A METHOD OF MANUFACTURING VERDIGRIS OF THE SAME QUALITY AS IS KNOWN IN COMMERCE BY THE NAME OF FRENCH VERDIGRIS
Year: 1813

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME, I, GODFREY
KNELLER, of Croydon, in the County of Surrey, Chemist, send greeting.
WHEREAS His most Excellent Majesty King George the Third did, by
His Letters Patent under the Great Seal of the United Kingdom of Great
Britain and Ireland, bearing date at Westminster, the Eleventh day of July,
in the fifty-third year of His reign, give and grant unto me, the said William
Godfrey Kneller, His especial licence that I, the said William Godfrey
Kneller, during the term of years therein mentioned, should and lawfully
might make, use, exercise, and vend, within England, Wales, and the Town
of Berwick-upon-Tweed, my Invention of "A METHOD OF MANUFACTURING
VERDIGRIS OF THE SAME QUALITY AS IS KNOWN IN COMMERCE BY THE NAME OF
FRENCH VERDIGRIS;" in which said Letters Patent there is contained a pro-
viso obliging me, the said William Godfrey Kneller, by an instrument in
writing under my hand and seal, to cause a particular description of my
said Invention, and in what manner the same is to be performed, to be
inrolled in His Majesty's High Court of Chancery within two calendar
months after the date of the said recited Letters Patent, as in and by the
same, relation being thereunto had, will more fully and at large appear.
NOW KNOW YE, that I, the said William Godfrey Kneller, in com-
pliance with the said proviso, do hereby declare that, in specifying the means
I adopt for the manufacture of verdigris, it may be necessary to state the
materials employed for that purpose in France, in order that it may be seen that

page_text: the substitute I employ is fully adequate to its object, as well as a variety of
other resources, the produce of this country, equally applicable to the production
of what is designated the French verdigris.
The materials employed in France are sheets of copper of small dimensions
and the refuse of the grape after the extraction of their juice, known in France,
and particularly at Montpelier, by the name of rague. Without describing
the further means pursued; I shall confine myself by-observing-that the grape is
not the only vegetable substance which may be employed to advantage, but all
substances indiscriminately, as long as they possess those natural fermentative
properties in which they can be made to pass into the state of the acetic acid;
and fruits and most vegetables possess these properties of producing an acetic
acid, and various modes may be adopted to obtain it, according to the views
of the manufacturer. We may also oxydize copper by other known processes.
Many animal and saline substances corrodes copper; dipping copper sheets in
certain acid solutions and afterwards exposing them to the air, subjecting
them to the vapours of the acetic, oxymuriate, nitrate, and muriatic acids, pro-
duce oxydation; but all these do not produce that species of verdigris known
in common by the name of French verdigris, and nothing alone is able to
produce it by an intimate combination of the acetic acid with copper; for
whatever substance is employed it must be colourless of partake of a sufficient
quantity of the acetic liquid, without which it will dry up before it has time
to exert its power on the copper. I take copper sheets from twelve to fifteen
inches diameter, each sheet weighing about one pound and a half, and having
prepared them by dipping them in a solution of verdigris, I proceed as follows:
I have already observed, any substance capable of holding a certain portion
of acids answers these ends, Ist, by giving a body. for the copper to rest upon,
2ndly, by its acid quality exerting its influence on the copper. I then take
the following artificial mode of substituting the grape-I take sponge, and
having cut them into small pieces so as to resemble the size of the grape,
wet them with a sufficient quantity of the acetic acid, which I obtain from the
grains of beer after the first brewing, for the sake of economy; but I would
wish to be understood that any other means by which the acetic acid can be
obtained will answer the same purposes. After having wetted a sufficient
quantity of these pieces of sponge, which ought to be performed in a large
stone pan, the subsequent steps are as follows:-The copper sheets are then
brought near the pan, and a sufficient quantity of these wetted materials are
placed stratum super stratum, so that they may bear équal in all their parts,
care being taken the sponge between the sheets are not too close, as that would
prevent the action of the air passing between them, which so much facilitates
I

page_text: the oxydation. From twelve to fifteen sheets are placed on each other, and put
into a stone pan, and covered with a slight canvas or straw covering, or they
may be placed on the ground floor, or in any other situation which may suit
the convenience of the manufacturer, as much depends upon the temperature
of the place, which is only known by constant habit, placed in an underground
apartment, there to remain 5 or 6-days, when a sufficient quantity will have
generated. It may be seen that the quick operations possesses advantages
superior to those where the grape, &c. are obtained. The sponge is then
taken from the sheets, and the verdigris may be taken off immediately if suffi-
ciently abundant; if not, it may be subjected to a similar treatment. The
sponge, after once or twice using, will be found to contain a large portion of
acetate, of copper, which, if subjected to a continual using, would become
saturated when a fresh portion of acid was used, and would have no power to
act on the copper; it is therefore only necessary to wash in a stream these
spongy materials, and afterwards, if necessary, immerse them in a tub of
water weakly acidulated with the sulphuric acid, wash them again in fresh
water, and dry and use them as before. For many centuries the grape has
been exclusively in use in the, manufacture of verdigris as the only material
that could most conveniently be obtained, and which has always appeared to
possess those combined qualities which give it that peculiar preeminence, and
which has long been considered, as the only substance that could be employed
successfully; and it must be, admitted, from the facility the grape ever obtained
in wine countries, their size, the ease in which they are (by fermentation) con-
verted in a proper state for dissolving copper, give it the advantage over every
other, vegetable substance. The manufacture of verdigis would admit, in this
case, of very considerable improvement; and it has always been a matter of
surprise that the manufacture of this article, and of such extensive use in the
arts, should not have induced individuals to form establishments of this descrip-
tion; but the cause is obvious, for without other methods are discovered of
substituting the grape, it never could be conducted. In the first place, a manu-
factory established in wine countries could, for the most part, only employ
three or four months in the year; nor could an individual wrest from the
hands of a large population a species of manufacture which has for ages past
been a very considerable source of industry. From the before-mentioned
circumstances it is easily conceived and clearly established that the manufac-
ture of verdigris is solely confined to the husks or stalks of the grape, as is
generally described and uniforinly written upon; nor is the grape of any
further utility than merely to act as a substance that can only be considered
as imperfectly containing a natural moisture, from the fermentation that takes

page_text: place from a large mass of these materials, as well as possessing a degree of
hardness sufficient for a small sheet of copper to rest its whole weight upon,
without suffering too great a degree of compression; for was the grape used
merely in its ripened state, no effect would be produced, a fact so clear to the
most unscientific observer, that it is only to shew that these fermented mate-
rials pass into the state of vinegar, whether we use the vinegar by itself, or
combining it with a body containing it, the result is always the same with
respect to the production of the article; but as it may be desirable to obtain
it in a greater or less degree of purity, it is an object with the cautious manu-
facturer to select the most perfect materials for that purpose. The grape,
therefore, cannot be considered the most proper for that purpose, but superior
to any other vegetable production, a proof of which is its long and invariable
preference given to it in all countries where the grape is cultivated, and where
the making of verdigris is a domestic amusement, confined to a few months in
the year. The grape, therefore, if not properly treated, becomes mouldy, and
rots if gathered in a wet season, or, not sufficiently ripe, counteracts the views
of the manufacturer; from these and other minute causes, render it frequently
precarious, and very often bring with it a dirty or foreign body, which deprives
it of that beauty which it ought to possess if used as a colour; and we may
frequently see it intersected with stalks, stones, and pieces of 'substances, which
proves troublesome to the artist, although of no consequence with respect to
its quality. The sponge cut in the way I have described comprehends all
these combined qualities of the grape, with this peculiar advantage over that
material it presents to the surface of the copper a clear and pure acid; it is
susceptible of partaking any quantity of acid it may be desirable to it; it is
not too hard a body to press its acid juice from it, nor too soft to be flattened
by the pressure of the sheet, but preserves an uniformi elasticity, and evidently
appears, from these combined advantages, to possess exclusively the necessity
of the use of the grape. This being the general outline of all that may be
particularly deserving of notice, I must merely observe, there are a few
miniutias and trifling manipulations which it would be impossible to describe,
as practice can only be a guide to the manufacturer. The verdigris, when
made, is capable of crystilization by dissolving it in distilled vinegar, and
pursuing the same means as in the French.
In witness whereof, I, the said William Godfrey Kneller, have hereunto
set my hand and seal, this Tenth day of September, in the year of
our Lord One thousand eight hundred and thirteen.
W. G. KNELLER. (L.S.)

page_text: AND BE IT REMEMBERED, that on the Tenth day of September, in
the year of our Lord 1813, the aforesaid William Godfrey Kneller came
before our said Lord the King in His Chancery, and acknowledged the
Specification aforesaid, and all and every thing therein contained and speci-
fied, in form above written. And also the Specification aforesaid was stampt
according to the tenor of the Statute made for that purpose.
Inrolled the Tenth day of September, in the year of our Lord One
thousand eight hundred and thirteen.