Charles E. Firestone, Firestone & Motter Canton, Ohio

History of Structural Glazed Tile

The story of a new product is always exciting. The glazed tile structural masonry unit is this type of product.

Incised painted figures on the walls in the tombs and temples, depicting the life of the ancient Egyptians, were the beginning of the useful and decora tive structural wall .

Our concern with history is wQ.at enamellers did and how they did it. Technically, e~el is a coating of color on glass , pottery, metal, or whateve ineral substances wi11Stãn enou êãf to fuse it. There are no records of Egyptians using enamel until the Roman Egyptian period. Greeks used enamel in their jewelry and western Europeans, during the Celtic period, also enameled articles. In the first few centuries A. D., enamel was used mostly for jewelry. From the Byzantine period through the Gothic period, enamel served only for decorative motifs and jewelry. In the Orient and Far East enamel was utilized for ornaments and decoration but not for ·ntefrãl building parts. Bright colorful porcelain panels lend an interesting decora tive motif to the gabled walls of Thailand

Figure 2-1. Colored gables, Bangkok, Thailand.

9

Figure 2-2. Semiglazed structural building.

buildings (Figure 2-1). The balustrade or handrail of the stairs at the approach to the temple is the body of a snake which terminates at the newel post with a glazed, red , seven-headed serpent. The surface of the Temple of the Dawn (Wat Arun Rajarararam), almost completely covered with porcelain, made a most striking and imposing decorative exterior. 1

Throughout the world are examples of enameled or glazed decora tive units as part of buildings but not as structural bearing material. Ornaments, decorations , and motifs flourish in many countries, particularily in Western Europe and the Far

ast. The Aztec Tndians and most Indian cultures applied color to--.gargoyles, ornaments, and figures , and perhaps to some of the sun-baked building units used in their temples and shrines.

We leave the past and approach modern development of glazed-structural-facing tile units. In the late 1800's or early 1900's in northern Ohio, structural tile units 8" x 8" x 16" and 8" x 12" x 16" with a shell about 1" in thickness were manufactured. Burning the clay with its various ingredients produced this reddish-brown or purple tile with a semiglossy surface. According to information available, no ingredient was added to the clay itself or to the coaI fired units in beehive kilns to produce this particular color or semiglaze. In some instances these units had one face pressed in a mold to imitate a rock face surfacein low relief. -' Schools, factories , silos, even residences and other small buildings ma de use of this semiglazed structural building units . Some of the buildings were two and three stories high (Figure 2-2) .

10 Designing, Engineering, and Constructing with Masonry Products

( In the late 1890's or ear1y 1900's in some areas of northern / Ohio, salt was added to the beehive kiln at fire box pres~hl)úo -Pll vent a scum fõrmITIg on the bnc . A:lfhõfigh it dld not accomplis íts purpose, this appJicatiõi1'of salt in the fire box produced salt-glazed brifk. Its color varied from light yellow to dark brown wit a glossy surface, depending on the location of the unit in the kiln and intensity of the heat produced by the kiln. Neither barium nor any other foreign agent was added to the salt to give other colors. This scum cover, or salt-glazed brick, immediately became a popular and economical facing unit because it was impervious to moisture, and easy to dean, and resistant to fire. After this development, manfacturers of (3Y2" x 5" x 8" and 12" and 3Y2" x 8" x 8" and 12") structural back-up tile began to make a salt-glazed structural tile unit , thus the glazed structural facing tile industry. (Figure 2-3) This popular facing unit was used

ost1y on interiors. /. Manufacturers of glazed enamel household artides , partic­

ularily kitchen utensils, dipped treated metal into a liquid glaze material, allowed this to dry, and then baked it in a furnace under uniforrn1y controlled intense heat which formed an impervious glazed coating. If an enamel could be fused to day surfaces, rnanufacturers of structural building units saw an opportunity for various colored facing units. Experirnents resulted in the fusion of enamel and day into one unit, and so

IIII Figure 2-3. Examples of salt-glazed structural units.

the structural glazed facing-tile industry began. The dipping process developed various colors for structural glazed facing tile. Now, this tedious task demanded time and individual effort and depended entirely on the ability and agility of the

erson who dipped the product. Too, there was much waste due to human error as the process induded handling the day biscuit, dipping and drying, burning, and taking the finished

roduct from the kiln to storage or transportation vehides. Terra cotta preceded the technical application of glazed

material on a day or shale biscuit or day formo Manufacturers discussed ways and means to elirninate the

waste. A spraying process used such products as paint and germicides, so why not coat the tile by spraying the liquid glaze? In the late 1 ?20's spraying of glaze on day units began; thus, a new technique was brought into practical use. The development of spray glaze allowed economical production of a multiplicity of colors. It is possible now to achieve any hue , value and intensity in the color spectrum together with various textures of the surface. The surface texture is formed by pressing the day biscuit into a mold or by scratching and rolling to produce a rug finish on the day surface before the glaze is applied. The manufacturers of these units in northern

IOhio were the frrst in the country to produce glazed, structural facing-tile building units as a part of the structural bearing wal1. Modern gas-fired tunnel kilns produce a more \ uniform color, size, and texture of this type tile; and when fired at approximately 2100° F., the units are highly fire resi~tant.

Structural Glazed Tile Today

It remained for the structural glazed til e industry to develop the final structural, aesthetic, and load-bearing unit. Some glazed til e units are made with a continuous horizontal void and a shell of about 1/2" to 3/4 ". Other manufacturers use vertical voids varying from 1/4" to 2" in diameter. Test results of structural qualities of the units are available with respect to the allowable bearing load of the structural glazed masonry unit as part of a wall. 3

The following example (Table 2-1) of a masonry walI with structural glazed tile was taken from "Technical Notes on Brick and Tile Construction 22", May - June 1965.

Table 2-1

Allowable load A 12" wall Laid with lbs. per sq. ft.

Brick one side type M mortar (85 psi) 12,000 Glazed tile one side type S mortar (75 psi) 10,580 Masonry Bonded type N mortar (75 psi) 9,860 Other thicknesses of wall construction, pages 10 - 11

The use of these structural glazed tile units is universal however, in northern states because of dimatic conditions, the glazed units are recommended only as part of the interior surface of masonry walls. Glazed units are particular1y desirable where vehicular and human traffic is heavy and where moisture and dirt are always present.

Structural Glazed Masonry Units 11

Figure 2-4. Structural glazed tile used for wall surface designs.

Because structural glazed masonry units have hard reflective surfaces, the industry developed an acoustical tile to reduce noises where necessary. 4

With structural glazed facing tilé the wall and finish can be erected in one operation, thus saving the increased cost of labor for finished wall coatings and applications. ~­~lor, durable surface , firL.reSistance, ~~S; aCO!!§..tical, load bearing 9.ualiti,es-IUake structural ~ed~ng tjle an exceptional value for th~~ollar. ~...few new products offered as substitutes or t e wall area can match this above mentioned list of product values. Laying masonry walls unit by unit continues to be a very economical and satisfactory method of building a wall. 5 Epoxy type wall coatings offering glazed like surfaces are no better than the units to which they are applied, and time has not proven the durability of these surface finishes.

The uses of structural glazed facing til e have inc1uded many walls designed to relieve the surface appearance of one color facing tile walls. MuraIs and geometric designs give relief to the walls. The relief available is limited only by the creative abilit~ of architects and engineers. .

The elimination of the morta r joint has not been essential in the design and applications of facing tile. The availability of dirt resistaM mortars increases the use of facing tile to areas where cleanliness is a must. The value of the glazed surface with small dirt resistant joints compares favorably to sub-

stitute products with less durable finishes and little or no joints. However, the application of mortar joints make them impervious to penetration of moisture and dirt for an unlimited time.

Conc1usion

In conc1usion structural glazed masonry units become a _ primary consideration of any building, because:

1. It is economical in the ultimate building cost as it is an integral part of the structural wal!.

2. Its glazed surface provides a sanitary finish. 3. Its glazed surface is highly resistant to abrasions; there­

fore long life is assured. 4 . It is highly fire resistant, has zero flame spread, no toxic

fumes , and does not contribute fuel to burning. 5. Its aesthetic value is pleasing, many colors and textures

are available 00 the market. 6. Its density provides high sound transrnission loss through

the wall. 7. Glazed acoustical tile absorbs sound. 8. Surface maintenance is minima!. 5J.;: Q....Q. t I-

The' Future of Structural Glazed TUe

, Structural glazed tile will soon be produced on an assembly line operated by electronics. Because day deposits are widely

12 Designing, Engineering, and Constructing with Masonry Products

distributed, the same technique will probably be required as the present day strip mining. These techniques inc1ude excavating the c1ay, placing it in small carrier cars operated electronically which will take it to the assembly line where the clay will be dumped into a pulverizer, and moisture elim­inated. The dry c1ay then enters a pug mill; water and other ingredients are added for the right consistency to be extruded with pressure to the various shapes of the tile. It is then glazed by a spray, dried at a regulated temperature , carried on into the kiln, and burned at temperatures now 2100

0 F. Finally it

passes out at the kiln, is then sorted, graded, and packaged for stock or shipment. All the above operations, except for excavating and placing in stock, are assembly line techniques operated by remote control electronics and the only hand operation is the preparation of the various glaze colors.

The future of structural glazed tile is unpredictable because today glazed color units have been worked in the wall surfaces in various designs and patterns and depicting men, animaIs, birds and others (Figure 24). Glazed color tile walls will probably depict life of the people today in wall panels in low relief, as have the stone carvings in the Far East and

throughout Europe. Science and the ingenuity of man will overcome todays limitations and soon represent the most fantastic colorful walls that willlast throughout the !ife of the building.

References

1. King Phra Chao and four succeeding kings made additions to this beautiful structure 243 feet high.

2. Technical Notes , No. 16 (revised) Structural Clay Products Institute.

3. "Wall Sections," Technical Notes, No. 22 , Structural Clay Products Institute , p. 10.

4. Technical Notes, No. 5 (Sc. R. Acoustile), Structural Clay Products Institute. "A Review of Sound in Schools," American School Board Joumal, Nov. 1963, p. 40 .

5. Grimm, Clayford T. , P. E., Tables 3, 4, 5, 6, Ultimate Cost o[ Wainscot Material Used in Public Elementary School Buildings, Structural Clay Products Association of the Southwest, October, 1965.