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Postby johnleeke » Tue Sep 03, 2013 7:50 pm

(update: 5/14/16, PDF file download on cylinder glass, new bent glass source)

[size=150]Types of Window Glass[/size]

[b]Crown Glass[/b] 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: ... 82;num=178

Popular technology; or, Professions and trades.
By Edward Hazen. Vol. 2, p. 178.
[i]"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 centrifugal
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. "[/i]

[b]Cylinder Glass[/b] 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.

Window Glass in the Making, 1926:

20th century cylinder glass production: ... wglass.php

[b]Drawn Sheet Glass[/b]
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

[b]Float Glass[/b] 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.

[b]Reproduction Glass[/b]
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
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
Authentic old glass from the Baltimore and Washington metropolitan area houses that lie in the path of urban sprawl and are slated for demolition

Daniel Goldon Wolkoff
I have tons of old glass 1830 to 1930, including large panes, real large. Boxes of multi panes from 1830 to 1930 available

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

[b]Bent Glass:[/b]

Bent Glass Discussion: ... =3229#3229

Bent Glass Suppliers:

Flickinger Glassworks
Charles Flickinger
175 Van Dyke St., Pier 41
Brooklyn, NY 11231
718 875-1531

Curran Glass Studio
John Curran
6507 Ogden Avenue Berwyn, IL 60402
bent glass in sizes up to 46" x 46" and 29" x 56", hand & machine beveling

Clifford Underwood
Bent Glass Solutions LLC
904 West Broadway
Spiro, Ok 74959
Phone: (918) 315.1566

[size=18]Cutting Glass[/size]

Discussion on glass cutters: ... hp?p=10669

[size=18]Repairing Cracked Glass[/size]

Discussion on taping cracked glass as temporary stabilization method: ... hp?p=10707

Discussion on adhesive methods:

Discussion on foil/solder and lead came methods:
Window Glass in the Making, a 1926 booklet that describes making cylinder glass as done in the late 19th century through the 1950s, with illustrations.
(7.28 MiB) Downloaded 471 times

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