Popular Technology Volume II Part 10

6. In the United States, a great proportion of the edifices, particularly in the cities and towns, are constructed of bricks, which are usually manufactured in the vicinity of the place where they are to be used. The common clay, of which they are made, consists of a mixture of argillaceous earth and sand, with a little oxyde of iron, which causes them to turn red in burning. The material for bricks is dug up, and thrown into a large heap, late in the fall or in the winter, and exposed to the influence of the frost until spring.

7. The operation of making bricks is conducted very systematically; and, although every part of the work seems to be very simple, it requires considerable dexterity to perform it properly and to the best advantage. The workmen, in the yards about Philadelphia, are divided into _gangs_ consisting of three men and a boy. The first is called the _temperer_, who tempers the material with water and mixes it with a spade; the second is called the _wheeler_, who conveys it on a barrow to a table, where it is formed in moulds by the _moulder_, whence it is carried to the _floor_ by the boy, who is denominated the _off-bearer_.

8. The bricks are suffered to remain on the floor a day or two, or until they have become dry enough to be handled with safety. They are then removed and piled into a _hack_, under cover, in such a manner that the air may circulate freely between them. It is the business of the whole gang to remove the bricks from the floor, and also to place them in the kiln to be burned. In both cases, each one has his due proportion of labor to perform.

9. The day's work of a gang, when the weather is favorable, is to make and pile in the hack a tale of bricks, which consists of 2332, or an even 2000. The former number is called a _long tale_, and the latter, a _short tale_. Considerable skill and much care are required in burning the bricks in a proper manner; too much fire would cause them to vitrify, and too little would leave them soft, and unfit for atmospheric exposure.

10. In many places, the clay is mixed or prepared for the moulder by driving round upon it a yoke of oxen, or by means of a simple machine, consisting of a beam, into which has been driven a great number of spokes. One end of this beam is confined in a central position, while the other is moved round in a sweep by animal power.

11. Machines have also been invented by the aid of which the clay may be both mixed and moulded; but these have been very little used. A machine, however, is often employed in pressing bricks which have been formed in the usual manner. The pressing is done after the bricks have become partially dry. Such bricks are employed in facing the walls of the better kinds of structures.

12. _Tiles._--Tiles are plates used for covering roofs. They resemble bricks in their composition and mode of manufacture, and are shaped in such a manner that when placed upon a building, the edge of one tile receives that next to it, so that water cannot percolate between them.

Tiles, both of burnt clay and marble, were used by the ancients; and the former continue to be employed in various parts of Europe. Flat tiles are used for floors in many countries, and especially in Italy.

THE BRICKLAYER.

1. The particular business of the bricklayer is to lay bricks in mortar or some other cement, so as to form one solid body; but he frequently constructs the foundations of buildings in rough stones, and, in some cities, he sets hewn stone in the superstructure. In the country, plastering is likewise connected with this business.

2. Bricklaying consists in placing one brick upon another in mortar, chiefly in the construction of walls, chimneys, and ovens. In connecting these materials, especially in walls, two methods are employed, one of which is called the _English bond_, and the other, the _Flemish bond_. In the former method, the bricks are most commonly of one quality, and are laid crosswise and lengthwise in alternate rows. The bricks which are laid across the wall are called _headers_, and those which are laid in the other direction are called _stretchers_. The brick-work of the Romans was of this kind, and so are the part.i.tion-walls of many modern brick edifices.

3. The bricks employed in the walls constructed according to the Flemish method, are of two, and frequently of three, qualities. Those placed in the front, or on the external surface, are manufactured with greater care, and, in some cases, are formed in a larger mould. A wall put up on this principle may be said to consist of two thin walls composed of stretchers, with occasional headers, to unite them together. The s.p.a.ce between them, when the wall is thick, is filled in with the inferior bricks.

4. The inclosing walls of all brick edifices are erected on this plan, although they are thought to be more insecure than those constructed on the old English method. The reasons alleged for the preference, are its superior beauty, and a considerable saving in the most expensive kind of bricks. Greater security might be attained by the use of larger bricks, say sixteen inches in length, and wide and thick in proportion. Besides, an edifice constructed of well-made bricks of this size would be but little inferior in appearance to marble itself.

5. Most of the instruments used by the bricklayer are also employed by the stone-mason; and they have, therefore, been already mentioned. The particular method of laying bricks, in their various applications, can be learned by actual inspection in almost every village, city, or neighborhood, in our country, a more particular description of the bricklayer's operations is hence unnecessary.

6. Before closing this subject, however, it may be well to state that the chimney appears to be an invention comparatively modern, since the first certain notice we have of it is found in an inscription at Venice, in which it is stated that, in 1347, a great many chimneys were thrown down by an earthquake. It is conjectured that this valuable improvement originated in Italy, inasmuch as it was here that chimney-sweeping was first followed as a business.

7. Before the introduction of the chimney, it was customary to make the fire in a hole or pit in the centre or some other part of the floor, under an opening formed in the roof, which, in unfavorable weather, could be closed by a moveable covering. Among the Romans, the hearth or fire-place was located in the _atrium_ or hall, and around it the _lares_, or household G.o.ds, were placed. To avoid being infested with smoke, they burned dry wood soaked in the lees of oil.

In warming other apartments of the house, they used portable furnaces, in which were placed embers and burning coals.

8. It is said by Seneca, who flourished about the middle of the first century of the Christian era, that in his time, a particular kind of pipes was invented, and affixed to the walls of buildings, through which heat from a subterranean furnace was made to circulate. By this means, the rooms were heated more equally. In the southern parts of Italy and Spain, there are still very few chimneys. The same may be said of many other countries, where the climate is pleasant or very warm.

9. Hollinshead, who wrote during the reign of Queen Elizabeth, thus describes the rudeness of the preceding generation in the arts of life: "There were very few chimneys even in capital towns: the fire was laid to the wall, and the smoke issued out at the roof, or door, or window. The houses were wattled, and plastered over with clay; and all the furniture and utensils were of wood. The people slept on straw pallets, with a log of wood for a pillow."

THE PLASTERER.

1. In modern practice, plastering occurs in many departments of architecture. It is more particularly applied to the ceilings and interior walls of buildings, and also in rough-casting on their exterior.

2. In plastering the interior parts of buildings, three coatings of mortar are commonly applied in succession. The mortar for the _first coat_ is composed of about twelve parts of sand, six of lime, and three of hair, with a sufficient quant.i.ty of water to bring it to the proper consistence; that for the _second coat_ contains a less proportion of lime and hair; and that for the _third coat_ is composed exclusively of lime and water.

3. The mortar is applied directly to the solid wall, or to thin strips of wood called _laths_, which have been fastened with small nails to the joists, and other parts of the frame of the building. The tools with which the plasterer applies the mortar are _trowels_ of different sizes and shapes, and the _hawk_. The latter instrument is a board about a foot square, with a short handle projecting at right angles from the bottom.

4. In all well-finished rooms, cornices are run at the junction of the wall and ceiling. The materials of these cornices are lime, water, and plaster. The lime and water are first incorporated, and the plaster is added with an additional quant.i.ty of water, as it may be needed for immediate application. The composition is applied in a semifluid state, but the plaster causes it _to set_, or to become solid immediately. In the mean time, the workman applies to it, in a progressive manner, the edge of a solid piece of wood, in which an exact profile of the proposed cornice has been cut.

5. Ornaments of irregular shape are cast in moulds of wax or plaster of Paris, and these are formed on models of the proposed figures in clay. Such ornaments were formerly the productions of manual operations performed by ingenious men called _ornamental plasterers_.

The casts are all made of the purest plaster; and, after having been polished, they are fastened to the proper place with the same substance saturated with water.

6. The branch of this business called _rough-casting_, consists in applying mortar to the exterior walls of houses. The mode in which the work is performed varies but little from that adopted in plastering the walls of apartments. It, however, requires only two coats of the cement; and, when these have been applied, the surface is marked off in imitation of masonry. It is likewise sometimes colored, that it may resemble marble or some other stone.

7. The cement is commonly made of _sharp sand_ and lime; but sometimes a kind of argillaceous stone, calcined in kilns and afterwards reduced to powder by mechanical means, makes a part of the composition. The qualities of this material were first discovered by a Mr. Parker, who obtained letters patent for this application of it, in England, in 1796; hence it has been called _Parker's cement_.

THE SLATER.

1. Slate stone is valuable for the property of splitting in one direction, so as to afford fragments of a sufficient size and thinness to answer several purposes, but especially for covering houses and for writing slates. The best slates are those which are even and compact, and which absorb the least water.

2. The slates used in the United States, are obtained either from our own quarries, of which there are several, or from those of Wales, in the county of Caernarvonshire. The stone is quarried in ma.s.ses, which are afterwards split into pieces of suitable thinness. These are trimmed to an oblong figure by means of a knife and a steel edge, which act upon the slate much in the manner of a large pair of shears.

3. As it is impossible to dress all the slates to the same size without much waste of material, those engaged in their manufacture have introduced several sizes, the smallest of which are made of the fragments of the larger kinds. These are designated by names known to the trade, and to those practically conversant with the art of building.

4. The slates, when brought to market, especially those from Wales, require additional dressing to fit them for use. The manner of applying them to roofs differs but little from that employed in putting on shingles, as they are lapped over each other in the same way, and confined to their place by means of nails of a similar kind.

The nails, however, have a broader head, and are somewhat larger, varying in size to suit the dimensions of the slate. The holes in the slate for the nails are made with a steel point attached to the slater's hammer, or to his knife, technically called a _saix_.

5. Slates are preferable to shingles on account of their durability, and, in a majority of situations, for their fire-proof quality. They, however, are objectionable on account of their weight and expensiveness, and are therefore beginning to be superseded in this country by sheets of zinc, and by those of iron coated with tin.

Copper and lead are also used for roofs, but the metals just mentioned are beginning to exclude them altogether.

6. A serious objection to metal roofs has been their liability to crack, caused by the contraction and expansion of the material, in consequence of variations in the temperature of the weather; but a particular method of putting the sheets together has been lately devised, which appears to obviate the difficulty. Tiles are not used in this country, although in Europe they are very common.

[Ill.u.s.tration: PAINTER & GLAZIER.]

THE PAINTER, AND THE GLAZIER.

THE HOUSE AND SIGN PAINTER.

1. The painting which is the subject of this article relates to forming letters and sometimes ornamental and significant figures on signs, as well as to the application of paints to houses and other structures, for the purpose of improving their appearance, and of preserving them from the influence of the atmosphere and other destructive agents.

2. The substances capable of being employed by the house and sign painter, comprise a great variety of articles, derived from the mineral, vegetable, and animal kingdoms; but he ordinarily confines his selection to but few, among which are white lead, litharge, Spanish brown, yellow ochre, chrome yellow, red ochre, terra di sienna, lampblack, verdigris, linseed-oil, spirits of turpentine, and gold-leaf.

3. White lead and litharge are manufactured in great quant.i.ties at chemical works, sometimes established for the express purpose of making these and some other preparations of lead. The substances of which we are now speaking, are produced in the following manner: the lead, in form of a continued sheet, about three feet long, six inches wide, and one line in thickness, is wound spirally up in such a manner, that the coils may stand about half an inch apart.

4. The metal in this form is placed vertically in earthen vessels, at the bottom of which is some strong vinegar. These vessels, being placed in sand, horse manure, or tan, are exposed to a gentle heat, which causes the gradual evaporation of the vinegar. The vapor thus produced, a.s.sisted by the oxygen which is present, converts the exposed surface into a carbonate of lead, the substance known as white lead, or ceruse.

5. The corrosion of one of these sheets occupies from three to six weeks, during which time it is repeatedly uncoiled and sc.r.a.ped.

Litharge, or flake white, is nothing more than the densest and thickest scales produced in the manner just described. It can be obtained in a pure state from the dealers in paints, whereas the white lead of commerce is most commonly adulterated with chalk.

6. Spanish brown, yellow ochre, and terra di sienna, are earths impregnated with iron in different degrees of oxydation. Red ochre is yellow ochre burned. Chrome yellow is extensively manufactured in Baltimore, from the chromate of iron, found near that city. In chemical phraseology, the manufactured article is the chromate of lead, since the chromate is separated from the iron by the aid of a solution of the nitrate or acetate of lead.

7. Linseed-oil is obtained from flax-seed by pressure. It is afterwards filtered, and then suffered to remain at rest, to precipitate and clarify. This oil improves in quality by keeping, as it becomes, in a few years, as transparent as water. In this state, it is employed in the finest painting.

8. Before the oil is used, it is commonly boiled with a small quant.i.ty of litharge and red lead, to cause it to dry rapidly, after the paint has been applied. During the boiling, the sc.u.m is removed as fast as it rises, and this is mixed with inferior paints of a dark color.

Linseed-oil, thus prepared, is vended by dealers in paints, under the name of boiled oil.