The Evolution of
Most of us are aware
that glass has been produced since ancient times. The first glass
vessels date from around 1500 B.C. but it wasn’t until around 30
B.C. that the Romans invented the blowpipe which allowed molten
glass to be blown and spun into thin sections. Manufacture of
colorful glass for use in churches and cathedrals reached a high art
in Europe during the middle ages.
While glass has been
around for thousands of years, the availability of clear glass for
use by the masses is actually a relatively recent development. The
first glass making plant in the United States was built in
Jamestown, Virginal around 1610 but failed within a year. Other
attempts at glass making likewise failed. It wasn’t until 1739 that
a successful glass works was established in the U.S. The plant was
built by Caspar Wistar in Salem County, New Jersey. It operated
until around 1780.
Early glass making
efforts were dedicated to making containers for food, medicines and
liquor. Sheet glass such as is used in windows (and clocks) was not
readily available from American manufacturers until the early
1800’s. Glass at this time was created by attaching a molten lump of
glass to a blowpipe then blowing a bubble into the lump.
The white-hot lump of
molten glass was then spun rapidly and expanded outward to create a
thin round sheet. As a result of the technique, the final sheet
always had a rise or “crown” in the center where the blowpipe was
attached. This glass making technique was therefore called crown
glass. Usually, pane-sized squares or diamonds were cut from the
sheet and the center crown reprocessed. Sometimes, thrifty shoppers
could purchase the center “crowned” portion of the glass at a low
price for use in windows. These are seen from time to time in old
By about 1825 the
crown glass process was replaced by a technique in which the lump of
molten glass was blown into a long cylinder. Once the cylinder had
cooled it was sliced down one side and then reheated. When heated
the cylinder unrolled into a flat plate of thin, clear glass which
could easily be cut into window pane sizes with little waste.
Cylinder glass marked the point at which glass could be produced at
prices that the masses could readily afford. Cylinder glass was the
prevalent technique used in the United States from around 1825 until
making was a radical breakthrough in the production of low cost
window glass. It was, however less perfect and transparent than
modern glass. Because the glass cylinder from which the flat panes
were eventually cut was blown and not pressed there were small
variations in thickness from one area to the next. This produces the
small “waves” often seen in the glass. Additionally, the melting and
mixing process used with early glass was less efficient than modern
glassmaking. As a result, air pockets were not thoroughly removed
from the molten glass and tiny bubbles or “pearls” are usually
apparent in the finished plates.
Glass making in the
1800’s was less efficient and perfect than found today. This however
is the quality that distinguishes true antique glass from its modern
counterpart. Viewing antique glass from a slight angle so that a
reflection can be seen will quickly reveal the uneven surface.
Modern glass, on the other hand, will look perfectly flat and smooth
when viewed in the same manner.
sign of antique glass is the presence of many tiny air bubbles
trapped in the glass.
All glass up to the
introduction of modern pressed-glass techniques (1903) will have
these tiny bubbles.
From the early 1800’s
on colorful tablets were produced using a variety of techniques. The
three most common techniques for creating colored tablets are
The use of
stencils to repeat patterns dates far into antiquity. Earliest use
of stencil use can be found in cave paintings dating to 30,000 B.C.
Ancient Egypt use stencils extensively in tomb decorations and
ancient Greeks created mosaic designs using stencils. The word
stencil comes from the middle-English word “stanselen” which means
“To ornament with sparkle” and the earlier Latin “stansel” which
American colonist, unable to obtain or afford expensive wallpaper or
decorated furniture from Europe, used stencils to decorate both.
From about 1760 until 1840 artist traveled from town to town and
applied stenciled designs to furniture, walls and mantles. One of
the most prolific of these was Moses Eaton jr. (1796-1886) who
created stencils in hundreds of homes in New England in the 1840’s.
Stencils grew in use as the brass movement came into use and clock
production skyrocketed. Early designs tended to be bold geometric
designs but very intricate and complex designs soon followed. Bright
colors as well as gold pigments were combined to produce rich
sophisticated tablets that
contributed greatly to the style of clocks of the period.
The most notable creator
of stencil designs for clock tablets was William B. Fenn of
Plymouth, Connecticut (1813~1890). Fenn worked for Seth Thomas
between around 1830 and 1840 then started
his own business supplying clock tablets to Connecticut clock
manufacturers. Between 1840 and 1864 Fenn was a
major supplier of clock tablets to manufacturers such as Seth
Thomas, Silas Hoadley, Brewster & Ingraham, Birge & Fuller as well
as many others.
Many of Fenn’s most
successful stencil designs have been published by the
Clock & Watch Museum in two books Clock Decorating Stencils
(ISBN 0-930476-17-4) and More Clock Decorating Stencils (ISBN
PUB259) Original Fenn stencils, acquired from the family, were used
to produce the photos in both books. These books are a fantastic and
historically correct reference to stencils of the period.
In the 1830’s an image transfer process was developed wherein
designs were created on metal plates by engravers. The engraver was
able to achieve a level of detail not possible using stencils or
engraved plate was used to print the design in black ink onto very
thin paper. Size or varnish was applied to the glass then the paper
was pressed onto the size once it reached a light tack. The paper
and size were then allowed to cure.
Once cured, the paper
was moistened with water and gently rubbed off leaving the inked
design embedded in the varnish on the glass.
There were several
advantages to the litho-paper process. One: As noted, extremely fine
detail could be produced by the engraver. Two: It could be
inexpensively repeated on clock tablets. Three: Once the black image
outline was applied, colored paints could be quickly added by
non-artist workers to complete the tablet.
With clock production
volumes growing, litho-paper
tablets provided a means to produce a high quality tablet image
with a minimum of cost and effort.
The inks and/or
varnishes used in the process were chemically unstable
and flaking was common problem. Few good examples of this process
Fortunately, there are
ways to reproduce high quality litho-paper tablets using commonly
available materials. Many good images still exist and these can be
used as a resource for recreating a needed tablet design.
Direct Printing to
some point in the 1840’s a new process for decorating tablets was
developed wherein a design was printed directly onto the tablet
glass which had been prepared with a coat of varnish.
Like litho-paper, the
direct-to-glass process used finely detailed engraved plates as the
master for the design. Unlike litho-paper, this process appears to
have been quite stable with many examples surviving today. By the
mid 1860’s stenciled tablets were almost completely displaced by
this new, lower cost process.
process has, from time to time, been referred to as a “Decalcomania”
process. The term Decalcomania comes from the French for "tracing
It was a
practice of transferring colored designs to the skin from damp
paper. This fad reached its peak in France in the mid-1800’s so the
comparison of it to the direct-to-glass printing process is
Tablets produced using
this process are identifiable in several ways. First, the designs
are generally more finely detailed than those achieved with
stencils. Gold detail lines can be quite thin due to the precision
that can be achieved by the original engraver. Detail lines on
stenciled tablets tend to be wider. Secondly, the detail achieved
with an engraved block is usually much greater than can be cut into
a paper stencil. Scenes depicted using the direct-to-glass process
can be quite complex.
Finally, when paint is
lost on a tablet produced using this process the actual design can
usually still be seen imprinted into the underlying size on the
Repair of the
fine-line detail on a decalcomania tablet can be quite challenging,
but there are several modern methods that can be used to make
repairs or completely recreate a missing or broken tablet.
Digital restoration of tablet images can be used to create patterns
or even water-transfer decals that can be transferred to correct
antique glass then backed with with a coat of paint in the correct
color. The results possible using this and similar techniques are
Chapter 10 of Extreme Restoration dedicates around 80 pages to
detailing the various techniques used to decorate glass tablets on
antique clocks. Repair as well as re-creation techniques are
explained and supported by many, many photos.