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Second Part.

SECTION FOURTH.

OF THE VENEERING OF MARBLE.

VENEERING UPON WOOD AND STONE

69. The plating of silver, the veneering of costly woods upon common ones, and that of Marble upon walls, might have naturally suggested the idea of the veneering of Marble upon wood for pedestals of clocks, little articles of toilet furniture, or even for centre and all other ornamental tables.

M. Mudesse claims to have found a certain method of effecting this object, without the obstacle which the constant warping of the wood opposes to the preservation of the Marble, which is often broken by this expansion.

During several years, the use of Marble upon stone has greatly increased, despite the inconvenience of the enormous weight of the articles manufactured of the plated Marble, which has also caused their transportation to be very expensive.

Marble workers have sought to obviate these difficulties as much as possible, for ornamental clocks in particular, by hollowing out the interior. But this method, by leaving only a slight thickness of stone, compromises the solidity of the plated articles, and exposes them to many risks in transportation.

M. Mudesse has devoted much time to experiments in order to remove these obstacles, which have resulted in the discovery of a method by which veneering upon wood may be substituted for that on stone.

This new process, which is safe and solid in comparison with the old, offers every possible advantage to dealers in Marble.

The principal difficulty has been in veneering the Marble firmly upon the wood without danger of its breaking. The removal of this difficulty would procure the following advantages:

Firstly. The lightness of the plated articles, and their consequent facility for transportation, with the great reduction of price which would result in the diminution of the weight.

Secondly. The simplification of labor-as the wood could be easily hollowed out as much as deemed proper without danger of its breaking, which often happens to the stone.

Thirdly. The absence of the oxydation of the pieces of iron and steel composing the movement of a clock; an oxydation which is inevitably produced by the dampness communicated to them by the stone, and which, when dry, shells off and scatters its dust in the pivots, which stops the working of the movement, and proves an incessant cause of repairs.

"Thus," says M. Mudesse, "veneering upon wood is preferable, in every respect, to that on stone."

M. Mudesse has also made many experiments in the plating of Marble upon different metals, but has found that none possessed the same advantages as wood, in respect to resistance, solidity, and lightness.

The difficulty to be obviated was in the manner of veneering the Marble upon the wood.

For this purpose, as Marble, particularly the black, would break by heating it in the usual manner, M. Mudesse places the slabs of Marble in a cauldron, tightly closed, in which he lets them boil. He then takes them from the cauldron, and after this preliminary operation, he can, without risk, subject that Marble to the heat of the fire to receive a mastic of tar. The wood having been first prepared in a similar manner, he presses the Marble, coated with the mastic, upon the wood, and a perfect cohesion is effected.

The mixture of glue with tar, is found an improvement in effecting this veneering.

70. We said above that M. Mudesse had unsuccessfully endeavored to plate Marble upon various metals: these possessing a smooth and polished surface, the substance which should fasten them to the Marble, could not incorporate itself with them intimately enough to join both and render them inseparable.

To resolve this problem, it was necessary to interpose between the metal and the Marble, a third body, which should force them to perfectly adhere; this he effected by the use of sand paper.

The cases of ornamental clocks are hollow, for the movement of the pendulum and other works. This hollowing cannot be effected on stone without detriment to its solidity.

But when wood is used, a frame is made of it, varying in form to suit the taste of the artisan, and the exterior parts upon which the Marble is to be veneered.

The following process is that which is employed in the plating of Marble upon zinc:

Take a plate of zinc of about the tenth part of an inch in thickness; make a frame of this of the form of one of the parts which compose the case of the clock, or whatever other article may be wished; upon this form glue the sand paper, leaving the rough side outermost, and upon this rough side apply the Marble, having first prepared it by heating in a water bath, and placing between the Marble and the sand paper a coating of mastic of tar.

By this means, so perfect an adhesion between the Marble and the zinc is effected, that the Marble could be easier broken than removed.

In case of need, coarse emery paper produces equally as good effects. The cohesion of the Marble upon the metal by the interposition of powdered glass or emery by means of glue, is not as perfect; the paper adheres better to the metal.

The inventor has given the preference to zinc over other metals, because it possesses both resistance and cheapness, and causes no other expense in the manufacture than that of cutting up to form the model.

Tin possesses neither the same resistance or the same cheapness; sheet iron is dearer; cast iron is too heavy; copper is expensive; while, by the application of Marble upon zinc clocks or other articles can be manufactured and put in market at the same price as those veneered upon wood.

Taught by experience, M. Mudesse has joined to the processes of which we have spoken other means of execution, which we shall mention.

We have said that, in fastening the Marble to the metallic plating, the tar which is used in the application of Marble to stone will not be sufficient; for the metallic plate and the Marble do not possess sufficient roughness to absorb and connect themselves with the glue so closely, but that a slight shock will disjoin and separate them.

It was necessary, then, to find an intermediate mordant to effect the solid and inseparable adhesion of Marble to metals, and to replace the sand paper effectually.

When, in making the case of a clock for instance, it is desirable to apply Marble to a plate of zinc

or any other metal, the parts must first be heated in a water bath, or over a furnace prepared for this purpose, and then, by means of a sieve, sprinkled with one of the following mordants:

Crushed glass, grains of emery of all sizes, copper filings, castings of any metal, finely rasped lead, any kind of powdered stone, such as sandstone, Marble, granite, pumice-stone, etc., even caoutchouc can be used.

When the sheet of metal and that of the Marble have thus received a sufficient mordant, they are joined with a coating of tar, which fastens together the roughness of these two substances, and forms a solid and inseparable whole.

The inventor, believing he had attained the highest degree of perfection in the application of his methods to the plating of Marble upon wood and metals, gives this abstract in a statement given to obtain a patent, in October, 1841.

"In the substitution of wood and every species of metal for stone, upon which, formerly, the plating of Marble was made, this problem has been resolved:

The production of perfect cohesion between two smooth surfaces.

This difficulty did not exit in the plating of Marble upon stone, because this being by nature grainy and spongy, it gave every facility to the clinging of the mastic, and the adhesion could be effected by the simple interposition of the mastic between the Marble and the stone.

But the same result could not be obtained between two smooth surfaces, as between Marble and metal."

"After numerous experiments to find a mastic, the grained composition of which might replace the roughness of the stone, I was convinced," says M. Mudesse, "that whatever might be the composition of this mastic, its sole interposition between the Marble and the metal could not produce an adhesion sufficient to resist the shocks and concussions attendant upon the transportation and working of these pieces.

I finally succeeded in discovering a process, which consists in establishing an artificial mordant upon the plates of zinc, or other metal, and that of the Marble, and then causing the adhesion of these two surfaces thus rendered grainy, by the interposition of common mastic, or tar."

The artificial mordant is fastened to the surfaces by means of paste, or other glue.

These methods are not only applicable to the cases of clocks, but also to frame-works of every kind, and to all articles of ornament or luxury.

71. It can be easily supposed that the above rules will apply to anything which is susceptible of being veneered with Marble, and M. Adin has used them for dressing-cases, work-boxes, and other articles.-The following statement was given by him on the twenty-second of March, 1842, of what he calls his invention:

"The Marble is first sawed to the desired thickness, and to the form required for the dressing-case or the work box to which it is to be applied. When the pieces of Marble are thus sawed, the wood is prepared, (usually white wood, oak or fir) by cutting it in the same manner, but a very little smaller than the Marble which is to cover it. This wood is interlined with a shaving of beech wood, in order to prevent warping. This beech wood lining is only placed on the side which is to receive the plating of Marble; each piece of Marble is then applied to the corresponding piece of wood, and the adhesion is effected by means of glue or other mastic. When the Marble has thus been applied, the opposite side of the wood is thinly lined with rosewood or mahogany, in such a manner that this lining forms the inside of the box or dressing-case, which is thus prepared for receiving the necessary divisions and compartments. The four parts are then dove-tailed together, and the top and bottom parts fastened flatwise on the four sides with glue or mastic.

The box being thus finished, the outside is pumiced and polished, and any applications of gilding can be made.

The chief point of this invention consists in the idea, realized by me for the first time, of the application of Marble to the manufacture of dressing-cases, work-boxes, and articles of this nature, which have previously been made only of wood, cardboard, and leather."

There may be some little obscurity in this description, but it will be perfectly understood by all readers who have any knowledge of the art, and they, probably, are the only ones whose attention will be attracted by it. This veneering is so much in use, and so valued, that we deem it unnecessary to enter into farther details respecting this new art, which is of so much importance, particularly in a commercial point of view.



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