Mechanical an Useful arts. Present State of the Art of Mosaic.

The Year-Book of Facts in Science and Art
Exhibiting the Most Important discoveries and Improvements of the past year,
in mechanics and the useful arts; natural philosophy; electricity; chemistry; zoology and biology; geology and geography; meteorology and astronomy.
By John Timbs,
editor of "the Arcana of Science and Art."
David Bogue, Fleet Street,
We quote the following from a paper by Mr. Digby Wyatt, Architect, in the Transactions of the Society of Arts:

During the last ten years, cements, coloured with metallic oxides, have been used by Mr. Blashfield, and with a tolerably successful result, for work protected from the weather; but for out-door work, required to stand frost, it has been found necessary to employ Roman cement, of which the dark brown gives a dingy hue to all colours mixed with it. This, with some other practical difficulties, has interfered with the success of the plan. Bitumen, coloured with metallic oxides, has also been tried with Mr. Blashfield as a material for ornamental flooring. The ground work of this pattern was first cast, in any given colour, and the inter stices were afterwards filled up with bitumen of various other shades; but the method was even less successful than the former. The contraction and expansion of the bitumen soon rendered the surface uneven; the dust, trodden in, obscured the pattern, and the plan, besides being ineffectual, was expensive. Thus far I have employed the words of Mr. Ward's record of the difficulties which inevitably attend upon the outset of any ingenious revival; reserving to myself the pleasure of describing to you the progress of more successful experiments.

In the year 1839, Mr. Blashfield, having been called upon by Mr. Hope to construct an elaborate Mosaic flooring for him, at his seat at Deepdene, in Surrey, and bearing in mind the principle of the ancient "Opus incertum," the Venetian pisé, and the common Italian "Trazzo" floors, constructed a pavement which has elicited much admiration from those men of taste who have examined it. This and many similar efforts attracted more general attention to the subject, and consequently a more general demand, which paved the way for those great improvements in the art of manufacturing and laying down ornamental pavements, which it is now my pleasing duty to describe.

These ingenious inventions, or revivals, are three in number: the first is, though not precisely Mosaic in its nature, still so nearly allied to it in character and appliance that it cannot be well separated from it; I allude to the Encaustic tiles. These consisted of a fictile material made into forms of about six inches square, into the surface of which, while still in a soft state, were pressed metal dies, upon which a pattern was worked in relief: the ornament being thus indented, the intaglio or indentation was filled up with clay of a different colour. The tile was then baked, and covered with a vitreous glaze, at once enhancing and protecting the colour of the material. This art obtained universally in England from about 1300 to 1500, and was again revived in 1830, when a patent was taken out for the manufacture of similar tiles; since which period, the revival has been carried out on a large scale by Messrs. Minton and Co., of Stoke-upon-Trent, and many other manufacturers, through whose exertions this beautiful decoration has now a very extensive employment.

The second great step in the revival of the art of Mosaic to which I would allude is that made by Mr. Singer (most ably assisted by Mr. Pether) who, in the year 1829, obtained a patent for a most ingenious machine, securing a perfectly uniform Tessera, by very simple means; also greatly improving the mode of backing and laying the pavement. Mr. Singer's object was to secure a perfect imitation of the ancient Roman "Opus Tesselatum," and to this end he required to produce tesserae, or small cubes, uniform in size, hardness, colour, and surface; and to accomplish this he placed compact and manipulated clay in a machine, where, by means of powerful levers, it was subjected to great pressure, and made to exude at last out of a horizontal aperture of six" by half an inch. As it protruded it was cut into lengths of three"; and these small pieces of clay, of six inches in length by three" in breadth, and one-half in depth, were left for some days to dry. Fifteen or twenty of them were then laid upon one another, and a frame of corresponding size (across which were strained wires, crossing one another at regular intervals.) sliding vertically on two uprights, was made to pass through them, cutting out by this motion perhaps one hundred uniform tesserae. When any curved forms were required, the tesserae were placed angle-wise in a groove, and a piece of curved metal being made to pass through a quantity of them placed together, of course gave a perfect coincidence of form in the parts divided. The tesseræ were then burnt and partially vitrified, making a very nice material, and one by means of which beautiful tesselated pavement may be produced. The works already executed by Mr. Singer, among which may be noticed the flooring of the hall of the Reform Club, and the paving of a portion of Wilton Church, near Salisbury, are of great beauty.

The third great improvement, which carries one branch of the art of Mosaic to even a higher point of perfection than that attained by the ancients, was originally discovered by Mr. Prosser, of Birmingham, in the year 1840. He found that if the material of porcelain (a mixture of flint and fine clay), be reduced to a dry powder, and in that state subjected to strong pressure between steel dies, the powder is compressed into about a fourth of its bulk, and is converted into a compact substance of extraordinary hardness and density, much less porous, and much harder than the common porcelain uncompressed, and baked in the furnace. This ingenious discovery was at first applied by Mr. Prosser to the manufacture of buttons; but the happy idea having suggested itself to Mr. Blashfield, that this process was, of all others, the one best suited for the formation of tesserae, he made arrangements with Messrs. Minton and Company, who had been employed by Mr. Prosser to carry out this invention, for a supply of small cubes thus formed; and by the application of these he has much benefitted the art. These tesserae can be made of any form, either in squares for tesselation; triangles and hexagons, for imitation of the "Opus Alexandrinum;" polygons and rhomboids; or of any colour; and by means of enamelling the surface with the most brilliant tints and gold, very perfect substitutes for the ancient glass Mosaic may be produced.

In order to form a Mosaic with these tesserae, the pattern is first arranged upon a true bench, that is, a perfectly level and rectangular table, and then the tesserae are placed close together upon it, so as to form exactly the required ornament; they are then covered over with a cement, discovered by Mr. Blashfield, which sets to an extreme degree of hardness, and perfectly resists both heat and water. Previously to this discovery, Roman cement had been employed. On that are bedded strong titles, or slate backing. When the cement has set, which takes place very quickly, the pavement may be removed and laid down in the situation intended, and will be found to be perfectly true on the face, of an even hardness, imperishable, and unchanging, with an almost imperceptible joint; and, altogether, as beautiful as such a work of art can be.

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