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The work should be anchored to the backing and hung or secured to the structural frame as indicated on the setting drawings. Heavy projecting courses, whether supported by metal or not, should be well shored up from the exterior until the work on top of these courses is placed to a sufficient height.

All terra cotta should be set from outside scaffolding. It should be closely fitted and carefully laid on a solid bed of mortar. The mortar should fill all the rebates in the bed and cross joints from front and back and top to bottom, leaving no hollow spaces.

On first and second-story work, each piece after being tamped in place should have the joints raked out to a depth of 1⁄2 to 4 in. for pointing. Above the second floor it is usual to cut off excess mortar and strike the joints with a trowel or jointer. Wall copings should be set in a thick bed of mortar and well pounded down so that the mortar will fill all spaces around the webs. The vertical joints should be filled with waterproof cement. For details of wall copings, see Fig. 70.

Mortar for setting terra cotta should be composed of three parts of non-staining white Portland cement, one part by volume of hydrated lime, and eight parts fine clean sand. Plaster of Paris, or salt, should not be used in the mortar, nor any cement that swells in drying. The various materials should be carefully measured, thoroughly mixed, and the mortar used within 30 min. after mixing.

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Copings for walls up to 13 in. in thickness may be safely made in one piece, for walls 13 to 28 in. in thickness in two pieces, and for walls above 28 in. in thickness. in three or more pieces as required.

FIG. 70.

171. Pointing.-After all exterior work is completed, all raked-out joints should be carefully pointed with mortar composed of one part non-staining white Portland cement and one part clean, fine (white) sand, mixed as stiff as can be worked, forced well into the joints and tooled or troweled to produce the desired effect.

All exposed joints in projecting and overhanging features, parapet work, and work standing free, should be raked out in. and pointed with a waterproof cement mortar, such as one part non-staining Portland cement, two parts clean sand, 10% by volume of best quality lime putty, and 2% of an approved waterproofing compound, mixed in strict accordance with the manufacturer's directions. In place of the waterproofed cement mortar there are those who advocate the use of tried and approved elastic calking compounds.

172. Cleaning Down.-On completion of the work and after all mason's wedges and all centering are removed and after pointing and repointing all joints wherever necessary, the surface of the terra cotta should be cleaned down with water and a good abrasive soap or washing powder, using sufficient force in scrubbing to remove all stains. Any hard lumps of mortar may be removed by the use of a sharpened hardwood stick, but steel brushes, chisels, or other metal tools which might damage the surface by scratching, chipping, or discoloration with rust stains should not be allowed.

If "standard" terra cotta is used, and the washing does not remove the worst stains, a solution of 1 part commercial muriatic acid to 10 parts water may be used. This should never be put in any metal container on account of the liability of the acid forming rust stains-wooden pails or crockery should be used.

TILING

BY D. KNICKERBACKER BOYD

The word "tile" has its origin in the Anglo-saxon "tigel" which in turn is a derivative of the Latin "tegula," from tego-to cover. Although since appropriated to designate other products made in all sorts of shapes and from all kinds of raw materials, the term "tile" without other qualifying words or phrases still properly applies to those examples of the ceramic art which are used as a surfacing or finish for floors, walls, and ceilings, and in mural decoration on the interior or exterior of buildings.

173. Manufacture of Tiles.-Tiles are made from different kinds of clays, feldspar, and flints obtained from domestic banks and quarries or imported from other countries. These raw materials undergo a variety of refining and mixing processes before they become suitable for forming or pressing into tiles. According to the process used, tile makers distinguish between

tiles made from the materials in the plastic state and those pressed by means of machinery from the pulverized and practically dry materials-the "dust". Thus, in the one case the tiles are "made plastic," in the other case they

are "dust-pressed."

174. Unglazed Tiles.-Unglazed tiles are produced in one firing which brings them direct to their ultimate degree of vitrification, color and surface texture. The colors in these unglazed tiles are produced either by

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FIG. 71.-Illustrating decorative uses of floor tile.

the selection of clays that will burn to the desired color, or by the addition of certain oxides, such as the oxides of cobalt, chromium, etc. It lies in the nature of the raw materials and color ingredients that some of these tiles can be fired to complete vitrification, while others do not permit this. Consequently, the unglazed tiles are divided into "vitreous" and "semi-vitreous."

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FIG. 72.-An example of inlaid, or encaustic tile.

The vitreous colors in unglazed tiles include white, silver gray, celadon, green, blue green, light blue, dark blue, pink, cream and socalled "granites" of these colors. The semi-vitreous colors comprise buff, salmon, light gray, dark gray, red, chocolate, black, and "granites" of these colors.

The trade terms flint, quarry, paving, esplanade, corrugated, hydraulic, chipped face tiles, ceramic mosaic, etc., designate the various kinds of unglazed tiles mad v for different uses and decorative effects.

The principal shapes and sizes in which unglazed tiles are manufactured are:

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Encaustic tiles is a term that strictly belongs to "inlaid" tiles. These are decorative tiles produced by inlaying a figure or ornament of one color into a body of a contrasting color before firing. They are vitreous or semi-vitreous according to the colors used. The word "encaustic" is frequently misapplied as a general term for tiles; it has, however, no descriptive significance except in connection with inlaid tiles.

Ceramic mosaic is a trade designation that refers to the smaller sizes of unglazed tile, which for expediency in setting are also marketed "mounted" with the face glued to sheets of paper about 1 X 2 ft. in size; this paper is removed after the tiles have been set. The following sizes and shapes are

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termed ceramic mosaic:

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The thickness of these unglazed tiles varies with size and kind, the larger sizes and shapes having a thickness of from 2 to 1 in., while ceramic mosaics are usually 4 in. thick.

FIG.

73.-Ceramic-mosaic floor, plain field with border.

175. Glazed Tiles.-Glazed tiles are made from essentially the same materials and by the same processes as the unglazed tiles, except that they require two firings. The first firing produces the "biscuit," "bisque" or "body" made either plastic or by the dust-pressed method. This bisque is subsequently coated with the "glazing"

liquid, made from pulverized clay, feldspar, flint, and a flux. The bisques are then again placed in the kilns and subjected to high temperatures which unite glaze and bisque.

Trade custom has established the application of the word "glazed" as an exclusive designation for white glazed tiles, while the same kind of tiles in color are known by the term "enamels." Thus, the white tiles generally used for wainscot in bathrooms are "glazed" tiles, and tiles with a colored glaze are "enamels."

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The range of colors and tints in enamels is practically unlimited and the textures are of the greatest variety. Virtually any color can be procured in enamels. Moreover they are made "plain" or "mottled" in one or more colors.

Both glazed tiles and enamels are produced in bright, matt, and semi-matt or dull finish; that is to say, the bright have a surface of high gloss, the matt are entirely devoid of gloss, and the semi-matt or dull finish applies to all finishes intermediate between these extremes.

Glazed tiles and enamels are made in the following regular sizes and shapes:

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176. Trim Tiles.-For use as bases, caps, corners, moldings, door and window trim, etc., certain shaped tiles are made to match the unglazed or glazed field or body of tilework, which are designated by the terms trim or trimmers. The range of shapes obtainable in these trimmers is quite extensive and meets any utilitarian or decorative demand.

B

E

The term faience is applied to comparatively rough glazed tiles made plastic and glazed with enamels of various textures. Any special design or color effect can be carried out in faience and it is especially adapted to the decorative treatment of interior and exDterior wall surfaces.

BE

of cove bases. A and

ferred to as desirable

177. Grades of Tile.-Tiles are not manufactured in predetermined FIG. 77.-Types grades or qualities. The object of the makers is to produce but one grade, E being those re- i.e., the highest quality. But due to limitations in the processes and the in wood construction. difficulty of absolute control in firing conditions, certain variations in shades, A is also used as cove sizes, etc., take place which are inherent to tile manufacture. The tile in internal angles. makers therefore sort the tiles after they come from the kilns into different grades which experience has established as expedient. With respect to wearing and sanitary qualities no difference exists in these tiles, and appearance, size, warpage, surface blemishes, etc., alone are the basis for the sorting.

The white glazed wall tiles are graded and marketed in three grades or qualities-viz., "selected," "standard," and "commercial"-and each grade has its legitimate uses. As the term implies, the standard grade is the one used in the general run of work, such as in barber shops, cafeterias, hotels and apartment house bath rooms, moderate priced residences, etc. This grade practically represents the tiles as they come from the kiln, sorted however for uniformity in size. For the selected and commercial qualities, the tiles, as they come from the kilns, are divided into two grades. The tiles that are as nearly perfect as is possible to manufacture are chosen and marketed as "selected" for use in the finest classes of tilework, such as in high class residential work, operating rooms in hospitals, etc., while the remainder are offered as the "commercial" grade. This commercial grade finds extensive use where economy, service, sanitation, and light reflecting qualities are required and where manufacturing blemishes are of secondary importance, such as in manufacturing establishments, basement toilets, linings of shafts, etc. The enamels, vitreous tiles, and ceramic mosaic are marketed in two grades-viz., selected and commercialand the semi-vitreous tiles in one grade only, selected.

178. Crazing. In former years some manufacturers were occasionally willing to guarantee glazed or enamel tiles against crazing and some specifications even today call for tiles to be guaranteed non-crazing. This however, is no longer done by any of the large producers who are bound to recognize the limitations

of the ceramic art and realize that crazing (or crackling) of any glazed surface cannot be absolutely guarded against.

One of the causes of the phenomena known as crazing is considered to be the slightest kind of a difference in the coefficients of expansion between the materials //comprising the body and those of the glaze, which most frequently does not manifest itself until after the tile are laid. This may or may not assert itself until years after the tile are laid and sometimes will occur where the sun shines on the tile or in the proximity of radiators, while not appearing elsewhere in the same piece of work.

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The foregoing remarks refer principally to bright glaze finishes on any tile. In the 12finest decorative tiles, in faience, and in other finishes, the craze, like that of the surface effect produced by the crackled finish of the finest ceramic work, is regarded with favor.

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radius

1. 6x3" Wall tile
2. 6"x2"Cap
3. Concave angle
4 Convex angle radius
5. 5x3 Bead, radius
6. 6x3 Window sill cove
7. Left hand stop

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9. Left hand combination angle, 10. Right hand combination angle 11. 5x3 Cove, 2 radius

12. 6x26 Cove, radius

13. Concave angle, radius 14. Convex angle, 2 radius

179. Setting of Tile.-Particular attention should be paid to the methods employed to overcome shrinkage of woodwork when bathrooms or other places are to be tiled in buildings of frame construction or in any type of building with wood joists. Interior partitions should be located over those below and, where this is not possible, steel beams should be used to support the partitions surrounding bath rooms or other tile places so that no greater shrinkage will occur than at the outside walls. With such construction, lighter weight joists may be used, especially under the tile floors, assuring better seasoning and less shrinkage as well. In addition to insuring the tile work against the effects of settlement, this type of construction, through saving of labor in doubling trimmers and headers, bevelling of joists, cutting in floor boards, etc., will be found to have its economies, compensating for the increase due to the introduction of steel in place of wood where indicated.

FIG. 78.-Illustrating some of the "Trimmers" made for glazed wall tile, with key numbers.

In the case of wood construction it is recommended that coves at floor angles be in the form of combination tile on the floor tile and not on the wall tiles; also, that internal corners, if cove, be made either with separate coves or with straight joints on the combination tiles. The latter should not be alternated or woven in wood construction as any settlement or shrinkage will break the tile. These precautions do not of course apply in the case of fire resistive construction where floors and partitions are of concrete, hollow tile, or masonry, or encased steel construction. In these types of construction full range of choice in the "tile trim" may be resorted to.

Recommendations as to various types of construction are to be found in the "Standard Methods for Setting Tilework" as published by the Associated Tile Manufacturers, Beaver Falls, Pa.

GLASS AND GLAZING

BY D. KNICKERBACKER BOYD AND LEROY E. KERN

180. Raw Materials. The principal raw materials used in the manufacture of glass for general glazing purposes are: silica (white sand), lime (limestone), soda (soda-ash), charcoal, cullet (broken glass), a small quantity of alumina bearing material, and possibly decolorizing agents. These are mixed in large earthenware pots and fused at a temperature of about 3000 deg. F.

181. Physical Properties of Glass.-The composition and physical properties of glass are widely variable, not only in different varieties of glass, but also in different makes of the same type or kind of glass. Neither the mixing formulas nor the conditions of manufacture have ever been standardized and no general text book on the selection of grades or materials has been issued in this country. The results of tests made to determine the physical qualities of glass have differed greatly as is indicated by the following table:

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182. Defects or Blemishes in Glass.-The defects to which glass is subject in the process of manufacture are of two general kinds: (1) those due to imperfect polishing and grinding, and (2) those that are contained in the body of the glass itself. In cutting the large sheets into commercial sizes, care is taken to eliminate as far as is practical any defects or blemishes that may be present and to obtain the largest possible percentage of the better grades of the glass. The principal defects due to grinding and polishing are as follows: Sand Lash. This occurs near the edges of the sheet if the grinding block runs off. and is easily detected.

It is a collection of scratches

Grey Spot or Short Finish.—This is caused by insufficient grinding or polishing. It has the appearance of a collection of dust and sometimes requires a careful examination to detect.

Block Reeks or Sleets.-Caused by a coarse particle of rouge working under the polishing block. It is a smooth scratch and shines out sharply in reflected light.

Burned.-A spot where the polishing block was allowed to run dry thereby causing the surface film to start to melt. It has a finely and slightly mottled appearance on the surface but not in color.

The following are the principal defects which may be contained in the body of the glass: Bubbles.-The name describes this defect.

Seed.-Fine bubbles.

Ream. A defect the cause of which is difficult to determine. It results in a distorted image when looking at an object at an angle.

Waves. An undulation of the surface. Owing to the method of manufacture, these can not be entirely avoided in cylinder glass.

Stone. A particle of unfused material embedded in the glass. This is one of the most serious defects to which glass is subject as it makes a point of high local stress and is very likely to cause the glass to crack.

sheet.

String. An irregular shining streak made by the passage of a small "stone" during the manufacture of the

183. American and Foreign Glass.-Practically all glass now on the market, and used in connection with building, is produced in America and the following data are intended to cover the manufacture, qualities, and sizes of the various domestic glasses in general use only.

184. Grading. In the manufacture of glass only one product is aimed for and the various grades or qualities are the results of selections made in the effort to separate those sheets which are nearest perfect from those which contain some of the blemishes inherent in the process of manufacture.

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