The Sun.
London, England, 1858-11-29 00:00:00

SOCIETY OF ARTS.

The usual weekly meeting. was held on Wednes-
day evening under the presidency of Mr. George T.
Doo R.A.
Mr. F. JOUBERT read a paper " On a Method of
rendering engraved copperplate capable of pro-
ducing a greatly increased number of impressions."
The author began by giving a brief account of the
discovery of th e art of obtaining impressions on paper
from engraved plates, which is supposed to have
taken place about the year 1452, the art of pro-
ducing ornamental designs on metal and other sub-
stances having been practised from very early times.
The comparatively small number of impressions
which can be taken from a copperplate necessitated
the employment of the harder metal—steel. The
discovery of electrotyping led to the multiplication
of engravings on copper by this process ; but it was
found. that in consequence of the softness of the
metal deposited the plates would yield but a limited
number of good impressions. Under these circum-
stances it had become a desideratum to harden, if
possible, the surface of a copperplate so as to protect
it from wear while printing. The invention ,which the
author then described, consists in covering the print-
ing surfaces, whether intaglio or relief, and whether
of copper or other soft metal, with a very thin and
uniform coating of iron,.by the action of the gal-
vanic battery. The operation takes place in this
way :—By placing at the positive pole a plate or
sheet of iron, and immersing it in a proper iron
solution, the metal will be dissolved under the ac-
tion of the battery, and if a copper-plate be placed
at the opposite pole, and likewise immersed, the
solution being properly saturated, a deposit of iron,
bright and perfectly smooth, is thrown upon it. It
should be remarked that the coating of iron admits
of being removed from a printing surface of copper
without injury to the original plate; hence the
original plate may, after being coated and used for
some time, have the worn co ting removed, and
then be recovered with an iron coating as often as
may be required ; and if care is taken to remove the
coating of iron before it has been worn away, the
engraved copper or other plate maybe made to print
a vast number 'of impressions and yet remain in the
original state it was in when it left the hands of the
engraver, or was otherwise first produced. The only
limit appears to be in the gradual change which
takes place in the body of the printing surface by
the compresSion to which it is subjected in the
process of printing. The author states that he has
found that an electroplate, 40 by 22 inches, coated
with iron has yielded 2,000 impressions, without
its being necessary to remove and renew the iron
coating, there 'being no perceptible difference be-
tween the first and last impressions. He is of
opinion, that this process will be found extremely
valuable for electrotype and photogalvanic plates,
since they can be so protected as to acquire the
durability of steel, and even more so, for a steel
plate will only require repairing from time to
time, whereas these will only require recoating
whenever it is found necessary. By these means
the author states that one electro copper-plate
was made to yield more than 12,000 impressions,
and was found quite unimpaired when examined
minutely.