Page:The Building News and Engineering Journal, Volume 22, 1872.djvu/229

 Marcn 15, 1872. THE BUILDING NEWS. 213 zine used for flats is of various thicknesses. No. 14 makes a pretty substantial job. A good deal of No. 12 is used, however, in practice, but to use Nos. 9 or 10, unless for a mere temporary purpose, is extremely bad, and belongs to the scamping system, unless, indeed it is done through pure ignorance. To give sheet zinc fair play it ought to be put on of such a thickness as that after its sur- face has got oxidized by exposure to the atmo- sphere, there may still be left sufficient body in it to keep itself together, and also duly serve the purpose for which it was put on. When this is properly attended to, zinc stands well for ridges, flats, and sides of roofs. For the latter purpose—viz., for sides of roofs, it may yet largely supersede the use of slates, as, if properly put on, it is not so apt to be continually going out of order. In the foregoing flat, which is above de- scribed, the breadth istakenat 15ft., but sup- posing the breadth were 30ft., all the differ- ence would be that twice the number of pieces of zinc would be required, as also two 3in. drips put in—viz., one on each side as per Z Z, Fig. 41. In the above flat, with a slope of only Sin. or so in the 8ft., I have said that a little sol- dering was necessary at certain places, but in the case of a roof with a slope of 3ft. or so every Sft., the greater part, or perhaps the whole of this soldering, could: be dispensed with, as we may see in our next. In the foregoing description of covering flat with zine, I have taken the size of zinc roll caps at 2in., but for different purposes, and in different situations, they can be had of various sizes—ltin., 1din., 1$in., &e. And instead of keeping the sheets the whole breadth, as I have above done, they may be split up the centre, which, of course, would require twice as many rolls, the distance between them being only in that case about half the above. In above illustration I have also set up the zine 4in. and 3in. high on the sides, which allows it to overlap as per V V, Fig. 37, but some plumbers only set it up as high as A, Fig. 37, which may do where it is not much exposed, and flat has also a good slope. Instead of doing front corners of sheets as per Fig. 38, it has been hitherto the custom with many plumbers to Solder the front edges of the different sheets together (instead of keeping themall separate as per Fig. 38) which, of course, has the effect of causing them to give way here, as they often do. Fig. 42 issection across flat of zine roll- cap, in contrast to skeleton view of lead roll shown by Fig. 30, p. 199; and: Fig. 45 is sketch of zine flat when finished, just as Fig. . 33 showed lead flat when finished. In covering broad flats with lead a wooden block, or frame, with saddle piece is often run up the centre as per Fig. 40, only, as in using lead, the lead rolls have to be turned up against it, as per B B, Fig. 44 ; the block is often made sloping as shown, so that lead rolls may be turned up easier. In reference to correspondence which has taken place about the style of laying lead in stone cornice gutter, explained at p. 95, I may observe that generally speaking the plumber has little or no control over the style of laying gutters in stone cornice re- ferred to, as he has to make his lead to suit the channel, and in accordance with the architect’s plan. If, as is often the case, the architect only allows one outlet for the rain water, and orders the gutter channel to be all inclined to one end, then the plumber is forced tolay his gutterall in one piece, as described at p. 95 ; butif the architect allows two rain-water pipes—yviz., one at each end, then the plumber can lay his gutter in two pieces with a roll, an overlap, or a saddle in the middle. And, as regards stone cornice gutters at p. 170, if two pipes are putin, then, as in many cases, there is no necessity to lay any gutter along front of chimmey shown at p. 170, as the gutter-lead can be made to Stop off at each front corner of chimney, which causes gutter to be in two pieces, and each piece so much shorter. Or to take another plan, supposing the gutter channel at p. 95 were inclined from each end and made with a slope down towards the middle, then even with one rain-water pipe, the gutter lead could be put in in two pieces, either by using a breeches pipe, as per Fig. 45, or by letting down two short pipes into one rain-water head, as per Fig. 46. Erratum.—At p. 199, third column, twenty-second line, for ‘‘ wooden, baton- shouldered iron spikes ” read ‘‘ wooden baton, shouldered-iron-spikes,” this ‘‘ baton” or wood-roll being supported by the shouldered- iron-spikes, as per Fig. 21. (To be continued.) ee es DECORATIVE PROCESSES. STAINING, GRAINING, AND INLAYING OF WOODS AND MARBLES. By An ExPerRreENCED WORKMAN. (Continued from page 191.) HE imitation inlaying of marbles, of which we are now about to treat, is of necessity a very different and much more difficult process than the inlaying of woods, and will require a different class of designs and method of working. This will at once be evident if we consider the nature of the material. Solid cubes, or thin veneers of wood, are, of course, much easier cut into intricate ornamental forms than marble and stone would be, this fact alone necessitating the use of designs best adapted to the capabilities of the material used. Marbles may, of course, be used in small cubes as mosaic ; but that method or process is of necessity from its very nature so expensive that works so executed are rare and very costly. In fact, the inlaying of marbles is in any case very costly, from the large amount of labour required to shape and fit the various parts together ; cutting, grinding, and polish- ing are operations requiring the expenditure of much labour, which is money. ‘Ihe class of designs suitable for imitation in marble should in all cases be such as would or could be worked in the real marbles. A greater breadth and boldness of treatment are required than if we were dealing with wood ; sim- plicity of design is in this case an element of success, not only as to its cost, but as a matter of taste and facility of execution. With regard to colour, we have in marble an infinite variety of shades and tints, and the difficulty is not what special marble we must use, but which, out of the great number at our command, will best suit our purpose. There are several methods of imitating marbles, some of which are now accepted as legitimate aids in architectural construction, such as scagliola, enamelled slate, &c., and several patents have been taken out for com- positions having this object in view. Scagliola is undoubtedly the best of these manufactured imitations. It is composed of the best plaster of Paris, alabaster, felspar, certain colouring mediums, cements, &c. As a rule, ‘a wood or plaster base is prepared, or a brick pillar or pilaster is the groundwork, upon which this composition is worked. If sienna marble is to be imitated, portions of the cement are coloured of the various tints and shades of yellow, cream colour, pink, gray, and stone colours, with dark purple, brown, and black for the veins ; these are all kept in a moist state, for convenience of working, by covering with wet cloths. Portions of each of these coloured cements are used as the work progresses to form thé variegated ap- pearance of the marble, and while the work is soft, small and large pieces of white ala- baster, felspar, and hornblende are inserted ; these, being semi-transparent, give an appear- ance of reality to the imitation it would not otherwise have. After the whole has acquired a sufficient hardness, it is cut down to a smooth level surface, and polished in the usual manner. Verd antique is the best marble in its form and character for imitation in scagliola, and we have some examples so excellently done that it would require a very skilful judge to tell the difference between the real and the imitation; but, indeed, scagliola may justly be called artificial marble. Enamelled slate is another imitation of marble which has been brought to great per- fection by the persevering efforts of Mr. Magnus, of Pimlico, some very beautiful examples of this manufacture being exhibited by him in the Exhibitions of 1851 and 1862. Since the expiration of Mr. Magnus’s patent rights, several manufactories haye been es- tablished, and enamelled slate chimney-pieces have become an article of commerce. As a matter of course, in this process, as inscagliola, and other methods of imitation, the quantity of the article will depend in a very great measure upon the skill and taste of the artist employed. We haye seen some admirable specimens produced by Mr. Magnus, but the great bulk of the work in the market is poor in character and finish. ‘The principle upon which this work is executed is somewhat like the method used by the Japanese ; the colours are smeared upon the slate with a feather and brushes in a thick body and in irregular streaks; when one colour is dry another is added; this forms an irregular and uneven surface. Over this again the whole surface may be painted with the tint of colour most prevalent in the marble to be represented. We may note that white is generally the first pigment put upon the sur- face of the slate, and the more irregular and lumpy it is laid on, the better the effect will be at the finish. The article is now put into a drying-room or stove, in which the heat is regulated so as to thoroughly harden the paint and yet not hot enough to split the slate ; when sufficiently stoved, the article is taken out and allowed to cool. It is then ground down to a level surface with pumice stone or other polishing grit. This cutting down or grinding brings out the vein or mark- ings of the marble, according to the form or manner in which it has been worked ; the pro- jecting parts being cut down to a level, the colour first put on the slate is reached, leaving portions of the whole of the colours used in streaks, veins, and shades, on its surface and edges. Thisis rather difficult to explain, but we may illustrate it by a fact which will be better understood. Inthe house or coach-painters workshops, there is generally one portion of the walls on which the men will rub the paint out of their brushes when either taking them out of the brush-tub or putting them in; the paint on this wall, in course of time, becomes of great thickness, sometimesas much as an inch; the irregularity of the brick wall gives its form to this mass of paint which it retains ; the immense quantity of coats of paint of all colours and shades thus accumulated can scarcely be estimated. Now, when this thick cake of paint is taken off the wall and cut into slabs or veneers, it will be found to be most beautifully variegated, and marked and veined in rings, &e., according to the rough- ness and uneyenness of the wall; so it is with enamelled slate. The enamel, after being rubbed down may be again touched up with transparent colour, stoved and polished, or may receive two coats of polishing varnish, then be stoved and polished similar to the Japan tea trays. The chief drawback to this manufacture, as an imitation, is its opacity, which gives it a common or poor look ; there is a depth and semi-transparency about real marble entirely absent in the enamel, by which test it may at once be discerned. We have before us at this present writing two specifications of patents for compositions for imitating marble, veneer, &c. ‘The two are almost identical, but one only received provisional protection, while the other was patented on the 7th of January, 1870; both received provisional protection in 1869, within three months of each other. Mr. Edward Snell, the patentee, describes his invention as