An Improvement in Printers' Overlays and in the Process for Making the same.
Year: 1898

page_text: Date of Application, 4th Oct., 1898-Accepted, 10th Dec., 1898
COMPLETE SPECIFICATION.
An Improvement in Printers' Overlays and in the Process for Making
the same.
A communication from abroad by THE DITTMAN OVERLAY COMPANY, of the City
of New York, State of New York, United States of America.
I, WILLIAM LLOYD WISE, of 46, Lincoln's Inn Fields, in the County of
London, Consulting Engineer and Chartered Patent Agent, do hereby declare the
nature of this invention and in what manner the same is to be performed to be
particularly described and ascertained in and by the following statement:-
This invention relates to the art of printing and therein to that part of the pro-
cess of "making ready "known as the construction of the "overlay."
Heretofore overlays have been constructed from layers or sheets of paper of
various thicknesses and texture built up on the "foundation sheet" to give the
desired graduations of impression upon the plate or form.
Another process reported but little used consists in applying a paint to the
foundation sheet in layers of varying thickness corresponding to the graduation
of impression desired.
The object of the present invention is to construct an overlay in a manner such
as to secure a graduation of impression far more accurate and effective than can
possibly be secured by the old processes, and to produce the perfected' overlay in
an interval of time measured in minutes whereas formerly the time for making one
consumed hours and even days.
With this object in view the invention consists in an overlay and the process
of making the same as hereinafter fully set forth.
In making ready" in connection with this improved overlay, the ". underlay"
and preparation of the tympan are effected in the usual and well known manner,
this invention being concerned simply with the construction of the overlay.
In its construction, a suitable foundation sheet, such for instance as has here-
tofore been used as the basis of paper overlays, is "pulled" or given an impression
from the plate or form. Then it is taken from the tympan while the ink
or other impression material is fresh and placed face downward upon a layer of fine
powder evenly spread over some suitable surface, preferably one that is plane and
smooth. The sheet is then pressed down upon the powder by passing the hands
evenly over it or by using any other means suitable for the purpose such as a roller
or rollers. This causes the powder to adhere to the inked parts of the sheet in
proportion to the amount of ink upon the respective parts. Where the ink is
heaviest, there will be the most powder and where there is the least ink there will
be the least powder.
The overlay at this stage is then replaced upon the tympan or platen, and a sheet
of paper having been placed over the plate or form, the overlay is "squeezed" to
thoroughly impregnate, with the ink, the powder that has been picked up by it.
By this means the ink and powder are formed into a paste which adheres
tenaciously to the foundation sheet and which is thicker in the places which register

page_text: with the dark spots of the cut and grows gradually thinner towards the light spots
thereof. For certain grades of the work this step of the process may be omitted,
also with paste or compounds which are only slightly compressible the squeezing
on the plate or form may be as well omitted.
The overlay is then placed in a suitable oven or heater and baked until the paste
is thoroughly hardened which takes but a few moments. Then all loose particles
of powder are brushed off and a light coat of varnish is applied to the overlay when
it is again placed in the oven for a moment and baked or dried. This varnish is
preferably thin and sinks somewhat into the paste thereby insuring closer and
firmer adhesion of the particles of the powder at the surface of the paste thus
making the overlay smoother, harder and more durable.
The overlay as it comes from the second baking may be put immediately into
use but it may be rendered more perfect by passing a straight-edge over the pre-
pared surface to remove any grains or particles of the powder that may have been
raised or left on the surface of the paste or foundation in the application of the
varnish. After passing the straight-edge over it, the surface can be still more
improved by brushing it with a rather stiff brush.
The above is in the main the process as practiced, though there are some details
and refinements of the process which will now be mentioned.
.
It is best in taking the impression upon the foundation sheet to repeat it two or
more times as by this means the sheet is more thoroughly and evenly inked.
Better results are also obtained by squeezing the freshly powdered overlay several
say four or more-times, thereby insuring the proper intimacy of the powder with
the ink.
As will be clearly seen from the above those parts of the overlay which received
the most ink, namely those which register with the dark parts of the cut, will have
the thickest layer of paste and all other parts, for the same reason, will have layers
of paste proportionate to the degrees of darkness of the different parts of the cut,
and the squeezing of the freshly powdered overlay will tend to intensify his
gradation of the different portions of the paste. By this means of preparation,
it is positively assured that the parts of the cut which require the most color and
most impression will get them and those which need less will receive their propor-
tionate amount.
Pulverulent materials or powders of various kinds and composition may be used
in carrying out this invention, but wheat flour has been found to give the best
results of all powders that have as yet been tried. The paste produced from it
becomes extremely hard and yet retains an elasticity which enables an overlay to
stand up under heavy pressure and innumerable impressions in a remarkable
manner and to excel all known overlays in longevity and clearness of impression.
Furthermore wheat flour on being wet by the ink and baked expands and so
materially increases the bulk of the raised portions of the overlay.
The ink best adapted for use in the construction of this new overlay is of a viscid
nature and may be produced by mixing printer's gloss varnish with any of the well
known viscid inks of commerce. Such mixtures may be made in varying propor-
tions but so far as tried the best results are obtained when three parts of the fresh
ink are mixed with one part of the fresh varnish. Other viscid substances and
other powders than the above mentioned may be found to serve the purposes of this
process of constructing an overlay, therefore, this invention is not limited to the
use of the precise ingredients nor to the proportions of the ink which enter into the
formation of the paste or compound employed in building up the overlay.
The viscid compound or paste may be applied to the foundation sheet in other
ways and conditions than those described and still be within the spirit of this
invention.
The surface of the overlay may be finished in other ways than by a coat of
varnish. For instance a sheet of thin strong paper may be applied thereto by
any suitable adhesive and while damp be squeezed down upon the plate or form.
Likewise the powder may be applied to the freshly impressed foundation sheet

page_text: in a different manner from that described as by sifting it thereon and its intimate
association with the ink or other substance by which the impression is made may
be produced in a different manner than that outlined and yet the spirit of the
invention would not be departed from, the gist of the invention lying in using
the difference in amount of the viscid material or ink left upon the foundation
sheet in taking an impression from the plate or form as a means for graduating the
thickness of the overlay and in the use of a pulverulent material having a high
degree of expansibility when moistened and an enduring hardness and toughness
when baked.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed, I declare that what
I claim is:
1. The process of forming an overlay, consisting in constructing the raised
portion thereof from a viscid compound impregnated with wheat flour and hardened,
substantially as set forth.
2. The process of forming an overlay, consisting in making an impression on the
foundation sheet, adding pulverulent material to the substance in which this
impression is taken, and hardening the compound or paste so formed.
3. The process of forming an overlay, consisting in making an impression on the
foundation sheet with viscid material, then adding a powder to said material in
quantities proportionate to the amounts thereof on different parts of the sheet, and
then hardening the compound so formed.
4. The process of forming an overlay, consisting in making an impression on
the foundation sheet, adding a powder to the material of said impression, squeezing
the freshly powdered overlay upon the plate or form and baking the overlay for the
purpose set forth.
5. The process of forming an overlay, consisting in making an impression upon
the foundation sheet, adding a powder to the material of said impression, baking
the overlay, and then varnishing it for the purpose set forth.
6. The process of forming an overlay consisting in applying a paste to the
foundation sheet in suitable locations to register with the raised parts of the plate
or form from which an impression is to be taken and in quantities proportionate
to the pressure desired upon said parts for the purpose set forth, then squeezing
the overlay upon said plate or form and then hardening the paste.
7. The process of forming an overlay, consisting in taking an impression from
the plate or form in a viscid compound, mixing powder in the compound of the
impression by laying the sheet face downward upon a powdered surface, squeez-
ing the freshly powdered overlay, baking it, removing therefrom loose powder,
varnishing it, baking again, and then removing any roughness from the surface of
the overlay, substantially as and for the purpose set forth.
8. The process of forming an overlay consisting in constructing the raised por-
tions thereof by means of a viscid material and a starchy powder, graduating said
portions to the intensity of tone desired, and then hardening them, substantially
as set forth.
9. An overlay consisting of a suitable foundation sheet having raised portions
thereon located and formed in a manner to produce the desired intensity of tones
in the impression, and consisting of a compound of wheat flour and a viscid sub-
stance hardened and having a protective coating applied thereto.
10. The process of forming an overlay, consisting in making an impression on the
foundation sheet with viscid material, then adding a powder to said material in
quantities proportionate to the amounts thereof on different parts of the sheet,
and then hardening the compound so formed.
11. An overlay having the raised portions of its surface formed of a viscid ink
impregnated with powder compressed and hardened by baking.
12. An overlay the raised portions of which consist of a paste or compound
formed from a viscid substance and wheat or similar flour.

page_text: 13. An overlay consisting of a foundation sheet, having the raised portions
thereof formed of a paste made of wheat flour and a viscid ink compressed and
baked.
14. An overlay consisting of a foundation sheet having raised portions thereon
formed from a viscid compound impregnated with a fine powder and baked aud
varnished, substantially as and for the purpose set forth.
15. An overlay having the raised surface thereof formed from a hardened plastic
substance graduated in thickness to correspond to the intensity of the tones in the
plate or form through the manipulation of said substance by the said plate or form.
16. The process of making an overlay consisting in taking an impression or
impressions upon a foundation sheet in a suitable viscid substance, adding a
powdered material to said substance, and hardening the mixture so formed, the
thickness of the mixture upon different portions of the sheet being graduated by
the amount of said viscid substance taken from the plate or form, substantially
as set forth.
17. The overlay and process of making the same, substantially as hereinbefore
set forth.
Datod this 4th of station 1000
W. LLOYD WISE,
46, Lincoln's Inn Fields, London, W.C.,
Chartered Patent Agent.