IMPROVEMENTS IN THE MANUFACTURE OF GLASS
Year: 1838

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JAMES
TIMMINS CHANCE, of Birmingham, in the County of Warwick, Glass Manu-
facturer, send greeting.
WHEREAS Her present most Excellent Majesty Queen Victoria, by Her
Letters Patent under the Great Seal of Great Britain, bearing date at West-
minster the Twenty-first day of April, in the first year of Her reign, did, for
Herself, Her heirs and successors, give and grant unto me, the said James
Timmins Chance, Her especial license, full power, sole privilege and authority,
that I, the said James Timmins Chance, my exors, admors, and assigns, or such
others as I, the said James Timmins Chance, my exors, adiñors, or assigns,
should at any time agree with, and no others, from time to time and at all
times during the term of years therein expressed, should and lawfully might
make, use, exercise, and vend, within England, Wales, and the Town of
Berwick-upon-Tweed, my Invention of "IMPROVEMENTS IN THE MANUFACTURE
OF GLASS," in which said Letters Patent is contained a proviso, that I, the said
James Timmins Chance, shall cause a particular description of the nature of
my said Invention, and in what manner the same is to be performed, to be
inrolled in Her said Majesty's High Court of Chancery within six calendar
months next and immediately after the date of the said in part recited Letters
Patent, as in and by the same, reference being thereunto had, will more fully
and atlarge appear.
NOW KNOW YE, that in compliance with the said proviso, I, the said
James Timmins Chance, do hereby declare that the nature of my Inven-

page_text: tion, and the manner in which the same is to be performed, are fully described
and ascertained in and by the following statement thereof, reference being had
to the Drawings hereunto annexed, and to the figures and letters marked
thereon, that is to say :-
My Invention relates, first, to a mode of smoothing and polishing thin sheet
glass which will not allow of being ground away, in order to obtain the same
in level planes, as is the process of manufacturing plate glass, which being cast
or blown of considerable thkicness will allow of inequalities caused by con-
cavities and convexities and bendings or curvatures of a general substance, as
well as other little irregularities of surface of a sheet of glass, being ground away,
in order to produce two level planes for surfaces, which are then smoothed and
polished, as is well understood by plate glass manufacturers; the object of my
Invention being to remove the irregularities of surface, without grinding away
irregularities arising from any bendings or curves, which may exist in the general
substance of the glass; and thus I am enabled to smooth and polish thin sheet
glass, which will be found valuable for glazing of windows, engravings, and
pictures, and other useful purposes, having an appearance in most cases
equal to, and for some purposes, such as glazing pictures and prints, in con-
sequence of its thinness, even superior to the plate glass now manufactured, at
the same time avoiding the great weight which is necessarily given to plate
glass, in order that it may be of a degree of thickness which will allow of
grinding away, not only surface irregularities, but also curves; bends, and other
inequalities in the substance of the glass.
And, secondly, my Invention relates to an improvement in the manufacture
of that description of glass called crown glass. It is well known that in the
manufacture of crown glass there is produced a thick ring or external boundary
to the tables of crown glass, which not only materially adds to the weight of
each table, but is, in fact, prejudical to the appearance of the corner of a
square of glass cut from a table, unless the ring or thick boundary of the table
be removed and cut to waste.
Now, the object of the second part of my Invention is to prevent or reduce
the enlarged thickness of the boundary of the circumference of tables of crown
glass in the process of making such description of glass.
Having thus generally pointed out the nature of my Invention, I will
proceed to explain the processes I pursue for carrying the same into practice.
The kind of glass I prefer to operate on, according to the first part of my
Invention, is what is called German sheet glass, which can be produced in
large sheets, as is well known, and is made by blowing glass into hollow
cylinders, and by cutting in a line parallel with the axis, and by subsequent

page_text: heat; each cylinder is laid open into a sheet, and is annealed; but such glass,
by the act of its being laid into sheets, has certain irregularities of surface pro-
duced which did not exist when in the form of cylinders; there are also other
irregularities in the general substance of the glass, it at all times retaining
more or less of a bended or curved substance, however carefully and repeatedly
the flattening process may be performed, which bending of the substance of the
glass will, in many cases in large sheets, be found to be equal (when the
sheets are laid on truly plain surfaces, to,) and in some cases exceed, the thick-
ness of the glass, consequently such glass would not allow of grinding away
to obtain even planes, nor will such thin glass allow of grinding away of much
of the substance when the bending or curve, or such like irregularities, are to
a much less degree than the thickness of the glass itself, and at the same time
the thickness of such glass does not materially vary throughout a large sheet,
but for practical purposes may be said to have parallel surfaces when the small
irregularities of surface produced by bending a cylinder into a sheet are not
taken into consideration, which latter it is required to have removed, in order
to obtain good smooth polished surfaces to such glass, leaving the curves or
bends which exist in the substance of the glass much the same as before under-
going the smoothing and polishing processes.
DESCRIPTION OF THE PROCESS.
The first point to be obtained in treating such glass is to cause it to lie in a
level plane, by taking advantage of its capability of being bent and laid even on
level planes, as hereafter explained.
I take a sheet of glass which has been flatted by the ordinary means, in
order to get the same as even as possible, and diminished as to its original size
no further than what is necessary to make its shape rectangular. This sheet is
laid on a table or surface prepared as follows:-A slate or other suitable
surface of about the same superficial dimensions as the glass, and about five-
eighths of an inch thick, is mounted on a wooden frame, and is ground down to
a level plane. The slate is then covered entirely with a piece of leather of
uniform thickness (or other suitable material), previously soaked in water. The
glass, when laid on this level or plane surface, will seldom, if ever, lie flatly, so as
to touch at all parts upon the table, but as the glass is flexible to a considerable
extent, and may be readily bended, it is capable of being pressed down close to
the damp bed or table by commencing pressure at one edge, and passing over
to the other, in a somewhat similar manner to the action used in pasting a
sheet of paper on to a level surface, and all air being thereby driven from
under and excluded from between the glass and the bed or table on which it is
.

page_text: laid, the glass will be retained in this flat position by the weight of the super-
incumbent atmosphere, which, for ordinary thicknesses and curvatures, will be
found sufficient to resist the elastic power which the glass possesses of resuming
its natural form, and thus will a sheet of thin glass be obtained in a suitable
plane for performing the process of smoothing and polishing, which is a mode
of treatment very different to that employed in fixing (for grinding) plate glass,
the grinding process applied to plate glass being in fact for the purpose of
obtaining a plane surface by grinding away the substance thereof; but when
a plane surface of glass is obtained to the thin glass, as above described, and
when a plane surface has been obtained by grinding away the substance of plate
glass, the processes of smoothing and polishing are very similar for each
description of glass, the variation of the processes being to accommodate them
to the peculiar nature of the thin glass, and the mode of laying and holding
the same in a plane surface whilst being acted on, such plane surface not being
retained by the thin glass when removed from the table; whereas, the plate
glass being ground away into plane surfaces retains such planes after taking
them off the table where they have been operated on. The substances which
I prefer to use for the purpose of smoothing are emeries of six or seven
degrees of fineness, obtained by grinding emery stone, and separating the
different kinds by washing with water, in the usual manner, or in place of the
coarser emery very fine sand may be used. Two sheets of glass are laid flat
on damp level beds, as above described, and one table rests stationary in a
horizontal position on a fixed vertical frame, and the other one being carefully
reversed is laid glass against glass upon the other, and is then attached to the
smoothing machine, as will be hereafter more particularly described, or the two
surfaces may be worked by hand labour.
In employing machinery for performing the process of smoothing, the
arrangement should be such that a line which bissects lengthways any
horizontal section of the upper table, the centre of this line should be con-
strained to move in a straight line, while a point in the same line at a certain
distance from this centre is made to describe a circle; the radius of such circle
is arbitrary.
The machine being in motion, the workman commences with the coarsest
emery powder or very fine sand; this he sprinkles on the lower glass, and assists
its action by water. This operation is continued until both the glass surfaces
in contact appear to be uniformly rubbed. The same process is repeated with
each of the remaining emeries, which are used in the inverse order of their
respective degrees of fineness. Each emery should be used until it has
obliterated the scratches produced by the preceding one.
The two sheets of

page_text: glass are afterwards turned and relayed by taking advantage of the bending
properties, and their remaining faces or surfaces are treated in the same
If any defects of surface are observable when the glass leaves the
smoothing process, the workman is to rub them away by hand, using for this
purpose the finest emery and a small piece of glass. In removing a sheet of
glass from a table, one of two modes may be resorted to:-First, by carefully
lifting one edge and allowing the air to enter between the table and the sheet
of glass till the whole surface is removed from the table, thus taking advantage
of the bending capabilities of the glass, or the sheet of glass may be slided off
A thin sheet of glass is laid, as before explained, on a table covered with
leather or other suitable material. The rubbers are prepared in the following
manner:-A piece of wood (about 8 x 3 x 14 inches) is covered on one face
with felt, a liquid or paste is made by mixing crocus or the red oxide of iron with
water; this paste is rubbed upon the felt or thrown on to the glass by means
of a brush or otherwise, and the rubbers are made to produce an uniform
polish over the glass by hand, or by means of machinery.
DESCRIPTION OF THE DRAWINGS OF MACHINERY FOR SMOOTHING
THIN SHEET OF GLASS.
Fig. 1 represents a front view of a smoothing machine. a, a, is a fixed
horizontal table, having a sheet of thin glass laid on the upper surface thereof,
as above explained; and b, b, is another table, having a sheet of glass laid on
the under surface. The two surfaces of glass being parallel, owing to their
being held in contact with two hard plane surfaces of the tables a, b, by taking
advantage of the capability such thin glass has to bend, and to be laid even
and retained in contact with the planes of the tables by the weight of the
atmosphere resisting the glass assuming an irregular surface when it has been
once smoothly laid and all the air driven out from between the glass and the
table, hence the glass is at all parts kept in contact with the table and parallel
with it, thus producing suitable plane surfaces to be rubbed together in
the process of smoothing, which would not be the case if the ordinary means
were resorted to for holding such thin sheets of glass as are pursued in holding
sheets of plate glass, where level planes are obtained by grinding away the
glass, and retaining such level planes without reference to the bed on which
the glass is laid. b, b, is the framing of the machine, which should be strong
and without vibration; c, c, are the legs of a platform, on which the stationary

page_text: table
is supported; d is an upright axis, turning in suitable bearings or
brasses at e, e; and f, f, are pulleys for an endless band from a steam
engine or other power, to give rotatory motion to the axis d, such pulleys
being placed on the axis d; and g is a clutch box capable of sliding on
the axis d on a feather, as is well understood; h being a lever by which a
workman can put the clutch box into or out of connection with the pulleys,
and consequently start or stop the machine. On the lower end of the
axis d is affixed a crank i, as is shown in the Drawing. j is a bar having
four openings; in the first opening is placed the crank pin k, by which
the movement of the crank is connected with the bar j; but such movement
of the bar is controlled in the following manner:-1, 1, are two uprights affixed
to the framing of the upper table 6, which enter two of the holes or openings
in the bar j, the bar being affixed to those uprights by set screws, as shewn, or
otherwise; m is a bar which moves in bearings or guides n, n, and by such
guides are controlled to move in a right line; o is an axis descending from the
bar m, and enters the bar j, and allows of the bar j turning on that axis; hence,
in the revolution of the crank i, the bar j is moved also, but the movement of
the bar jis thus regulated and controlled by the axis o, which is in the centre
of the upper table, moving at all times to and fro on a right line; by this
means a compound movement will be obtained to the. upper sheet of glass,
compounded of the revolving motion of the crank and the right line movement
of the axis o, about which the sheet of glass turns, as will be evident on

page_text: set screws D, as is clearly shown in the Drawing. The frames Care capable of
moving to and fro in the dovetail grooves formed in the guides E, which
are carried by the framing of the machine, such dovetail grooves having
filling pieces capable of being set up by screws, as is shewn; hence, the
dovetail projections on the under side of the frame C work correctly in the
grooves of the guides, and are retained in those guides by the filling
pieces. F, F, are connecting rods, which are connected to the frames. C
by pin joints, as is shown by dotted lines, the other ends of such con-
necting rods move on axes at F', and have collars or straps which embrace
excentrics affixed on the shaft G, as is clearly shewn; the shaft G turning
in suitable bearings at H, carried by the framing of the machine;
hence, when the shaft G receives rotatory motion, as hereafter described,
motion is communicated to the tables C. And motion is communicated
to the machine in the following manner:-I is a wheel, only partly shewn
in the Drawing, which is driven by a steam engine or other power, the
wheel I, taking into the wheel J, gives rotatory motion thereto. The
wheel J being affixed on the axis K, there being a worm or screw affixed
on the axis K, which drives the wheel L affixed on the shaft G, thus is
motion obtained to the shaft G, and from it to the tables C; on the axis
K, are formed two cranks M, N, which, by means of connecting rods P, Q,
give motion to two rocking levers R, there being two levers R at each end
of the machine, combined together by screw bolts T. From the upper parts of
the rocking levers R proceed connecting rods V and W, W, such connecting
rods being attached by pin joints to the frames X, Y, which carry the
polishing surfaces Z, the frames X, Y, being carried in guides a which
retain them upright. The polishing surfaces Z are applied to the frames
X, Y, in the following manner:-Z' are projecting rods from the tops of
the polishing instruments, which pass through guides Z' in the frames,
there being a set screw to each rubber, in order to retain it up from the glass,
when desired, such set screw passing through one of the guides Z', as shown.
On each side of the bars Z' is a projecting stud, which is pressed on by
a lever Z³, having its axis on a polishing frame, such lever being borne upon
by a spring Z, which is affixed to the frames X or Y, one spring to each
polishing instrument, and there is a set screw passed through each spring by
which the degree of pressure is regulated. The machine, when set to work,
will evidently cause the polishing intrements Z, carried by the frame X, to move
at all times in an opposite direction to the polishing instruments on the
frames Y, which is important where the glass is held level, according to the

page_text: means above described. In working this machine the workman puts on
the polish mixture from time to time by a brush or otherwise.
Having thus described the nature of my Invention, and the manner in
which the same is to be performed, I would remark, that I make no claim
to any of the parts of the machinery, or the combinations thereof, which have
been before used either for the polishing of glass or other purposes, and I am
aware that attempts have been made to grind smooth and polish square or small
sheets of thin glass by pursuing like means to those resorted to for grinding,
smoothing, and polishing plate glass, but I believe without success. I do
not claim the grinding, smoothing, and polishing thin glass generally, but only
a mode of doing so, as herein described.
I will now proceed to explain the mode of preventing or reducing the
enlarged external edge or boundary of tables of crown glass. In making
crown glass, as is well understood, a solid mass of metal (melted glass) having
been collected at the end of a hollow pipe (as shewn at Fig. 5), is expanded
by the operations of "marvering" (or rolling on a flat metallic slab), blowing,
and heating into a hollow spheriodal globe, which is joined to the pipe by
a hollow cylindrical piece of metal (A), termed the neck. The globe being
completed, a rod, named a punt, is attached to the bullion or part B of the
globe, which is exactly opposite to its neck, and this neck being broken
transversely, in order to disengage the pipe, a circular aperture is left of
about two to three inches diameter. The hollow globe of metal is then
exposed to the flames of an open fire, and the punt which holds it being
twirled or revolved round in the workman's hand, as is well understood. The
globe is spread by centrifugal force, and a table or circular plate is produced,
the neck forming the periphery or external boundary or ring of the table.
Now, the thickness of this selvage is generally much greater than that of
the rest of the table, excepting the bull's eye or central portion, and the
adjacent parts, a circumstance which both increases the cost and diminishes
the value of the glass. The thickness of this selvage depends on the diameter
and substance of the necks, and varies, as they vary.
The nature of my improvement consists in the reduction of the thickness
of the said selvage by diminishing, with much greater certainty than can be
attained by the present modes, both the diameter and substance of the neck,
and this latter diminution is effected by the simple contrivance of turning or
rolling the neck, while in a hot ductile state, on a wooden bar or surface.
Having selected a piece of soft wood, such as that of the pear tree, I cause
a bar to be cut from it about six feet long, six inches wide, and one inch

page_text: thick, and on one edge of this bar are cut, transversely to its length, small
grooves (to receive the necks) at convenient intervals, about two inches wide
by three-quarters of an inch in depth. This bar is placed with one face
close against that edge of the blowers "marver," which is furthest from and
opposite to the workman, the grooved edge being uppermost, and about three
inches above the top of the marver, and it is fixed in this position horizontally
in such a manner that one end of the bar is moveable on an axis, while the
other end rests on a pin, which may be removed and replaced at pleasure.
Suppose, then, that the blower is about marvering a globe before the process,
the boy who attends on purpose removes the pin, and allows the bar to drop
below the marver, but when the blower has finished the marvering, the boy
raises the bar into a horizontal position, and replaces the pin beneath it, and
the blower having placed the neck of the globe on one of the aforesaid
grooves, turns it round in the same, and continues blowing until both the
diameter and substance of the neck appear to be sufficiently reduced, which
the workman with a little practice will readily judge of, the boy then drops the
bar, and the boy, during the interval between two operations, ought to wipe
the marver clean from the small particles which escape from the wood, and
also keep the edge of the bar moistened by a wet sponge.
In witness whereof, I, the said James Timmins Chance, have hereunto
set my hand and seal, this Nineteenth day of October, One thousand
JAMES TIMMINS CHANCE. (L.S.)
AND BE IT REMEMBERED, that on the Nineteenth day of October, in
the year of our Lord 1888, the aforesaid James Timmins Chance came before
our said Lady the Queen in Her Chancery, and acknowledged the Speci-
fication aforesaid, and all and every thing therein contained and specified,
in form above written. And also the Specification aforesaid was stamped
according to the tenor of the Statute made for that purpose.
Inrolled the Twentieth day of October, in the year of our Lord One
'thousand eight hundred and thirty-eight.