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Fifth Part.





This part of our Manual is rather a complement of details affecting Marble working than a branch of the art of the Marble worker, yet we have thought it advisable to give it place, lest the public should deem our work incomplete. It treats of the manufacture of toy marbles, of mosaics by absorption of colors, of artificial mosaics, of letters for inscriptions, of paintings upon Marble, of figures in relief, and of the coloring of Marbles. All of these details possess a certain interest, if not for Marble workers, for professional builders, and for amateurs who like to inform themselves concerning certain processes, by which results are obtained which seem to present many more difficulties than they really possess. We will begin with accounts relating to the manufacture of toy marbles.



162. Every manufacturer which supplies the wants of numerous purchasers is always sure of finding a rapid sale, and, if the manufactured article is apt to be broken or lost, it is evident that this sale will be greatly increased. This is true respecting the manufacture of toy marbles. It does not properly belong to the special province of the Marble worker, but it is one of the products of the art of Marble working, and is therefore entitled to a place in this little treatise upon the use and manufacture of articles in Marble. We give the following extract from a statement made by a manufacturer of Strasbourg.

The first operation consists in breaking the calcareous mineral into small pieces, proportioned to the size of the marbles which are to be made. This may be done in the quarry, by means of mallets resembling those used by road laborers. These pieces are then sorted and matched in equal sizes.

The second operation consists in removing the roughest asperities of the prepared pieces, thus beginning to give them a round form. During the time in which the apparatus for rounding prepares one hundred pounds, the apparatus for rough-hewing furnishes one thousand, and the millstone for scraping, two thousand pounds.

163. The operation of scraping is performed by a millstone, set in motion by some moving power; its arrangement does not differ much from those commonly used in flour mills.

The upper and moving millstone is commonly of about one-third less weight than that of ordinary millstones, in order that the pressure may not act too violently upon the asperities of the Marble, and that this millstone may present greater facilities for being raised or lowered at pleasure. For this purpose, the vertical shaft of the millstone should turn in a brass socket.

164. The most convenient dimensions of the millstones are the following:

The stationary millstone, which moves with great velocity, requires nearly or quite the power of two men for ordinary work.

The drum of the millstones is formed by a wooden hoop, four and one-third inches in width,, and placed on a level with the upper edge of the stationary millstone which it concludes in its circumference: this hoop is itself surrounded with a rim of six and a half inches in height, and is deigned to keep back the calcareous matter which the movement of the millstone may throw towards the edges.

165. The third operation (rough-hewing), consists in commencing to round the calcareous matters by means of friction against each other, and also against the cylinders of hard stone: this is done by an apparatus which is composed of a hollow cylinder of hard stone 3-28 inches in length, and 21-65 inches in diameter; the rim of the cylinder should be 3-14 inches in thickness.

Another cylinder of hard stone of 35-43 inches in length and 6-61 in diameter, having a groove in the middle to admit an iron shaft of 2-16 square inches, also aids in this operation.

The brass trays forming the cylinder are each furnished with a hinge, and have a glange extending into the inside of the cylinder; these trays are attached to the cylinder through the openings, and the cylinder is moved by a pulley.

166. To obtain the greatest effect the quantity of calcareous matter introduced into the cylinder should not exceed two-thirds of the space between the cylinders.

The proper degree of velocity is from forty to forty-five turns per minute, a greater velocity than this produces the effect of a fly wheel, which makes the substances immoveable, thus depriving them of friction.

The calcareous dust should be thrown out from time to time, as this diminishes the action of the friction of it accumulates in the cylinder.

167. The fourth operation consists in completely rounding the calcareous materials by the use of another apparatus, composed of a wooden cylinder or cask with a double bottom of 65 inches in length and 52 in diameter.

Also, a cylinder of hard stone, or several cylinders of a total length of 49-21 inches and a diameter of 6-49, with a groove of 2-16 inches in the middle to admit an iron shaft.

The staves of the interior compartment are held back to the trays by a grooving, and those of the outer compartment are confined with pins.

The calcareous matters are passed through the openings into the first and second compartment of the tray, the velocity of which should equal from forty to forty-five turns per minute.

168. The following process is employed in proportion to the degree of dead polish wished, and according to the facility of rounding the materials; this, however, is sufficient only for common marbles.

The rounding is obtained solely by friction; all the dust arising from the calcareous matter is then extracted from the cask, and a small quantity of emery in pieces of the size of a bean is mixed with it; this quickly completes the rounding and gives the desired polish.

After the manufactured Marbles are taken from the apparatus, the remainder of the emery can be extracted by the sifting of the dust, for a second use.

About two-thirds of the Marbles have a dead polish, which is attained by the use of these first four processes; the remaining third, which are of white or colored Marbles, have a shining polish, obtained by an additional process.

169. This shining polish is obtained by the process of the friction of the calcareous matters, and by the use of the second apparatus, arranged in the following manner:

The stone cylinder is rejected. In its place, a wooden cylinder covered with zinc, with its compartments also lined with zinc, is used.

After having obtained the perfect roundness and the dead polish described in the fourth operation, the Marbles are placed again in an apparatus not lined with zinc, a small quantity of emery is introduced, and about two hundred turns are given it.

The globes are then taken from this apparatus, and placed again in that lined with zinc. If they are of white Marble, a small quantity of emery dust is mixed with them to complete the polishing.

170. If the globes to be polished are of the other Marble, or of shaded, calcareous stone, a small quantity of the powder of calcined tin is introduced into the apparatus. A part of the common Marbles with a dead polish, also consists of colored globes, which take a shining polish by coloring.

171. This sixth process is executed thus:

When the fourth operation is finished, the globes are placed in the apparatus lined with zinc, and the preparations for coloring are poured upon them-not all at once, but from time to time in small quantities, and after having turned the apparatus several times.

When the coloring preparations had adhered to the globes, they are finished by giving them a final polish, which is quickly obtained by introducing a small quantity of the dust of calcined tin into the apparatus.

Despite the difficulty of coloring compact, calcareous substances durably, without heating them, this coloring may be executed both cold and dry, by the use of the following preparations:

For red, take dragons' blood in drops, reduce this gum to powder, and grind it in a glass mortar with spirits of wine or a urinous lixivium.

For the manufacture of common globes, the dragons' blood may be used alone without any preparation.

For vermilion, dissolve a quantity of vermilion in the urine and quick-lime.

For brown, take pitch mixed with turpentine.

For yellow, use the gum of gamboge, reduced to powder, and ground with spirits of wine in a glass mortar.

For yellow, the extract of saffron, dissolved in urine and quick-lime, may also be used.

For golden yellow, take equal quantities of crude salts of ammonia, white vitriol, and verdigris; grind them together, and when they are reduced to a fine powder, dissolve them in spirits of wine or a urinous lixivium.

For green, use green wax dissolved in a urinous lixivium.

172. Although these processes have been found very successful, the following improvements have lately been effected.

The pieces are roughly rounded by groovings made in the turning millstone. A wooden tray descends until the calcareous pieces just rest in the groovings with which its under surface is furnished, and which correspond exactly with the groovings of the upper surface of the turning millstone.

The depth of the groovings in the turning millstone forms half the diameter of the globes which are to be made; that of the groovings of the wooden tray forming the other half.

The wooden tray is penetrated by a vertical shaft, passing through an aperture arranged in the middle in such a manner that the shaft can turn without touching the tray. This tray can be raised or lowered at will, by a small gear adjusted to a little shaft, which raises the tray by means of two leathern straps rolling round this shaft.

The wooden tray is prevented from turning by means of brass sockets fixed by screws upon the upper part of the tray; these sockets slide in grooves arranged in the uprights of the framework.

A stream of water is constantly poured on the calcareous matter through the aperture which is arranged in the tray.

In proportion as the rounding process advances, the volume of the material diminishes, and the wooden tray descends, constantly touching, though lightly, the calcareous matters, which thus obtain a round form more speedily.

When the globes are well rounded, they are again placed between two millstones, arranged in the same manner as those for rounding with the exception that the stone tray is replaced by a wooden one; the globes thus turn between two wooden trays until the polish is obtained. This process seems to merit the preference.

173. To color the Marbles which are of a light and single shade, the following method is adopted:

The colors generally used are blue, red, and green; these mineral colors are reduced to a fine powder-The globes are placed in the millstone used in polishing, upon which a few pinches of the color are thrown, several turns are then given to the millstone; after which, the color being thus evenly spread over the surface of the globes, a few pinches of sulphur, finely crushed and sifted, are thrown upon them; the millstone is then turned more rapidly, and, as the globes become heated, the sulphur burns the color, and thus gives to the globes a finer lustre. In the manufacture of Marbles of serpentine, or other hard material, a grindstone with groovings are substituted for the millstone of which we have just spoken, or, which is better, one in brass, also grooved. For this, much more water is necessary, but the same result is obtained as in the ordinary Marbles.

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