Window Glass.
Post new topic   Reply to topic
Historic HomeWorks Forum Forum Index -> Windows & Doors Goto page 1, 2, 3  Next 
View previous topic :: View next topic  
Author Message
johnleeke
Site Admin


Joined: 20 Aug 2004
Posts: 2940
Location: Portland, Maine, USA

PostPosted: Wed May 05, 2010 1:14 pm    Post subject: Window Glass. Reply with quote

(update: 4/21/12, new: bent glass source)

Types of Window Glass

Crown Glass was common in the 18th and early 19th centuries. It was hand-made by blowing molten glass into a hollow sphere, cutting the end of the sphere open and then spinning the sphere into a thin flat disk that was laid on a table, cooled until solid, then cut into window panes. Crown glass has striking optical distortions of curvy waves called "rheams," tiny bubbles called "seeds" and even larger bubbles and other character-defining "defects."
Click for image:

http://babel.hathitrust.org/cgi/imgsrv/image?id=uc2.ark%3A%2F13960%2Ft3vt1ht7c;orient=0;size=100;u=1;seq=182;num=178

Popular technology; or, Professions and trades.
By Edward Hazen. Vol. 2, p. 178.
"12. Blowing. The operation of blowing is nearly
or quite the same in the production of every species
of glass ware, in which it is employed. The manipu-
lations, however, connected with making different ar-
ticles, are considerably varied, to suit their particular
conformation. This circumstance renders it impos-
sible for us to give more than a general outline of the
process of this manufacture.

13. In the formation of window glass, the work-
man gathers upon the end of an iron tube a sufficient
amount of the metal, which he brings to a cylindrical
form by rolling it upon a cast iron or stone table.
He then blows through the tube with considerable
force, and thus expands the' glass to the form of an in-
flated bladder. The inflation is assisted by the heat,
which causes the air and moisture of the breath to ex-
pand with great power.

14. Whenever the glass has become too stiff, by
cooling, for inflation, it is again softened by holding it
in the blaze of the fuel, and the blowing is repeated, un-
til the globe has been expanded to the requisite thin-
ness. Another workman next receives it at the oth-
er end, upon an iron rod, called a punt, or punting iron,
when the blowing iron is detached. It is now open
ed, and spread into a smooth sheet, by the centrifuga.
force acquired by the rapid whirl given to it, in the
manner exhibited in the preceding cut. The sheet thus
produced is of a uniform thickness, except at the
centre, where the iron rod had been attached.

15. An inferior kind of window glass, the materi-
als of which are sand, kelp, and soap-boilers' waste,
is made by blowing the metal into cones, about a foot
in diameter at their base ; and these, while hot, are
touched on one side with a cold iron dipped in water.
This produces a crack, which runs through the whole
length of the cone. The glass then expands into a
sheet somewhat resembling a fan. This is supposed
to be the oldest method of manufacturing window or
plate glass.

16. The window glass produced in the manner first
described, is called crown glass ; and the other, broad
glass. But by neither of these methods can the lar-
gest panes be produced. The blowing for these differs
from the methods just described, in that the material
is blown into an irregular cylinder, open at its further
end. When a sufficient number of these cylinders have
accumulated, the end to which the blowing iron had
been attached, is capped offby drawing round it a circle
of melted glass, and the cylinder is divided longitudi-
nally by touching it through its whole length with a
hot iron. The cylinders, in this state, are put into
the annealing oven, where, by aid of a heat which
raises the glass to redness, it is expanded into sheets.
These sheets are then broken into panes of several
sizes by the aid of a diamond and a straight edge, as in
the case of glass blown by other methods. "

http://tinyurl.com/2vujlmq

Cylinder Glass was common throughout the 19th century up until the 1950s. The view through this glass is optically distorted in parallel waves that are sometimes straight or slightly curved. This glass was first made by hand-blowing a hollow sphere of glass, which was then extending into a cylinder 18 inches in diameter and up to 9 feet long. The ends were cut off the cylinder, which was slit along the side then flattened out and cut into panes. By the 20th century machinery produced the cylinders up to 30 inches in diameter and 40 feet long.

20th century cylinder glass production:
http://www.stainedglassltd.com/newsite/oldwindowglass.php

Drawn Sheet Glass
Drawn Sheet glass was made by dipping a leader into a vat of molten glass then pulling that leader straight up while a film of glass hardened just out of the vat - this is known as the Fourcault process, developed in the early 20th century. This film or ribbon was pulled up continuously held by tractors on both edges while it cooled. After 12 meters or so it was cut off the vertical ribbon and tipped down to be further cut. This glass is clear but has thickness variations due to small temperature changes just out of the vat as it was hardening. These variations cause lines of slight distortions. This glass may still be seen in older houses.
Source: Wikipedia http://en.wikipedia.org/wiki/Fourcault_process


Float Glass was introduced in 1959 and is the common window glass of today. This glass is optically regular and distorts the view through it very little. It is manufactured by the drawn method where a ribbon of molten glass is draw out horizonally and floats over a bath of molten tin and then runs off onto rollers as it cools and solidifies.

Single-strength Glass (or SSB stands for Single Strength Billet) about 3/32" thick.

Double-strength glass (or DSB stands for Double Strength Billet) this glass is about 1/8" thick.

Reproduction Glass
Two or three companies make window glass products with optical distortions that imitate authentic glass. Once you get to know what authentic glass looks like, it is clear that the reproduction glass does not really look like the authentic glass. It is made with very different methods that cannot accurately recreate the old look.

The differences between the optical distortion of authentic glass and reproduction glass may seem subtle to the inexperienced eye, until you have seen them side by side. The way to learn the difference is to get a few samples of the reproduction glass and compare them to the glass in old windows. After you have done this 50 or 100 times you will know the difference.

It can be interesting to collect samples of the different kinds of glass you are working with. As your collection develops you will learn to instantly recognize the different types: crown, cylinder, float. And, you will also be able to recognize the reproduction glass for what it is--a distant imitation.

Suppliers of Authentic Old Glass:

Kennett Glass Company
Bob Davis
110 West State Street
Kennett Square, PA 19348
610-444-4181
Kennettglass@verizon.net
www.kennettglass.com
Authentic old glass, from Pennsylvania, sorted into 25 year periods from the 1700 to 1925, will ship anywhere


Fairview Restorations
5607 Old National Pike
Frederick, MD. 21702
240 529-8199
fairviewgl@aol.com
www.fairviewglass.com
Authentic old glass from the Baltimore and Washington metropolitan area houses that lie in the path of urban sprawl and are slated for demolition

Please tell us if you know of a supplier of old window glass.

Bent Glass:

Bent Glass Discussion:
http://historichomeworks.com/forum/viewtopic.php?p=3229#3229

Bent Glass Supplier:

Curran Glass Studio
John Curran
6507 Ogden Avenue Berwyn, IL 60402
708-795-8620
www.curranglass.com
bent glass in sizes up to 46" x 46" and 29" x 56", hand & machine beveling


Cutting Glass

Discussion on glass cutters:
http://historichomeworks.com/forum/viewtopic.php?p=10669

Repairing Cracked Glass

Discussion on taping cracked glass as temporary stabilization method:
http://historichomeworks.com/forum/viewtopic.php?p=10707

Discussion on adhesive methods:
http://historichomeworks.com/forum/viewtopic.php?t=1321

Discussion on foil/solder and lead came methods:
http://historichomeworks.com/forum/viewtopic.php?t=2289


Last edited by johnleeke on Wed Jan 29, 2014 4:36 pm; edited 26 times in total
Back to top
View user's profile Send private message Send e-mail Visit poster's website
Mike-in-Maine



Joined: 08 Nov 2008
Posts: 145
Location: Fort Kent, ME

PostPosted: Thu May 06, 2010 11:06 am    Post subject: Reply with quote

Excellent review of the most basic of basics of glass. Good reference.

Now how can one tell "period" wavy glass from newer wavy glass. The genuine 100+ year old stuff vs newer glass that might exhhibit similar characteristics?

And how was the "wavy" glass made, compared to the new non-wavy glass. It is a different process, from what I recall.
Back to top
View user's profile Send private message
rncx



Joined: 21 Jun 2008
Posts: 660
Location: Little Rock, AR

PostPosted: Thu May 06, 2010 12:43 pm    Post subject: Reply with quote

http://en.wikipedia.org/wiki/Glassblowing
Back to top
View user's profile Send private message
TimB



Joined: 03 Sep 2009
Posts: 43

PostPosted: Thu May 06, 2010 12:48 pm    Post subject: Window Glass Reply with quote

For an excellent overview of changing window glass technologies, see:
Garvin, James L., [/u]A Building History of Northern New England.

Here's a preview on google books:
http://books.google.com/books?id=oC4zG5aR4rwC&dq=a+building+history+of+northern+new+england&printsec=frontcover&source=bn&hl=en&ei=ePziS7yQJIOclgeTvZTEAg&sa=X&oi=book_result&ct=result&resnum=5&ved=0CDAQ6AEwBA#v=onepage&q&f=false

_________________
Tim Brosnihan
Back to top
View user's profile Send private message
Mike-in-Maine



Joined: 08 Nov 2008
Posts: 145
Location: Fort Kent, ME

PostPosted: Thu May 06, 2010 1:08 pm    Post subject: Reply with quote

Oooooo.... nice book!
Back to top
View user's profile Send private message
johnleeke
Site Admin


Joined: 20 Aug 2004
Posts: 2940
Location: Portland, Maine, USA

PostPosted: Thu May 06, 2010 1:33 pm    Post subject: Reply with quote

Quote:
Now how can one tell "period" wavy glass from newer wavy glass. The genuine 100+ year old stuff vs newer glass that might exhibit similar characteristics?


Reproduction Glass
Two or three companies make window glass products with optical distortions that imitate authentic glass. Once you get to know what authentic glass looks like, it is clear that the reproduction glass does not really look like the authentic glass. It is made with very different methods that cannot accurately recreate the authentic old look.

The differences between the optical distortion between authentic glass and reproduction glass may seem subtle to the inexperienced eye, until you have seen them side by side. The way to learn the difference is to get a few samples of the reproduction glass and compare them to the glass in old windows. After you have done this 50 or 100 times you will know the difference.

It can be interesting to collect samples of the different kinds of glass you are working with. As your collection develops you will learn to instantly recognize the different types: crown, cylinder, float. And, you will also be able to recognize the reproduction glass for what it is--a distant imitation.

_________________
John

by hammer and hand great works do stand
by pen and thought best words are wrought
Back to top
View user's profile Send private message Send e-mail Visit poster's website
Sean



Joined: 27 Dec 2006
Posts: 170
Location: Salem, MA

PostPosted: Thu May 06, 2010 4:28 pm    Post subject: Reply with quote

Here is something that may be of interest. The crown glass glaziers manual from Scotland, 1835.

Daniel Cooper's, Crown Glass Cutter's and Glazier's Manual, Scotland, 1835:
http://books.google.com/books?id=VN5AKdj4QfMC&printsec=frontcover&dq=the+glaziers+manual&source=bl&ots=V6u96w_Yjq&sig=FsvM8le_gwKOcm4W__PJUpVyi-c&hl=en&ei=BTTjS7fWCIL78AbV1tGfDw&sa=X&oi=book_result&ct=result&resnum=3&ved=0CB0Q6AEwAg#v=onepage&q&f=false

Here is a company that will print "on demand" for a pretty reasonable price.

http://www.amazon.com/gp/search?index=books&linkCode=qs&keywords=1141089750

Sean
Back to top
View user's profile Send private message Send e-mail
johnleeke
Site Admin


Joined: 20 Aug 2004
Posts: 2940
Location: Portland, Maine, USA

PostPosted: Thu May 06, 2010 6:01 pm    Post subject: Reply with quote

Wow, excellent find Sean. That's a great book--everything from making glass, building the kiln to dry your whiting to make your putty, and setting the pane. Just be sure to place your pane with the rounded side to the weather!

"To glaze well, neatly and expeditiously, simple as the operation may appear, is an art not to be acquired in a day."

_________________
John

by hammer and hand great works do stand
by pen and thought best words are wrought
Back to top
View user's profile Send private message Send e-mail Visit poster's website
Andy in NH



Joined: 01 Mar 2006
Posts: 92
Location: Lyndeborough, NH

PostPosted: Fri May 07, 2010 6:50 am    Post subject: Reply with quote

A couple more additions. The "20th Century cylinder glass" example is actually a good presentation of the Lubers process, which originated in the 1920's and was in use up through the 1960s in some plants. The original hand blown cylinders were often on the order of 10 to 14" in diameter. The lehrs (annealing ovens) that the glass was placed into had plaster of paris floors to help produce a clean finish. I have found glass where you can see some grit from the lehr had imprinted on the glass and on occaison a mark from one of the wooden tools used to spread the glass as it heats.

Also, there were interim steps to the Pilkington float glass process which involved vertical tower processes where the glass was pulled upward (guided by rollers on the edge) and larger sheets were cut off at the top of the stack (1930's to late 50's).

Seeds (bubbles) can be caused by a mixture not cooking long enough and I have found them in all processes (including plate and sheet glass) up to modern float glass. Rheamy glass can be cuased by variations in mixture and temperature as well as things like parts of the clay crucible breaking off and mixing with the glass to form a harder type of transparent glass.

There were elaborate cutting guides for crown glass so that you could optimize for maximum value in a given table (disk of crown glass). In much the same way that lobsters was once regarded as low grade undesireable food, the bullseyes from crown glass were only used in areas least likely to be looked through and only came into fashion in more modern times.

Glass colors can be affected by local ingredients used. Early glass for the Massachusetts state house was so dark that it caused quite the uproar and had to be replaced. The addition of manganese resulted in purplish glass often found in the Beacon Hill area of Boston. Iron oxides can impart a yellowish green tint (easiest to see on edge). Our local quartz quarry was the source for a brilliant blue glass that was primarily used for bottles but there is some suggestion that some window glass may have been produced. When I went to research formulas, I quickly gave up after seeing that there were literally thousands of variations.

An excellent source for research is the Rakow Research Library at the Corning Museum of Glass. The staff is excellent and extremely helpfull. Many of the materials are also available through interlibrary loan. They are currently undergoing renovations. http://cmog.org/dynamic.aspx?id=168

Andy
Back to top
View user's profile Send private message Send e-mail Visit poster's website
Skuce



Joined: 08 Nov 2009
Posts: 188
Location: Ontario Canada

PostPosted: Fri May 07, 2010 11:02 am    Post subject: Reply with quote

What about the Bendhiem Reproduction glass that claims to be a hand blown equivalent? Comparing it to the original hand blown stuff?

Yes, A lot of the"repro" glass out there is just reheated/modified 1/8" float glass. It's dead obvious when you look at it that it's not hand made.

_________________
Drew Skuce
PSC Heritage Restoration
5-48 Woodslee Ave. Paris, Ont. Canada
www.ParadigmShiftCustoms.com
Back to top
View user's profile Send private message
johnleeke
Site Admin


Joined: 20 Aug 2004
Posts: 2940
Location: Portland, Maine, USA

PostPosted: Fri May 07, 2010 11:46 am    Post subject: Reply with quote

Quote:
What about the Bendhiem Reproduction glass that claims to be a hand blown equivalent? Comparing it to the original hand blown stuff?


The basic method may be the same there are always differences because the glass itself and the worker's techniques and procedures are different, and the human eye is highly tuned to notice such visual effects. Whether or not the difference is important depends on the objectives or criteria of the project. The difference might be too noticeable if the reproduction glass is set in the same sash as the original. But, if you "rob Peter to pay Paul" by shifting all the original glass into the same window and put the reproduction glass all in another window or even another room, then the consistency might make it look acceptable.

Once a customer really wanted the Bendhiem Reproduction glass, but when she saw it in her windows she was unhappy. Now I always provide a sample, and will usually install it to show the difference in the sample window for the project.

Sometimes a closer match can be found with salvaged glass, which is why many of the window specialists keep a stockpile of the original glasses that were used in the area they serve.

_________________
John

by hammer and hand great works do stand
by pen and thought best words are wrought
Back to top
View user's profile Send private message Send e-mail Visit poster's website
johnleeke
Site Admin


Joined: 20 Aug 2004
Posts: 2940
Location: Portland, Maine, USA

PostPosted: Sun May 09, 2010 6:31 pm    Post subject: Reply with quote

Richard Byrne reports:

One of the surest sources of identifiable period glass is in case pieces with glazing. If you
know the date of the furniture's manufacture and the glass is original in its bed, then you have a sound reference. The thing to keep in mind is that seeds and reams, though they tell you something, they do not necessarily tell just what method was used in the glass's manufacture....particularly toward the last half of the 19th and early 20th century.

The Wikipedia entry on crown glass is all bull shit. Who ever wrote it
doesn't know much about how it was made.

- Richard

_________________
John

by hammer and hand great works do stand
by pen and thought best words are wrought
Back to top
View user's profile Send private message Send e-mail Visit poster's website
TimB



Joined: 03 Sep 2009
Posts: 43

PostPosted: Mon May 10, 2010 8:02 am    Post subject: Glassmaking Reply with quote

Here are a couple of nice illustrations showing crown and cylinder glass making. Sorry they aren't better quality. I tried to find images from Denis Diderot's encylopedia... it was published in France in the second half of the 18th century and shows crown glass making in detail.


Cylinder Glass.jpg
 Description:
 Filesize:  19.68 KB
 Viewed:  334 Time(s)

Cylinder Glass.jpg



Crown Glass3.jpg
 Description:
 Filesize:  14.82 KB
 Viewed:  269 Time(s)

Crown Glass3.jpg



_________________
Tim Brosnihan
Back to top
View user's profile Send private message
TimB



Joined: 03 Sep 2009
Posts: 43

PostPosted: Mon May 10, 2010 8:11 am    Post subject: Repairing Glass Reply with quote

While we are on the topic, I am in the process of restoring a pair of 2 over 2 window sash. Some panes are modern glass and some are cylinder glass. Upon removing one piece of glass, I discovered that two small pieces were broken off at the corner. The edge of the breaks project maybe 1/2 inch at the most beyond what will be the edge of the putty when they are finished. I was going to replace the piece of glass until I discovered it was one of the old pieces of cylinder glass. Now I would like to keep it, if possible. Should I simply rely on the putty to hold the broken pieces in place, or should I use some sort of adhesive? The sash is protected by a storm window, so it stays pretty dry.
Thanks for any advice you can offer.

_________________
Tim Brosnihan
Back to top
View user's profile Send private message
johnleeke
Site Admin


Joined: 20 Aug 2004
Posts: 2940
Location: Portland, Maine, USA

PostPosted: Mon May 10, 2010 8:31 am    Post subject: Reply with quote

Tim:

Thanks for the glass making illustrations. What is the source?


Here is the discussion on "healing" broken glass with adhesive:

http://historichomeworks.com/forum/viewtopic.php?t=1321

_________________
John

by hammer and hand great works do stand
by pen and thought best words are wrought
Back to top
View user's profile Send private message Send e-mail Visit poster's website
Display posts from previous:   
Historic HomeWorks Forum Forum Index -> Windows & Doors Goto page 1, 2, 3  Next 
Post new topic   Reply to topic All times are GMT - 5 Hours
Page 1 of 3

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum