Asbestos

Asbestos

By John Taylor; 2006 December 10

Today is a day Marie has choir practice and I get to take care of the kids. So instead of an essay today, I include the following chilling bit of techno-cheerleading, submitted directly from the industrialist’s publicity machine to the editors of a children’s publication designed to introduce young people to the wonders of science, and published unchanged in 1922 (which means that the copyright on the article has expired, so this is one of the few of my little extras that I would not have to seek permission to reproduce should these essays ever be published). In other words, plus ca change, plus c’est la meme chose. A good percentage of the gadget articles in Popular Science will probably seem just as chilling a few decades from now; some already do, especially those touting the wonders of nanotechnology. I wonder how much was known even then about the possible deleterious effects of asbestos, and was being suppressed? Reading this article now, eighty years later, I see not just a close parallel to nanotechnology, but I see that the asbestos problem is precisely the same story, only chapter two. The little strands of asbestos are just as indestructible as carbon nanotubes. The best bit of humor about asbestos that I have seen lately is in an episode of the animated series Futurama. It is the year 3000 and in New New York old houses are being sold at a premium, advertising that the “original asbestos is still intact.”

The Story in a Lump of Asbestos

(from: The Second Book of Wonders, Rudolph and Amelie Willard Bodmer, The Wonder Book Corporation, New York, 1922, p. 313)

A Curiosity That Became a Wonderful Necessity.

For centuries asbestos was but a curiosity. Today it is a recognized commercial necessity. Developed by the efforts and the resources of a great business institution, this curio of ages now contributes to the world's progress and makes life safer and more complete.

Had someone championed asbestos earlier, had someone the vision and foresight to realize the possibilities of this mineral fifty years ago, the world today would be further along. The Chicago fire might never have happened -indeed, it is probable that fifty years hence the community fire will be a finished page, as the asbestos roof gains even wider acceptance.

What Is Asbestos?

Asbestos is one of nature's most marvelous products. It is a nugget of rock, as heavy and dense as marble, yet composed of silky fibers which can be carded, spun and woven as easily as wool, flax or silk.

Each fiber of this mineral is as light and feathery as thistle or eiderdown, yet it is so rugged and strong that for the millions of years it has existed in the earth, the forces of time have neither broken its slender thread nor marred its silken sheen.

So little is asbestos affected by the influence of time that for untold centuries it has remained in exactly the same state as it is today, while the hardest kind of rock in which it was imbedded was slowly worn away.

To look at a bunch of asbestos fiber, one would think that it would blaze up at the touch of a lighted match or dissolve when brought into contact with acids --yet it resists high temperatures and practically all commercial acids.

It looks delicate, yet it can be spun into very strong yarns. The rock is heavy, yet the fibers can be woven into cloth weighing less than sixteen ounces to the square yard.

One of the most valuable properties of this mineral is its indestructibility, which enables it to resist decay and destruction under almost every condition of heat and moisture. Compared with other materials, this property possessed by asbestos is unparalleled. Wood burns -- asbestos is uninjured by flame or temperatures to 1,500 degrees Fahrenheit. Stone disintegrates -- asbestos defies erosion. Steel rusts -- asbestos is immune to climatic or atmospheric conditions.

How Asbestos Was Formed.

While many different theories have been advanced to account for the formation of asbestos, the most generally accepted is that its origin is volcanic; that the deposits took shape during the prehistoric cooling of the earth's surface and that either water or steam is responsible for the breaking apart of the original rock formation and its rebuilding under pressure into its present fibrous state.

Asbestos is closely related to talc and soapstone. A chemist would describe it as silicate of magnesia. It has but slight traces of other minerals.

In external appearance and chemical composition, different types of asbestos fiber are much alike. The difference between them is the difference between good and bad asbestos, and will be perceived at once when the fibers are subjected to tearing, twisting and bending between the fingers.

Chrysotile, which is the fiber having the greatest commercial value, will give out silky threads of considerable length, which lend themselves to the various spinning processes necessary to the manufacture of this mineral into various products. Other forms will split up into harsh and sometimes brittle fibers which occasionally break when rubbed between the fingers.

Where Asbestos Comes From.

While asbestos occurs in some form or other in nearly every country in the world, it is never found precisely alike in any two countries. It differs not only in appearance, but also in physical and chemical characteristics according to the locality from which it comes. Some few sections of the world yield asbestos which can be used for a surprising number of purposes, but in most sections the rock, either because of its coarseness, or the ruggedness of its texture, is practically useless commercially.

In no other country has the mining of asbestos attained such proportion or success as in Canada. The excellent quality of the fiber and the richness and accessibility of the mines will enable Canada to hold the lead in the production of asbestos for years to come.

The most important of other producing countries in point of quantity is Russia, but the Russian fiber is not nearly as silky as the Canadian. It is harsher and has a yellow-brownish hue. Italy, the first country in which asbestos was produced, yields a type of this mineral which is chemically about the same as Canadian asbestos, but its physical properties are quite different. Good, long fiber is seldom found in Italian mines. Asbestos is also found in South Africa, Newfoundland, New Zealand, Queensland and South Australia and many other parts of the world -- but for one reason or another the asbestos mined in these countries does not adapt itself to commercial use so readily as Canadian asbestos.

Its Earliest Uses.

The ancients living in what we call "the "Dark Ages," held asbestos in awe, and wonderful tales about this mineral grew more wonderful with each telling.

It is related that the great Emperor Charlemagne, who ruled over a large part of Europe in the 9th century, had an asbestos table cloth with which he used to astonish his guests by throwing it into the fire and taking it out again as good as new.

About the year 1250 A. D. Marco Polo, the famous explorer, was making discoveries in many new lands of the Far East. He found that the Tartars and Chinese knew about asbestos and its fire-proof qualities, and were in the habit of using it for many purposes. They tried to fool him by telling him that it was made of the skin of the fabled Salamander (a lizard which was said to be able to live in the midst of fire).

The Growth of the Asbestos Industry.

Though the properties of asbestos were known to the early scientists, it was not until about 1870 that the first experiments were made for using it on a commercial scale. At about the same, time the first specimens of a very fine asbestos from Canada with silk-like fibers were exhibited in London. In 1878 mining operations were commenced on a smal1 scale in Canada. A lot of some fifty tons of selected crude asbestos was shipped to England, but great difficulty was encountered in selling it, as no regular demand for asbestos had been established. The uncertainty of the supply, the slight knowledge of how this mineral could be used, as well as its high price due to the very crude and slow methods of mining, were responsible for this lack of interest.

The good quality of Canadian asbestos and the ease with which it could be spun and woven, however, attracted sufficient interest to induce some enterprising capitalists to investigate this Canadian asbestos further. The more these men investigated it, the more apparent became its possibilities, and busy mining camps soon sprang up around Black Lake and Thetford in Quebec. Hand labor, which was then used in mining this rock and preparing it for manufacturing, was natural1y slow and clumsy, and as a result the cost of asbestos was high.

Experiments were begun to speed up the mining operations and bring down the cost of this mineral. Many experimental machines were instal1ed, discarded and remodeled before satisfactory results were obtained.

The difficulties to be overcome were many, as the aim was not only to replace hand labor with machines wherever possible, but also to separate the asbestos more thoroughly from the rock in which it was imbedded than had hitherto been possible.

After years of persistent effort these difficulties were overcome, and the present-day efficiency of asbestos mining and production was obtained.

How Asbestos Is Brought From the Mines.

To appreciate the size of the task of making asbestos serve civilization which has beep so successful1y mastered, one has only to take a trip through an asbestos mine. While asbestos has been mined in Canada for the last forty years, the development was very slow up to the last ten years. Now eighty-five per cent of the world's production of asbestos comes from two places in Canada, both located in the province of Quebec. One district is known as the Thetford and Black Lake District and the other as the Danville District.

As practically the whole mass of rock has to be mined, the operations are carried on in open pits or quarries. In view of this fact; the expense is largely increased when severe storms of rain or snow prevent the carrying on of the work in these open pits. Due to the severe weather conditions in Canada, there is very little production during the months of December, January, February and March -- at which time all mines are operated at a loss -- as it is necessary to remove the snow from the pits so that mining operations may be resumed as soon as the weather permits.

In order to produce 100 tons of fiber of various grades, it is necessary to quarry, blast, hoist and put through the mills 2,000 tons of rock. To handle this quantity of rock requires twelve locomotives, four steam shovels, twenty miles of track, twenty-two derricks, 300 cars and 3,000 electric horsepower to operate the machinery in the mills, which represent an investment of almost two million dollars.

How We Get Asbestos.

Asbestos mines are operated practically in the same way as large stone quarries -- the operations being carried on by a series of steps or benches, which enable the miners to dislodge large quantities of rock at each blast. The rock is so hard that it is necessary for it all to be drilled and blasted. Electricity and compressed air are used for operating the drills. The drill holes are usually put in from eight feet to twenty feet deep. The drilled holes are filled with dynamite and exploded by electric batteries, the blasts being set off at noon and night when the men leave work.

After the blasting, a number of men, known as cobbers, go into the pits. They examine all the rock that is blasted, and pick out the rock having veins of one-half inch and longer of asbestos, which they can easily dislodge from the rock with small hammers. This material is then taken to a cobbing room where it is further cleaned and sorted into three grades.

The balance of the rock in the pits is either loaded into the cars by means of steam shovels, or is hoisted from the deepest part of the pits in buckets to the surface, and from there conveyed to the mills, about a quarter of a mile from the pits. There the rock is dumped into large bins, and from these bins into very large crushers which reduce it to pieces the size of a man's fist. These pieces are then conveyed to rotary dryers in order to dry the rock. From the dryers the rock passes into "cyclones," which crush (not grind) it into very small particles.

This crushed rock containing the asbestos fiber is then taken by conveyors and passed over shaking-screens six feet wide and twelve feet long. As the fiber is much lighter than the rock, the fiber comes to the surface when the screens are shaken, and is lifted from the screens by air suction into large revolving cylinders, known as graders.

These graders separate the fiber into three different grades, one called long spinning fiber, which is used in the manufacture of various textiles; a medium grade, which is used for making  asbestos felts for roofing, firefelt for sheets for heat insulating purposes, etc., and the third grade, or short grade, is usually used for the manufacture of millboard, cements, etc. The fiber is packed in bags of 100 pounds each, and is shipped in this manner to the factories.

To convert asbestos rock into the various forms in which this mineral is now used requires millions of square feet of factory floor space, special machinery and thousands of employees.

The crude long-fiber asbestos which is used in the manufacture of various textiles is first run through heavy rollers which crush the rock without destroying the fiber. The partially broken up mineral then passes through separating machines, which automatically remove every particle of rock from the crushed mass of asbestos, leaving the asbestos fiber clean and ready for the next operation. Other machines then open up or crush it into a fine mass. It is then ready for the dusting machine which blows the fiber about and automatically takes out all of the fine dust and any remaining short particles of fiber. The resultant product is a long clean fiber ready for spinning.

Carding machines for asbestos are the result of many years of study. When you take into consideration the fact that this machine is the basis of all twisted asbestos and the starting point of all asbestos cloths, packings and roofings, etc., you can easily realize the importance of having the yarn coming from these machines correct in every detail.

The carding machine automatically weighs out the exact amount of fiber per minute, at the same time placing this fiber on a traveling apron which. feeds the machine automatically at a certain prescribed rate per minute. This machine takes the mass of fiber fed into it, straightens it out and then feeds it through another portion of the machine, which automatically twists the fiber into strands of fine yarn. The size of yarn depends entirely upon the number of strands of fiber delivered every minute by the automatic weighing attachment. It is because of this feature that a uniform quality of yarn can be assured.

These yarns are woven into cloths of various weights, thicknesses and density of weave, according to the mechanical purposes for which they are intended. They may be plain or asbesto-metallic, the former being composed solely of asbestos; the latter consisting of asbestos yarn, twisted around the strands of fine brass wire, woven into cloth.

Asbestos Packings.

The plain asbestos cloth is made into many different useful things, but the most important of these to our civilization are packings. Now the average idea of packing is one thing, but the kinds of packings asbestos fabric is used for are quite different. A packing, mechanically speaking, is a device generally shaped like a ring, to prevent leakage of steam, water or other fluids. A well-known instance is in the locomotive stuffing box, where the glistening, powerful piston-rod shoots in and out, moving the whole train. That stuffing-box contains a set of packing rings mostly made of asbestos cloth, which squeeze the rod all the time so as to prevent escape of steam and loss of power.

Asbestos cloth used in packings is coated, or, as technically called, frictioned with rubber compound and rolled up to required diameters round, or calendered where square packing is required. These packings are furnished in coil, spiral or ring form, according to the requirements of the engineers, and are thoroughly lubricated and graphited, ready for use when supplied to the trade.

The cloth with wire interwoven in the strands of asbestos is fractioned in the same manner as in the case of the packings and may be used flat for all jointing purposes and folded into gaskets for all sorts of conditions. A gasket is a sheet of flexible material put between flat - surfaces like pipe flanges to prevent leakage. In this field of packings and gaskets, asbestos has made the use of high pressure and superheated steam a success. Its great heat resisting properties successfully withstand the high temperatures, without in any way affecting its serviceability, whereas the old form of rubber, cotton and flax packings would soon be charred into uselessness.

Fire Escape Ropes.

A novel application of asbestos is in connection with ropes used by firemen and the like. Such rope is made entirely of asbestos and also of asbestos with a steel wire core. A rope with a steel wire core and three-quarter inch in diameter was found capable of carrying nearly 2,000 pounds with only one strand of the seventy or more broken. Asbestos rope made without the steel core is sufficiently strong for the ordinary applications made by the firemen.

Theater Curtains.

Asbestos cloth, plain or wire interwoven, preferably the latter, is generally used the proscenium openings of stages, as a positive barrier to the spread of flames from the stage and a protection to life and property. In this connection, it is interesting to note that Cleveland, 0hio, has the most unique fireproof theater curtain in the world in Keith's Hippodrome. It is a heavy steel frame, paneled with asbestos wood. This is one of the largest curtains in the world, being seventy-four feet wide, forty-six feet high, and weighing eleven tons. This curtain is fire-proof to such a degree that the stage might completely burn without injuring the curtain.

Filtering Uses.

Asbestos is one of the greatest known filters and is used extensively in all filtering processes, either in fiber or cloth form, more especially as a fabric, because in this form it is more tractable.

Chemical plants use it in filtering acid solutions where fabrics made of vegetable fibers or of the hair of animals would be destroyed. It has made the many wonderful electrolytic processes possible. Here it is used as diaphragms in the cells or compartments.

Most of the large portable filters for drinking waters are based on the use of asbestos. Water, no matter how discolored by dirt and sediment, can be made as clear as crystal by one or at the most two filterings. Further, asbestos cloth in one of the most prominent types of filters, has been proved greatly to reduce the number of disease-causing bacteria, by straining them from the water passing through.

Clothing and Domestic Uses.

Asbestos cloth is made up into gloves; coats, trousers, leggings, etc., for the protection of workmen in electrical furnaces, blast furnaces, glass plants, etc. For domestic purposes, into pads for protecting table tops from hot dishes, palm covers for hot irons; stove polishers, etc.

Asbestos Insulating Materials.

The medium length fibers are formed by various processes into all forms required for the insulation of heated surfaces, such as pipes, boilers, heaters, air ducts, ceilings, flues, stack linings, etc. Also for insulating refrigerators, etc., where heat must be kept out.

First. Felted Insulation.-- In this form the fibers are felted together by natural felting process with the addition of sponge or certain inert cementitious materials, which in themselves possess insulating values and are fireproof. These are used to give added mechanical strength. The material thus felted is molded into cylindrical half sections for pipes; sheets and b1ocks for larger surfaces, and rolls where a flexible material is required.

Second. Magnesia Insulation  -- In this well-known form of insulation, asbestos fibers are molded as a bond with carbonate of magnesia in proportion of eighty-five per cent magnesia carbonate and fifteen per cent fiber, into forms as above described, with the exception of the rolls. Carbonate of magnesia is used because of its lightness and the fact that like sponge, etc., in combination with asbestos fiber, it produces a structure with an infinite number of dead air cells, the basic principle of all insulation.

Third. Cellular Asbestos Insulation. This form is built up from asbestos felt or paper, later described. The felts are corrugated through regular corrugating rolls and wound over a mandrel to the required thickness for pipe covering or laid up in sheets or blocks, fastened together by means of fire-proof glue, a silicious fire-proofing material. These cellular products in the cylindrical form for pipe covering, may be formed with the cells running lengthwise with the section or circumferentially, the latter being the higher insulation, because each cell is closed against the adjoining one, preventing the free transmission of air and the loss of heat by radiation.

There are other common forms of insulation materials made from asbestos which are known as ordinary molded coverings, composed of gypsum or plaster of Paris, bonded together with fiber. These, however, are the older and more primitive forms, and because of low insulating value and inefficient mechanical strength, when applied to heated surfaces, are being abandoned by the engineering profession.

Brake Lining

Some years ago, it was discovered that asbestos possessed unusually high frictional properties and its introduction into the lining of brakes had a great deal to do with the increased efficiency of automobiles, as well as stationary machines, such as hoists, cranes and other types of machinery where friction clutches or brakes are used. It has unusual advantages over organic linings as well as iron in that it withstands the temperature caused by the friction, without breaking up, and is immune from destruction from water or oil.

Asbestos Roofing

As above stated, certain grades of short fibers of asbestos are felted into paper that is afterwards built up into asbestos roofing. A specially selected superior grade of shorter fibers, free from grit, is used; made on a regular paper-making machine into thin felts, which are saturated with a bituminous material.

For this purpose, the very best results are obtained by using a natural asphalt with non-volatile oils, and it is these two basic materials on which the great value and durability of asbestos roofing depends.

Asbestos is not subject to rot, rust or decay, therefore it possesses all of the much desired requirements for a permanent roofing felt and all that it needs to give it an indeterminate life without cost of upkeep, is a proper waterproofing element. Man-made asphalts, combined with highly volatile oils, while they may be used in the manufacture of asbestos roofing, do not make a satisfactory product. Therefore natural asphalts are used in the best types of asbestos roofing.

 Asbestos fiber is peculiar in that unlike wool or other fibers used in roofing felts, it is non-tubular, therefore it does not take the oil into the fiber tubes as in the case of organic fibers, but each fiber is individually coated on the outside and the mass so amalgamated that with the natural asphalt and non-volatile oil, the water-proofing life of the roofing fabric is prolonged indefinitely, and it is not affected by the loss of the waterproofing element by capillary attraction or the effects of the sun and air, which is the case in the ordinary felt roofing, where the water-proofing element is drawn out of the tubes and evaporated into the air, leaving the body felt to be readily oxidized and disintegrated by the elements.

Asbestos Lumber and Shingles.

Certain grades of shorter fibers of asbestos have of recent years been used very extensively in combination with Portland or hydraulic cements in the manufacture of fire-proof lumber and roofing -- the fire-proof lumber in the shape of sheets and the asbestos roofing in the form of shingles of various shapes and sizes approximating the thickness of slate.

The most approved process of manufacturing these products, and in fact the only manner in which the most durable and mechanically correct product of this nature can be made, is by mixing the asbestos fiber and the hydraulic cement dry-molding under enormous hydraulic pressure, saturating with water in order to give the proper set to the hydraulic cement, and repressing and trimming to the desired shape.

Sheets of asbestos lumber have been extensively used for large area roof coverings on steel and wooden roof structures and also for siding and partition work. The great fire hazard found in wooden shingles, the scarcity and increased cost of lumber from which these shingles are produced, and the weight and brittleness and other points of unreliability of slate, have brought the asbestos shingle into marked prominence immediately upon its being offered to the public. The asbestos shingle is light in weight, absolutely fire-proof and indestructible.

Neither of the materials used in their make-up; asbestos fiber and Portland cement, are affected by fire, temperature or exposure to elements, and the asbestos shingles will last as long as the structure upon which they are used.

Asbestos shingles differ from slate in that they will withstand a very high heat from neighboring fires, and while hot, may be wet down with water without in an way injuring them. Slate, of course, under these conditions, would crack, and wooden shingles would be readily consumed.

Fire-Resisting Cements.

Asbestos fibers are used as a bond with certain high temperature-resisting clays and certain forms of graphitic carbon, for the purpose of forming linings for stoves, ranges, furnaces, brass melting furnaces, setting up of fire brick, etc. While fire clay, even of the very best quality, under high temperatures will fuse and become brittle and lose its binding qualities, these asbestos fire-resisting cements, according to their various grades and ingredients, will withstand temperatures up to 3,000 degrees and somewhat over without being affected, thus prolonging the life of the apparatus which they line or the brick construction where they are used as a bond.

These cements are furnished in dry form for mixing with water or in plastic form all ready for use.

Fire-Resisting Molded Materials.

Certain forms of the fire-resisting cements above described are capable of being molded under hydraulic pressure for various conditions where high temperatures are to be met, such as carrying-in paddles, bottle rests and many other articles known to the glass manufacturing and electrical industries. Asbestos in this form is especially adapted for use in glass manufacturing in place of iron, because the absence of any great amount of expansion and contraction, as compared with the great amount of the same in iron, does away with the tendency found in the use of iron to cause considerable breakage in handling hot glass articles.

These pieces are also used in the jewelry trade for melting and soldering purposes.

Asbestos Used in Electrical Trade.

Asbestos fibers of different lengths, both long and short, are used in molding of pieces of innumerable designs and sizes, where a material with considerable "dielectric strength," combined with fire-resisting qualities is required. The fibers are mixed with various insulating compounds, pressed in molds into various forms to be used in electrical machinery or apparatus, such as controller linings, arc deflectors, etc. In this field alone, asbestos has gone a great way to assist in developing electrical apparatus to its modern high state of perfection.

A material which has been in use for some little time, but is taking an unusually prominent place in the electrical world is known as "ebonized asbestos wood." It is especially used in place of slate and marble for switchboards and panel boards and it has practically fifty per cent greater dielectric strength than either slate or marble, and unlike these two materials it is not brittle and easily broken, but has great mechanical strength to withstand the shocks of transportation and service.

Some of the largest power plants have equipped their switchboards throughout with ebonized asbestos wood, with the most satisfactory results in point of saving in operation, the original cost being but slightly more than slate or marble.

Asbestos' Cement.

Where a material to be molded on the job" is" required, various forms of cements in "dry form are' furnished. These cements are composed of a percentage of asbestos fiber of length and quality according to the demands of the. trade and price which it is desired to pay, mixed with cementitious fire-proofing materials, which require only the addition of water and can be applied and troweled on in much the same manner as Portland cement.

Asbestos Paper Felts.

There are certain grades of the shorter fibers which are used in the manufacture of paper felts. These fibers are mixed in a beater in very much the same way as wood pulp and other fibers, passed over a standard type of paper machine adapted to the handling of this particular fiber and made into felts of thicknesses from one-hundredth of an inch up to one-eighth of an inch.

The paper felts are used as above described, in the manufacture of cellular asbestos insulation material, fire-proof paper for lining floors, partitions, etc., of frame buildings and in the manufacture of asbestos roofing. The short fibers are also mixed with certain cementitious materials and made into asbestos boards of various thicknesses and density, in practically the same manner as cardboard is made, on what is known as a board or wet machine. These card boards vary in thickness from one thirty-second to one-half inch and are used for various forms of fire-proofing.

Asbestos Ribbon and Tape.

Asbestos paper in the form of ribbon or tape one-hundredth of an inch thick, together with asbestos yarns, is used for the covering of electric wires and cables in connection with insulating compounds, affording a high electrical resistance with fire-proof qualities.

Thin woven asbestos tape has in the last few years been produced for winding of armatures, etc., in various types of electrical apparatus, as well as the covering of wires, cables, leads, etc.

One important development of asbestos is in the fire-proof covering of individual cables running from a large power plant, where a blowout in one cable would result in the destruction of the insulation of the cables next adjoining. Here asbestos roll fire felt with cloth backing one-eighth or one-quarter inch thick, in strips three inches wide, is wound spirally around each cable, and treated with a hardening or waterproofing compound.

Asbestos Plaster and Stucco.

The very lowest grade of asbestos fibers, especially those which still contain a large percentage of serpentine rock, has found a very large use in the manufacture of plaster for exterior as well as interior purposes. There has been an unusual development of the stucco house both on terracotta blocks and wire lath over wood boards, and while there has long been a desire for this particularly attractive style of construction, it was never formerly popular, because the only available materials, sand and Portland cement, had a tendency to crack and discolor.

Asbestos stucco, however, has overcome these objections and thousands of tons are now used. In fact, it has made possible a durable stucco house of pleasing appearance. It is mixed with Portland cement and water-proofing material, in proper quantities and applied in exactly the same manner as any Portland cement mortar. It has also entered very largely into use for the interior plastering of the largest public buildings, and is now, because of its fire-proof qualities, being generally recognized throughout the large cities as a most desirable addition to fire-proof building materials.

It is almost possible to build a fireproof asbestos bungalow. At any rate, the ordinary house may be walled, ceiled, floored and roofed with asbestos boards, shingles and felts, while all fireproof roofings have a basis of asbestos. Asbestos is used also as a siding for bungalows, garages and other small buildings.

Asbestos today is an industrial, architectural and domestic necessity in the strictest interpretation of that word. There is no substitute for it. No other known material possesses the fire-resistance, durability and adaptability of asbestos. It can be woven, spun, pressed, matted, molded, in fact made up in almost any form, either alone or in combination. with other materials to produce the desired results.

Pictures and  story of Asbestos by courtesy of the H. W. Johns-Manville Company, New York

Caption: Switchboard made of asbestos wood, a product which has greater strength to resist high voltages than slate or marble, and is almost unbreakable.

A molded fuse block composed of asbestos shellac and mica. This material• has very high electrical resistance.

 Photo Captions

Caption: An asbestos theater tire curtain designed to prevent a stage fire, no matter how fierce, from passing into the auditorium.
Caption: A complete suit of asbestos worn by worker exposed to flying drops of molten metal, sparks or corrosive liquids. Asbestos, of course, is a complete protection as it is unaffected by intense heat and acids or alkalis.
Caption: Set of brake blocks made of asbestos fiber, strong wire and special binder, molded and vulcanized under enormous pressure, which grip instantly and require smaller braking surface and less effort than most non-asbestos compounds.
Caption: A handful of asbestos fibres before they are carded and spun into yarns. In this state, asbestos is very silky and beautiful.
Caption: A folding asbestos table mat protecting woodwork from being injured by hot dishes, lighted cigarettes, etc. There are also smaller table mats to put, under individual dishes, as well as stove mats with which housewives are familiar
Caption: Parts of electrical apparatus made of "electrobestos," a material composed principally of the finest asbestos fiber and therefore used for heating devises, rheostats, arc lamps, etc., where there may be intense heat.