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Fourth Part.

SECTION FOURTH.

OF ARTIFICIAL MARBLES.

120. Should we commend the efforts which are made to give us counterfeit productions, or ought we to oppose all such products as encouraging fraud, and injuring honorable artists? This is a delicate question when asked respecting jewelry, cloths, furniture, and many other articles. It also affects Marble working, for it is very evident that the artificial Marbles injure the Marble workers, as much as the manufacture of paste jewels injures the diamond merchants.

Notwithstanding this, if the artificial Marble should become a principal article of commerce, the Marble workers would be better able than any speculators to manufacture Marble, and convert it into a branch of their art. For this reason, we deem it advisable to occupy some time with these artificial Marbles, the success of which is somewhat problematical.

The Marble composed by man has long been known by the name of stucco. Will the artificial Marble be preferable to this? This is doubtful. Will it be more valuable than the plated marble? Experience must demonstrate it. While waiting for the decision, we will examine the different methods which have been proposed in the course of a few years, and view their respective advantages.

121. In 1823, the first patent of invention was taken out for fifteen years, by Madame Dutillet, for processes relating to the formation of artificial Marble. The following statement was made by her of the discovery which she claimed to have made:

"The artificial Marble which is composed by the aid of calcareous substances, has all the ductility, polish, frigidity, etc., of the natural Marble.

"It can be used for basins, floorings of bath-rooms, vestibules, etc.; in short, in all places which are exposed to drought or humidity. It can also be employed in the construction of churches and other public buildings which dampness defaces, and frescoes can be applied to it with great facility, as the colors do not fade, and retain all their brilliancy."

COMPOSITION OF ARTIFICAL MARBLE.

122. "To one hundred and ten pounds avoirdupois of pulverized Marble which has been sifted, add thirty-nine pounds of crushed and sifted bricks, and twenty-two pounds of glass, also pounded and sifted. Add to this five times the quantity of hydraulic lime, and carefully stir it with water to form a paste susceptible of being worked with the trowel."

When a smooth layer has been applied to the surface to be coated, draw with a brush the veins and the color of the Marble which you wish to imitation. Then put one pound of Venice talc in a linen cloth, thus forming a packet, and sprinkle the surface that has just been coated and painted. After this gloss it, by rubbing it with the trowel, until the polish and frigidity shall be obtained.

"You can give to the paste the color which is to be communicated to the ground of the Marble. For this, add the color at the moment of mixing the paste, taking care only to employ mineral colors. Vegetable colors must never be used.

"A powder may be made of crushed porcelain, silex, sandstone, or other hard stones, or even with clay, (taking care to extract all vegetable matter,) which will amalgamate well with the composition of artificial Marble."

Madame Dutillet seems to have been successful, as she sold her patent, and the purchaser took out, in 1824, a patent of improvement, in which the following modifications are found:

123. The materials employed, as has been said before, must be freed from all vegetable and animal matter which they may contain, that they may form an indestructible composition. After the substances have been pulverized, they are baked long enough to destroy any vegetable or animal parts, and this powder is mixed with thick lime, or hydraulic lime, according to the dampness or nitrifying of the localities. All the colors employed are also purified by fire.

Before applying the material upon the stone, the surface of it should be washed with water, and scraped if necessary; after which, any vegetable matter which may exist upon the stone is destroyed by the means of acids, applied with a brush of amianthus, or mountain flax. Ornaments, and even figures, may be painted by the aid of an economical process, consisting in the use of plates of copper, or of waxed cartoons, which are cut out to form the necessary holes.

When the coatings are finished, and the painting is applied to the Marble or the ornaments, it is polished in the ordinary matter. But, to obtain a greater brilliancy, a composition of the essence of turpentine and white wax melted by the fire, may be used.

This composition is laid upon the surface with brush, and then rubbed with a skin; and in this way, the essence having consumed all foreign substances which may have lodged on the surface, the wax unites with the material by the action of the lime, and a most beautiful polish is attained.

This new material can also be molded into all kinds of ornaments in relief, busts, statues, chimney-pieces, etc.

124. The matter did not rest here. On the 28th of January, 1825, the patentees of Madame Datillet took out a new patent of addition, in which it is stated that calcareous matters, oyster shells, marl, talc, should be calcined in a crucible or oven, and then reduced to powder, to which is added an equal part of hydraulic lime, slaked by immersion or otherwise.-The whole should be passed through a silken sieve; and when the composition is to be molded, it should be tempered like plaster. The inventor adds that the polish is obtained by means of Venice talc, and that the coloring can also be laid on the paste.

125. Another process was described in June, 1840, by M. Chenard, of Paris, for which he took out a patent for five years. We will let him speak on his own behalf:

  1. I make a preparation, composed of good linseed oil reduced and the essence of turpentine, which I mix with litharge and umber when the oil is of an inferior quality.

  2. I spread this preparation upon the surface to be marbled, either with a brush or with a metal scraper.

  3. I then dry the article thus coated.

  4. I give it a second coat of the said preparation, and even a third if the body which I wish to Marble is not sufficiently covered by the first and second; a thing which may be easily known if the surface of the body can yet be seen in spite of the coatings already applied. The true ground of the Marble is placed upon these preparatory coatings, the color of which it is to be formed being mixed with it.

  5. I have a trough filled with water, and larger than the object to be marbled, on which I throw the color ground up with the varnish of linseed oil, weaker than that used in the preparation, to which the essence of turpentine and a little table oil is added.

  6. With the breath and a small stick, I arrange this thick substance upon the water in such a manner as to give to the foreign body which I afterwards dip in it, all the different shades, designs, and peculiarities which are found in nature.

  7. I then dip the foreign body, coated with the first preparation, and well dried, in the trough, and draw it forth again ornamented with veins and shades, naturally arranged, which the most skillful painter could not produce, since this is a simple effect of nature, while his would be but an incorrect copy.

  8. I then give it a coat of fine varnish, or two if necessary-it being understood that it should be thoroughly dried after each operation, before commencing the following one.

  9. Finally, to obtain the smoothness and appearance of genuine Marble, I give a polishing stroke to the whole, which neither impairs the brilliancy of the colors, or affects the surface to which the composition has been applied."

126. Three years later, M. Riotet made farther discoveries in this art. His idea was to veneer with artificial Marble as a substitute for rosewood, mahogany, and citron wood, both for the inside of boxes, dressing and night tables, and the top of various articles of furniture, besides which, he composed an artificial mosaic, which he calls Parisian mosaic. He makes the following statement of a process which he claims to be both simple and economical:

"Substitute for slabs of natural Marble, those of the artificial Marble, of equal solidity and somewhat less weight. Increase the beauty of the article manufactured by the variety of colors which this artificial Marble may be made to assume, and, above all, by the application of a genuine mosaic, designed with all the art which is used in the composition of mosaics upon stone. this is the object which I have had in view, and which I have finally been permitted to attain.

"The composition which I use for the manufacture of artificial Marble designed for veneering, and for the fabrication of the mosaic, is a mixture. The two substances, when united, acquire a great solidity; the gum arabic diminishes the excessive draught of the gelatine during the drying process and the cabinet work; in a word, by the union of these two substances, a complete substitute for Marble is obtained in all its applications to veneering, and also to the fabrication of articles of furniture, dressing-cases, ornamental clocks, etc."

COMPOSITION OF THE SLABS OF MARBLE.

Weight equal quantities of gum arabic and gelatine, hydrate each separately, only softening the gelatine enough to render it entirely flexible.

Place the gum arabic entirely in solution in the smallest possible quantity of water; when it is dissolved, strain it through a coarse cloth in order to separate all foreign substances.

When both are thus prepared, melt the gelatine in a porcelain vessel placed in a water-bath, leave it to boil until a species of skin produced by the scum which the gelatine always contains is formed upon the surface of the liquid.

During the boiling of the gelatine, prepare the different colors which are to shade and to form the veins and coloring of the Marble.

These colors should be fine, and ground in water; those most used are silver leaf, white lead, chrome yellow, carmine lake, English green, and all the colors which are generally found in commerce-the gum and gelatine receiving them all.

These different colors are ground in water, and placed separately in vessels designed for this purpose.

PREPARATION FOR CASTING THE SLABS.

127. The slabs of Marble are cast upon a polished Marble of an inch and a half in thickness and about thirty-five inches square, which is placed upon a strong wooden frame resembling a table; care being taken to place this Marble upon a perfect level, so that the material in running, may be of an equal thickness.

Spread a little suet over the marble to prevent the adhesion of the material.

The Marble being thus prepared, place a wooden frame of about one-third of an inch in thickness upon it, to receive and retain the material when it is cast.

As regards the size of this frame, supposing that slabs of twenty-five inches square are wished, it will only be necessary to cast them twenty-one or two inches, for, in the succeeding operation of tanning, the slabs will expand three or four inches which will give them the desired size.

As so slender a frame will not rest well upon the Marble, it should be supported by thick wooden wedges, clasped with a cabinet maker's hand screw.

CASTING.

128. When a slab of Marble of four colors, yellow, green, black and white, is to be made; after the gelatine is boiled and the gum is well dissolved, take a sufficient quantity of each of these colors to color a quart in the whole of the gum and gelatine used in the operation, place these separated in small earthen pans, take the solution of gum, and pour an equal quantity in each of these pans in order to dilute the colors, (care being taken that every particle of color is diluted), then take the gelatine, which must be strained through a cloth to make it clear, and pour the same quantity into the pans in which the colors have been diluted with the gum. Stir the whole well with a brush, that the mass may be well mixed and the color uniformly distributed through the liquid, let it rest for a few moments in order to give the bubbles of air which have formed during the agitation, time to come to the surface; then remove these with a skimmer until the liquid is entirely free from them: This is very important in obtaining smooth slabs of Marble. When this has been done, pour these four different colors into a vessel especially designed for this purpose, and which may be described as resembling four funnels joined together, the tubes resting against each other.

It can be easily understood that, on leaving the orifice of each of these tubes, the colors mix and unite in spreading over the Marble, thus forming the rich and varied shades of the finest Marbles, lapis, porphyry, etc.

This may be done in a different manner when imitations of ribboned stones are wished. For this, pour each of the colors separately upon the Marble, taking care to spread them in small pools over the whole surface; then, with a wooden spatula, form the ribboned shades which are wished, by lightly moving the mixture.

In both these operations, the last in particular, it is impossible to prevent the formation of bubbles of air in the agitation. The best method of destroying them is, after the material has congealed, to take a fine wet sponge, and burst these bubbles by gently striking them. When this has been done, take a thin plate of sheet iron about twelve inches square, with the edges raised in such a manner as to hold burning coals; pass this over the surface, as near to it as possible without touching the material.

This intense heat will melt the surface of the slab, and close the vacuum formed by the bubbles of air.

TANNAGE OF THE SLABS OF MARBLE.

129. The most important operation in the composition of artificial Marbles is that of tannage, without which it would be impossible for the cabinet maker to scrape and polish the material. It would be too malleable for any use.

It is very evident that a soluble matter like the gelatine and gum would melt by the heat caused by the scraper and cling to it in particles, in which case instead of smoothing them, the tool would produce a contrary effect.

The result of this tannage is, to render the gum and gelatine insoluble, even in boiling water, and to transform it into a substance resembling horn. In this state, indeed, the material is scraped and polished in the same manner as horn.

130. For this operation, a tank lined with lead of about twenty-seven inches in length, and fifty in breadth is required, as room is necessary to change the place of the slabs which are placed in it.

This tank is designed for the reception of the liquid possessing the property of tanning.

This liquid is composed of one part of the sulphate of alumina based on potash, and twenty parts of water.

Pour this liquid into the tank, and place the slabs in it, leaving them until their entire thickness is thoroughly penetrated by the liquid. To be sure of this, by cutting off a small corner it can be seen how far it has penetrated, that part which has absorbed the liquid will present a shining appearance, while that which is not penetrated will be of a dull color.

When the liquid has entirely penetrated the slabs, draw them from the tank, wash them in clear water and wipe them carefully; then fix them on strong wooden frames by the aid of very strong plaits of threat coated with glue. Glue a light cloth upon the frame in such a manner as to sustain the weight of the slabs during the drying process, and then expose them to the open air upon benches, leaving space enough between them to permit the air to circulate freely.

When the drying is complete, moisten the cloth and plaits that hold the slab in the frame, carefully, in order to avoid breaking the slabs.

FABRICATION OF MOSAICS.

131. This composition of gum and gelatine can not only be made to assume the form and appearance of Marble, but with small fillets of various colors, ornamental work, such as mosaic, may also be obtained.

The different experiments which I have made convince me that one could, by my process, attain the perfection of the ancient mosaics; this would be of great importance to many of the arts, such as jewelry, bronze, and cabinet work in particular, in which nothing of the kind has ever been known.

It is easy to imagine the effect which a mosaic of flowers or any other design would produce upon an article of furniture.

Until the present time, mosaic work has kept many amateurs at a distance by its high price. By my process it can be easily used in various arts, since a diminution of at least four-fifths of its price is procured.

To make a boquet of flowers, or a rose, for instance, the design must first be executed in water colors by a skillful artist. This design is then divided into squares like the patterns for needle-work. By this means this rose will be divided into at least a thousand little squares containing all the shades. These squares traced on the design show the number of fillets necessary to form the rose, these being shaded precisely like the design.

By joining these square fillets together, the model will be exactly reproduced. For the fabrication of these fillets, slabs of plain colors should be made by the process which I have just described for the Marble.

132. In executing a design, it is important to study carefully the shades of each flower. It is evident that at least six shades are needed to form the rose; namely, white, which forms the light, light rose, rose, deep rose, red, and dark red which gives the shade.

Proceed in the same manner for all other flowers of different colors.

When the different colored slabs which are needed in the composition of the mosaic are dry, remove them from the frames in the manner which I have just described for the Marble. Soak them in the trough in pure water for about a quarter of an hour until they are flexible, then place the slab thus moistened between two blocks of wood so that the surface may be entirely covered, leave it thus for twelve hours in order to give the water time to penetrate it thoroughly and then proceed to the cutting of the fillets.

For this operation in which the fillets should all be of the same size, this regularity can only be obtained by a fillet-cutter, formed with precision.

GLUEING OF THE FILLETS TO FORM THE DESIGN.

133. When the design is to be formed by the collection of the fillets, the design which is divided into squares must be used. We will suppose this design to be divided in one direction in fifty lines, which are themselves crossed by fifty others, thus giving a total of two thousand five hundred fillets; these fillets should be glued in straight lines of fifty fillets each, calculating the shades which should compose them from the pattern, with the aid of a tool designed to keep the fillets in place while they are being glued. When the rows have been thus glued and carefully numbered, they should be placed upon each other, according to their numbers, in such a manner as to form a block, which should be surrounded with strong paper or thin wood in order that the fillets may not be unglued in cutting this block in slices.

UNCHANGEABLE CHINESE PAINTINGS.

134. These paintings are executed upon paper, and covered over with a very transparent and well tanned sheet of gum and gelatine, prepared by the same process as the slabs of artificial Marble.

When the drying process is complete, scrape one side of the sheet with a cabinet maker's scraper until it is perfectly smooth. Then detach it from the frame and cut it in the shape and size of the articles which it is to cover.

Use gum arabic dissolved in water for the application of the designs; spread a coating of it over the transparent sheet, lay on the design and glue it by means of a strong pressure under a press.

One important precaution should be taken in order that the glue used by the cabinet maker in veneering, may not penetrate through the paper; namely, to spread a coating of strong glue upon the side which is to be veneered, afterwards sprinkling it with well dried Bougival white by means of a silken sieve. This operation should be repeated twice at least; it is then left to dry, and afterwards inlaid in veneerings and cuttings.

135. The provinces also endeavored in 1842, to produce artificial Marbles. M. Mondon, of Vienna, claimed to have found a material suitable for this purpose in the department of Charente. He calls it gypseous alabaster-a soft substance which must first be hardened in the following manner:

Put the pieces to be worked in a furnace, placed upon sheets of zinc, which are formed in such a manner as to hold water. This furnace should be built so that the pieces may not come in contact with the fire; leave them for an hour exposed to the action of a heat not strong enough to bake them, for this substance being gypseous, they would thus be reduced to baked plaster and would have no solidity. When the material is well heated and freed from all humidity, the pieces should be sprinkled with tepid water in which a quantity of alum, proportioned to the number of pieces, has been dissolved; they may even be soaked in it for a moment. The tepid water which has not been absorbed by the material is then removed, and cold water is placed in them.

By this means they attain such a degree of hardness, that the final polish can only be given after successively using the sand-stone, pumice-stone, and shave-grass; care being taken to constantly sprinkle the piece, as it will otherwise be impossible to polish it; lastly, a little white wax is spread upon a linen cloth, and, by rubbing with this, the finest white Marble is obtained.

The colored Marbles are made in the same manner, with the exception of the dissolution of the color wished for the Marble in the water which is used to harden it, using Campeachy wood for the red, indigo for the blue and white Marble, etc.

136. M. Buisson of Bordeaux, also took out a patent on the 14th of December, 1842. He gives the following recipe.

A block of eighty inches in length and twenty-five in width, should be placed in a sheet iron basin about three feet in depth, and somewhat longer and broader than the block. Place this basin in a kiln heated to twenty-eight degrees, and maintain the same degree of heat for five hours.

At the end of this time, fill the basin with boiling water in which a solution of two and one-fifth pounds of common alum in twelve quarts of water has first been poured.

The basin should be kept filled with the same water for seventy-two hours a gentle heat being maintained in the kiln, in order that the block of Marble may become thoroughly impregnated, and acquire the hardness of Marble.

The Cognac plaster produces statuary Marble of the greatest purity.

The Rouen plaster produces the same, but with less whiteness.

For Marbles of two and a half inches in thickness for fronts of buildings, mantels of chimney pieces, pavements, etc., the same process is used, but the plaster stones must first be sawed to the required dimensions and placed in the basin at the distance of two inches apart, and baked for five hours in the kiln heated to the degree we have mentioned, after which, water prepared in the manner before described is poured upon them, and the whole is left undisturbed for twenty-four hours.

137. In order to obtain different tints, the following drugs are dissolved in the alum waters.

For black; four-fifths of a grain, Troy weight, of bulaque, three-tenths of a grain of verdigris, and as much copperas, in twelve quarts of water and two and one-fifth pounds of alum, avoirdupois.

For rose; three and a half pints of the decoction of old Brazil wood, in twelve quarts of water, and two and one-fifth pounds of alum.

For yellow; two and one-fifth pounds avoirdupois of woad or dyers' weed, in the above quantity of alum water.



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