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Second Part.

SECTION SIXTH.

OF SCULPTURE BY ACIDS.

§ 74. There are secrets in every art, springing from the reflections of men of genius and often from chance, which render easy the execution of works which would necessitate an exceedingly tedious amount of manual labor, without the certainty of accomplishing its end; such are the fillets, the chords, and the rows of glittering beads which are imprinted on metals with a simple mullar, the guilloches which almost form themselves by the perfection of the tools which are used, as well as the beautiful carving upon softened ivory and expanded shell, and the admirable designs upon paper hangings.

The sculpture of Marble without mallet, chisel, or burin, is still more wonderful, and not less easy of execution, for this it is only necessary to know how to utilize acids.

Tables and chimney-pieces of white Marble are sometimes seen decorated with very delicate sculptures, which seem to require an immense labor, and for which it seems impossible that chisels or other ordinary instruments, however delicate, could have been used. The workmen, jealous of their secrets, concealed them in order to increase the price of their work, by causing it to be supposed that much time and pains were necessary to execute these beautiful masterpieces, whereas they were made with the greatest facility.

M. Dufay, having perceived that these works were too delicate to have been made with tools, soon discovered that they had recourse to acids, but experiments were necessary to specify them. Many acids caused the Marble to turn yellow, and were, therefore, inapplicable.

He also experimented upon several varnishes, until he discovered one which was easy to use, which dried readily, and was impenetrable to acids. Such is the course which one is always obliged to follow in the arts, in the simplest researches. The following is his process:

Prepare a varnish by simply pulverizing Spanish sealing-wax, and dissolving it in spirits of wine.

Trace on the white Marble, with a crayon, the design which is to be formed in relief, and cover this delicately with a brush dipped in the varnish; in less than two hours the varnish will be perfectly dry.-Prepare a dissolvent formed of equal parts of spirits of wine, spirits of salt, (hydrochloric acid,) and dissolved vinegar; pour this solution upon the Marble, and it will dissolve those parts which are not covered by the varnish. When the acid has ceased to ferment, and, consequently, will no longer dissolve the Marble, pour it on anew, which continue until the ground is sufficiently grooved.

It should be observed that, when there are delicate lines in the design which should not be grooved so deeply, they should at first be covered with varnish, to prevent the action of the acids upon them; then, when the reliefs have been made, the Marble should be well washed, and the varnish removed from these delicate lines with the point of a pin, then pour on new acid, which will groove it as deeply as desired-care being taken to remove it at the proper time.

It is necessary to observe that, when the acid has acted upon the Marble, it corrodes beneath the varnish, and enlarges the lines in proportion to its depth; care should therefore be taken to draw the lines in relief a little larger than it is desirable to leave them.

When the work is completed, remove the varnish with spirits of wine, and, as the grounds will be very difficult to polish, they may be dotted with ordinary colors diluted with the varnish of gum lac. By coloring these grounds, or the relief which have been thus engraved a beautiful effect will be produced, and one which, if the secret of this art ever be lost, would cause them to be regarded in future ages as chefs-d'ćuvre.

§ 75. M. Osmond, by a similar process, grooves not only Marble, but likewise copper and mother of pearl, and produces with facility effects which are seemingly difficult. For this purpose, he employs bitumen and acids.

The Marble being grooved, he also fills up the cavities in inlaid work with gold, silver, tin, sealing-wax, sulphur, crushed pearl shell reduced to powder called lithoďde, etc.; every design executed in this manner, whatever may be its tenuity or delicacy, becomes indelible and indestructible by air or by the action of time. Any design can thus be engraved in three or four hours to whatever depth is desired, upon an article which could not have been thus decorated in a month's time by the chisel.

These designs can be made either in molding or in relief, without changing or injuring the Marble; every sort of writing, however delicate it may be, can also be thus traced; and the execution is very rapid, whether in groovings inlaid with gold or silver, or in relief which can also be gilded or silvered. It is by these processes that Marble workers execute a large portion of their work in the decoration of monuments with ornaments; and another is more beautiful, or more analogous to the destination of a tomb, than these lapidary incrustations which Time cannot destroy or even impair, until after repeated whettings of his schythe.

Do you wish to inlay with leaves of mother of pearl? You no longer have need of the chisel to cut them; you make the grooves upon the Marble, and, with the aid of the needle, in a few minutes they are cut and the designs executed, or whatever nature they may be.

We might here repeat all that we said at the close of the article upon the veneering of Marble. There is some analogy between these two processes, both of which tend to increase the use of Marble to a great extent.

Without wishing to deprive any of the modern inventors of their deserts, we will conclude by quoting from a very interesting article found in the Dictionaire Encyclopedique, published in 1785. In volume fourth, page 404, the following paragraph may be found:

"Some have succeeded in sculpturing Marble in very delicate designs by the aid of an acidulous liquor, which is formed by a mixture of spirits of salts and distilled vinegar. Before the corrosion of the acids, the parts to be preserved in relief are covered with a varnish of gum lac dissolved in spirits of wine, or simply of Spanish sealing-wax dissolved in the same acid. The acid does not affect the varnish."

It would be difficult to say more in fewer works-What do inventors deserve, when proofs are thus placed before their eyes that all their pretended discoveries, with the exception of natural philosophy and chemistry, which have made great progress, are but reproductions of what was formerly practiced? In architecture, in joining, in locksmithry, in Marble working, in painting, in sculpture, in gilding, there is nothing valuable known to us, but what was used by the ancients, even in the Renaissance. If we have, in respect to sciences, the right to call ourselves glorious, in relation to the arts, it is our duty to be modes.



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