AN IMPROVED PROCESS AND COMPOSITION WHEREBY WOOD, SLATE, AND VARIOUS OTHER MATERIALS ARE MADE TO SERVE AS SUBSTITUTES FOR LITHOGRAPHIC STONES
Year: 1871

page_text: PROVISIONAL SPECIFICATION left by John Newton Lambert at the
Office of the Commissioners of Patents, with his Petition, on the
27th April 1871.
I, JOHN NEWTON LAMBERT, of Castle Street, Bristol, Lithographic
Artist, do hereby declare the nature of the said Invention for "AN
IMPROVED PROCESS AND COMPOSITION WHEREBY WOOD, SLATE, AND VARIOUS OTHER
MATERIALS ARE MADE TO SERVE AS SUBSTITUTES FOR LITHOGRAPHIC STONES," to be
as follows:
It is well known that the ordinary stones heretofore employed in
lithography in addition to being very costly are extremely inconvenient
to manipulate by reason of their weight and are moreover very liable to
breakage and other injuries.
The object of my Invention is the substitution for the aforesaid stones
of some cheap and easily obtainable substances, such as wood, slate,
or various kinds of common stones not hitherto used for such a purpose,
but which by my Invention may be made to serve instead of the more
expensive stones above mentioned. I however prefer to use wood, as
it is more casily prepared, more convenient in use, and less liable to

page_text: injury than any other material, and I will therefore in the following
description more particularly refer to the use of wood for the purpose
of my Invention, although I wish it to be distinctly understood that
the process will be substantially the same when other substances are
used in place of wood. I take a block or slab of wood made smooth
and true by planing or otherwise, I find that birch, deal, elm, or box
will answer the purpose well, but other kinds of wood may be used if
desired. I first coat the same with glue, albumen, size, or other
gelatinous matter, using the one of these substances best adapted to the
particular kind of wood used. In some instances I add to the
gelatinous matter a solution of silicate of soda and bi-chromate of
potash, or I may use this solution without the gelatinous matter. The
block or slab of wood thus coated is then exposed to sunlight cither
diffused or direct to fix the coating, and render it insoluble in water.
The time required for this exposure will vary according to the nature
of the wood and the amount of light, or the precise quality of the
coating required. After it has been thus exposed for a sufficient time
the block or slab is washed to remove from it the superfluous portion of
the coating, then-after-being-thoroughly-dried-the-said_block_or_slab
is ready for use, and its surface thus prepared will be found in all
respects equal to a lithographic stone for drawing or writing upon
or for receiving transfers and other work. As however the ordinary
composition known as lithographic ink will not serve for writing or
drawing upon the wood or other substances prepared as above described
I make an ink or pigment with the following composition:-I take
gelatine, albumen, or other gelatinous matter and dissolve the same in a
saturated solution of bi-chromate of potash, either with or without
chrome alum. To this composition I add a small quantity of ivory
black, lampblack, or other colouring matter to render the ink or
pigment visible while being used, and in some cases I also add a small
quantity of soap to the composition. I then produce on the prepared
block or slab the required picture, design, plan, or other work with this
ink or pigment and allow the same to dry. The drying may in some
cases be finished in an hour or two hours, but in other cases it may
take from twelve to twenty-four hours. When the drawing, writing,
or other work has been thoroughly dried I expose the same to diffused
or direct sunlight to fix and harden it. The time of exposure will
depend upon the amount of light and the precise tint or tone required.
In a bright sunlight a few minutes will be sufficient, but in a diffused

page_text: light and in certain conditions of weather a longer time will be
necessary. I vary the tints by arresting the action of the light at
shorter or longer intervals of time. After this exposure I cover the
surface with gum or glycerine which is absorbed by the portion of the
prepared surface not covered by the ink or pigment. The block or slab
is then ready for the printer who can print from it in an ordinary
lithographic press, or if desired the wood block or slab by reason of its
clasticity can be used in an ordinary typographic press or machine.