.
-Clear glass of uniform thickness.

Resources:
Tutton, Michael and Elizabeth Hirst, eds. Windows: History, Repair and Conservation, Great Britain: Donshead, 2007.
Munro, William L. Window Glass in the Making, Pittsburgh: n.p., 1926.
Pender, Robyn and Sophie Godfraind, vol.eds. Practical Building Conservation: Glass and Glazing, Great Britain: Ashgate Publishing, 2011.
Amy Harrington McAuley
Oculus Fine Carpentry, Inc.
http://oculuswindow.blogspot.com/
oculuswindow@gmail.com

"Opportunity is missed by most people because it is dressed in overalls and looks like work"-T.Edison

johnleeke
Posts: 375
Joined: April 13th, 2011, 7:34 pm
Full Name: John Leeke
Location: Portland
Organization: Historic HomeWorks
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Location: Portland, Maine
Contact:

Re: Glass as a Material for Window Work

Postby johnleeke » December 29th, 2012, 10:36 am

Amy, this is excellent. Thank you, thank you, thank you.
John
Standards Co-Founder
Standards Editor

http://www.HistoricHomeWorks.com


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