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Dec- 17, 1946-
Filed Feb. 16, 1945
// —- Molar Pandas
{'W ;M
Patented Dec. 17, 1946
- 2,412,889
Edward Jahoda, Detroit, Mich'., "am; to
Walter M. Fuchs, Detroit, Mich.
Application February 16, 1945, Serial No. 578,187
1 Claim. (01. 101-1493)
This application relates to the art of printing,
However, I observed that if the gelatin coating
using the retro-gelatin printing process. '
were to be used at ordinary room temperatures,
which in warm weather may exceed 975° F., good
In that process, an original whose image lines
contain a primary chemical, such as potassium
dichromate, is caused to- engage a moist gelatin
reproduction results would be diillcult to obtain.
Consequently, in warm weather, it would be
coated plate, the coating being sensitized by the
necessary to maintain low room temperatures and
inclusion therein of a secondary chemical, such
this would be costly and diil‘icult and annoying.
as ferrous sulphate. The contact of the original
Therefore, I contemplated loading the gelatin
image with the ferrogelatin coating causes the
with a body hardener or tanning agent, such as
engaged portions of the ferrogelatin coating to 10 formaldehyde, or chrome alum, but this also
be chemically a?ected or hardened selectively
would be unsatisfactory. Ii’ little tanning agent
and super?cially, that is, only on the surface,
were used, the gelatin coating would not become
to form against the una?ected parts of the
sufficiently tanned except after being “aged" or
ferrogelatin coating, which remain soft or un
"cured” by storing the coated paper for a long
hardened, a super?cial image whose lines are 15 time, to attain su?lcient tanning. Thereafter
oxidized or dulled or hardened. v'I'he hardening
the coated paper would be usable, provided not
which forms the image is merely super?cial and
too long a time elapsed before use: otherwise
- selective, that is to say, the hardening occurs
the coating would become excessively water re
only at points where the markings of the original,
pellant. It‘ is observed that excessively tanned
containing the primary chemical, make contact‘ 20 coatings would not function well inthe process,
with the gelatin, but is sufficient to have a greater
primarily because, of the lack of capacity to ab
affinity for greasy printer's ink than the back
sorb su?icient water for good reproduction. On
ground which, when su?lciently moist, has‘ no
the other hand, if much tanning agent were used,
such affinity.
the coating would tan quickly, but this would
, It is known that, in printing with a ferro
require immediate use of the paper, and this,
gelatin coated plate so affected by an original
image, hereafter known as a printing plate, it
is desirable to keep the gelatin coating surface
would not always be feasible. In addition, the
use of tanning agents would reduce the quality
moist, that is, to maintain what is technically
In this application, I disclose a solution to the
30 problem of maintaining water balance, now en
called a “water "balance" for such surface.
One way of maintaining such water balance
and ease of reproduction.
countered in the art of printing by the\i'erro
I is to provide a high humidity for the room. This
gelatin process. Brie?y, it may be character.
has obvious disadvantages, but is an accepted
ized as using a paper printing plate and wet
ting it from the back, the moisture passing
Another way of maintaining water balance, is 35 through the plate to the printing surface. This
to apply water to the printing surface by spray
way of maintaining water balance is extremely
ing or otherwise wetting it directly. This is not
effective and desirable. Using this vway, it is
desirable, because it has been discovered that
unnecessary to control the humidity of the room
when water is applied directly to the printing
in which the printing is being done, nor is it
surface, it has a tendency to spread unevenly, 40 necessary to wet the printing surface from the
and also to emulslfy with.the ink.
front,‘ and run the risk of emulsifying ‘the ink.
A third way is to load the gelatin with a hygro
The invention may be practiced by providing,
scopic material such as glycerine. This is also
as the printing plate, a thin sheet of water ab
undesirable since glycerine coated materials are
sorbent, wet strength paper, coated with gelatin
di?cult to handle and store.
In commercial practice, particularly where a
gelatin coating is spread on a supporting table
45 and laid down on a moist smooth rubbing pad.
in a humid room, it is common practice to scrape
oil or otherwise remove the gelatin coating fairly
frequently, let us say, after a few hours of use, "
and to spread a new and fresh coating. ‘This
has obvious disadvantages but it has been ac
cepted as part of the practice in this art.
Now, I have contemplated using, as the gelatin
printing plate, a‘ paper sheet coated with gelatin. 55
The paper sheet provides an economical, renew
able, inexpensive to discard, stable, printing ‘
plate, which is not only superior to presently
known plates because it may be wetted from the
back, but in addition, can be renewed quickly,
inexpensively, and very conveniently, after its
gelatin coatinghas had its effectiveness destroyed
by the changes whichhave taken place in it
during the printing operation.
The present invention is also directed to the
With gelatin. the usual plasticizers, ?ller, etc.,
problems of making the printing plate, that is,
coating the paper, in a manner that permits the .
-all well known to the art, may be and preferably
coated paper to be stored inde?nitely, used when
, should be incorporated within the coating. How
ever, little or substantially no tanning agent in
ever desired, and used at ordinary room temper
atures even in warm weathen?and to the use of
corporated; thus the paper does not deteriorate
with age after the coating is tanned, and the
paper is usable immediately after being coated,
such coated paper for reproduction, at ordinary
room temperature, even in warm weather.
Brie?y, the coating herein disclosed is sub
stantially untanned, having little or no tanning
for/it is not necessary to age it or cure it to the
point of tanning of the coating.
agent. Kept dry, it may be stored indefinitely. 10 ' Though the gelatin coating is to be utilized in
the ferrogelatin process, it need not be originally
Paper coated with untanned gelatin, may be
formed with the ‘secondary chemical of that proc
packaged in cut sheet or roll form, and if pro
ess, ferro sulphate or its equivalent. Instead, the
tected against moisture, as by being wrapped
gelatin may be plain, but it will be sensitized or
In use, the paper may be wetted from the 15 activated, Just before it is engaged by the orig
inal, by dampening or moistening it with a farm
back. I have discovered, however, that when
sulphate solution. This may be done from the
the wetting pad II is made of a porous stone
block, moisture is evaporated, and such evapo
front or the back. Thereafter, the moisture bal
ration functions to cool the gelatin coating suffi
ance for printing ‘is maintained by the transfer
ciently to enable untanned coatings to be used 20 of moisture through the printing plate from the
at ordinary room temperatures with good results.
back, where the printing plate is in contact with
the wet pad. While it is contemplated to apply
It seems, therefore, that a solution to all prob
lems is offered by the adoption of “back wetting,”
the sensitizing solution from the front, it is, of
by the use of a porous stone block as the wetting
course, obvious that if desirable, it also might
in waxed paper, may be stored.
block or pad, and by the use of untanned-gelatin 25 be applied from the back, but except insofar as
for the coating.
the sensitizing is a moistening step, this is not
particularly important.
For a further understanding of the‘invention
hereof, reference should be had to the appended
The pad H is a porous stone block.
One form
drawing which shows a plate ID in the form
of block, now being sold by Filtros Incorporated
r of a sheet of water absorbent wet strength paper, 30 (formerly General Filtration 00., Inc.) of East
coated on its upper surface with untanned gela
Rochester, New York, under the trade-mark
tin, and disposed upon a moist porous stone block
“Filtros,” and described by that company, in a
or pad II.
A suitable moisture supply for the
bulletin entitled “Filtros Plates," copyright 1944,
pad may be provided, if needed, to maintain the
pad ll continuously moist. >
as “a white rigid, porous, mineral substance, com
posed essentially of silica,” and which “might be
The printing plate I0 is a sheet of wet strength
termed as an ‘arti?cial porous stone’ ” has been
saturating paper, coated on its upper surface with
found satisfactory.
untanned gelatin. It can be manufactured to be
It ‘has been found that maintaining the water
sold dry, in cut sheets or rolls, and is perfectly
balance for printing in the manner herein de
stable under ordinary storing and handling con 40 scribed, by transfer through the printing plate _
ditions. It is economical, easy to make, and easy
from the back to the printing surface, is better
and satisfactory to‘ use.
than any presently known method of maintain
The printing plate hereof may bev and prefer
ing water balance. With gelatin, moisture trans
ably is free of glycerin since it is not required
ferred to it through the paper is molecularlyand
to be hygroscopic, for it is not intended that the - evenly absorbed by the gelatin, with no excess,
water balance for the gelatin surface be main
and without drops of water on the surface, and
tained'by absorption of moisture from‘ the air,
consequently, there is no tendency for the print
but rather it is intended that the water balance
ing ink to spread or emuisify with water.
be maintained by the transfer of moisture from
Further, it has been found that where it is
the pad ll, through the printing plate itself, to 50 attempted to wet the affected printing plate from
the printing surface. Thus the printing plate
the front, great skill, complicated apparatus,
hereof is far less affected by storing and handling
considerable time, frequent interruption of pro‘
conditions than plates containing glycerine in
duction, are required, and even under the best of
which water balance is maintained by the hygro
operating conditions and performances, uneven~
scopic action of the glycerine.
ness of distribution of the moisture occurs, with
The paper functions as a moisture transfer me
the result that the ink spreads, or emulsifies, and
dium, to transfer moisture from the source, name
the unaffected or unhardened or background por
'ly the pad II, to the gelatin surface, and thus
tions of the gelatin swell unevenly around the
chemically a?ected or hardened or image portions
is required to be of a character that retains its
strength during the moisture transfer. For‘this 60 of the gelatin to cause hills and valleys on that
coating, and reproduction is not so satisfactory.
Where there is unevenness of distribution of the
moisture, either no swelling of the unhardened
obtained from the Brown Paper Company, and
gelatin background takes place, or else the swell
known as “No. 201 Aqualized Kraft." Saturat 65 ing of the unaffected or unhardened gelatin is
accompanied" by a similar swelling of the chemi
ing tissue, such as is sold by the Process Manu
purpose, it might well be any well known wet
strength or saturating or absorbent paper. One
paper that has‘ been found suitable is a paper
facturing Company of Chicago, Illinois, has been
found satisfactory. Vegetable parchment papers
cally affected and super?cially hardened gelatin
image. Where the moisture passes through the
have also been found satisfactory. A paper
paper, entering from the back, as in the present
known as L99, of Byron Weston Co., Dalton, 70 case, the undesirable conditions and factors are
Mass, has also been foundsatisfactory.
The paper need not have any capacity for stor-.
eliminated, and, with less difficulty, better repro
duction is obtained.
ing moisture, since only its moisture transfer
If desired, the paper may be supplied with wet- .
characteristic is relied upon to maintain the wa
ting agents, having a tendency to increase the
75 absorption and transfer qualities of the paper.
ter balance.
2,412,889 '
These agents might be applied to the paper dur
ing the manufacture of the paper, or might be
incorporated in the wetting solution.
I claim:
In the art of ‘printing with moisture repelled,
greasy printers’ ink with anon-hygroscopic, ini
tially untanned gelatin surfaced, thin, water ab
where gelatin coatings are thin, as for example, 5 sorbent, wet strength paper printing plate having
a super?cial printing image of hardened gelatin
where the gelatin is in the form of a thin coat
on and surrounded by an unhardened ferrogela
ing, applied to paper, and stored dry. Withsuch
background, the image having been produced
plates, the wetting ~and maintaining of water bal
on the background by surface contact thereof
' Wetting from'the, back is of particular value
ance is a far more delicate operation, and yet
with an original image containing a primary
is far more important, than under conditions 10 chemical which reacts super?cially with the fer
where thick gelatin coatings, frequently renewed,
'rogelatin background to harden the engaged por- _
are used in humidity controlledrooms.
tions thereof to form the selective and super
Using a wet porous stone block as the wetting
?cially hardened image, so that there is unhard
pad is of especial importance, inasmuch as it 15 ened gelatin underlying the image area as well
functions to cool the ‘paper, thus enabling papers
as surrounding it, the step of feeding moisture to
having untanned gelatin coatings to be used at
the plate from the back thereof, so that the mois
ordinary room temperatures, with good results,
- and thus enabling coated papers to be stored and
ture passes through ,the plate to the printing
surface thereof, thus maintaining the water bal
kept inde?nitely, to be useful for reproduction by 20 ance therefor, and also maintaining a constant
the iferrogelatin process. I
Now having described the art of printing here
in disclosed, reference should be had to the claim
which follows:
.‘minimum differential of level of the image and
non-image areas, by applying the paper to and
in contact with a moist porous stone block which
wets and cools the paper. '
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