Artificial Light: Its Influence upon Civilization Part 17

Thus the high efficiency of the modern illuminants is utilized to advantage even though their color is maintained the same as the old illuminants.

All modern illuminants emit radiant energy, which does not affect the ordinary photographic plate. This superfluous visible energy merely contributes toward glare or a superabundance of light in photographic studios. A gla.s.s has been developed which transmits virtually all the rays that affect the ordinary photographic plate and greatly reduces the accompanying inactive rays. Such a gla.s.s is naturally blue in color, because it must transmit the blue, violet, and near ultra-violet rays.

Its density has been so determined for use in bulbs for the high-efficiency tungsten lamps that the resultant light appears approximately the color of skylight without sacrificing an appreciable amount of the value of the radiant energy for ordinary photography. This gla.s.s, it is seen, transmits the so-called chemical rays and is useful in other activities where these rays alone are desired. It is used in light-therapy and in some other activities in which the chemical effects of these rays are utilized.

In the photographic dark-room a deep red light is safe for all emulsions excepting the panchromatic, and lamps of this character are standard products. An orange light is safe for many printing papers. Panchromatic plates and films are usually developed in the dark where extreme safety is desired, but a very weak deep red light is not unsafe if used cautiously. However, many photographic emulsions of this character are not very sensitive to green rays, so a green light has been used for this purpose.

A variety of colored lights are in demand for theatrical effects, displays, spectacular lighting, signaling, etc., and there are many superficial colorings available for this purpose. Few of these show any appreciable degree of permanency. Permanent superficial colorings have recently been developed, but these are secret processes unavailable for the market. For this reason colored gla.s.s is the only medium generally available where permanency is desired. For permanent lighting effects, signal gla.s.ses, colored caps, and sheets of colored gla.s.s may be used.

Tints may be obtained by means of colored reflectors. Other colored media are dyes in lacquers and in varnishes, colored inks, colored textiles, and colored pigments.

Inasmuch as colored gla.s.s enters into the development of permanent devices, it may be of interest to discuss briefly the effects of various metallic compounds which are used in gla.s.s. The exact color produced by these compounds, which are often oxides, varies slightly with the composition of the gla.s.s and method of manufacture, but this phase is only of technical interest. The coloring substances in gla.s.s may be divided into two groups. The first and largest group consists of those in which the coloring matter is in true solution; that is, the coloring is produced in the same manner as the coloring of water in which a chemical salt is dissolved. In the second group the coloring substances are present in a finely divided or colloidal state; that is, the coloring is due to the presence of particles in mechanical suspension.

In general, the lighter elements do not tend to produce colored gla.s.ses, but the heavier elements in so far as they can be incorporated into gla.s.s tend to produce intense colors. Of course, there are exceptions to this general statement.

The alkali metals, such as sodium, pota.s.sium, and lithium, do not color gla.s.s appreciably, but they have indirect effects upon the colors produced by manganese, nickel, selenium, and some other elements. Gold in sufficient amounts produces a red in gla.s.s and in low concentration a beautiful rose. It is present in the colloidal state. In the manufacture of "gold" red gla.s.s, the gla.s.s when first cooled shows no color, but on reheating the rich ruby color develops. The gla.s.s is then cooled slowly.

The gold is left in a colloidal state. Copper when added to a gla.s.s produces two colors, blue-green and red. The blue-green color, which varies in different kinds of gla.s.ses, results when the copper is fully oxidized, and the red by preventing oxidation by the presence of a reducing agent. This red may be developed by reheating as in the case of making gold ruby gla.s.s. Selenium produces orange and red colors in gla.s.s.

Silver when applied to the surface of gla.s.s produces a beautiful yellow color and it has been widely used in this manner. It has little coloring effect in gla.s.s, because it is so readily reduced, resulting in a metallic black. Uranium produces a canary yellow in soda and potash-lime gla.s.ses, which fluoresce, and these gla.s.ses may be used in the detection of ultra-violet rays. The color is topaz in lead gla.s.s. Both sulphur and carbon are used in the manufacture of pale yellow gla.s.ses.

Antimony has a weak effect, but in the presence of much lead it is used for making opaque or translucent yellow gla.s.ses. Chromium produces a green color, which is reddish in lead gla.s.s, and yellowish in soda, and potash-lime gla.s.ses.

Iron imparts a green or bluish green color to gla.s.s. It is usually present as an impurity in the ingredients of gla.s.s and its color is neutralized by adding some manganese, which produces a purple color complementary to the bluish green. This accounts for the manganese purple which develops from colorless gla.s.s exposed to ultra-violet rays.

Iron is used in "bottle green" gla.s.s. Its color is greenish blue in potash-lime gla.s.s, bluish green in soda-lime gla.s.s, and yellowish green in lead gla.s.s.

Cobalt is widely used in the production of blue gla.s.ses. It produces a violet-blue in potash-lime and soda-lime gla.s.ses and a blue in lead gla.s.ses. It appears blue, but it transmits deep red rays. For this reason when used in conjunction with a deep red gla.s.s, a filter for only the deepest red rays is obtained. Nickel produces an amethyst color in potash-lime gla.s.s, a reddish brown in soda-lime gla.s.s, and a purple in lead gla.s.s. Manganese is used largely as a "decolorizing" agent in counteracting the blue-green of iron. It produces an amethyst color in potash-lime gla.s.s and reddish violet in soda-lime and lead gla.s.ses.

These are the princ.i.p.al coloring ingredients used in the manufacture of colored gla.s.s. The staining of gla.s.s is done under lower temperatures, so that a greater variety of chemical compounds may be used. The resulting colors of metals and metallic oxides dissolved in gla.s.s depend not only upon the nature of the metal used, but also partly upon the stage of oxidation, the composition of the gla.s.s and even upon the temperature of the fusion.

In developing a gla.s.s filter the effects of the various coloring elements are determined spectrally and the various elements are varied in proper proportions until the gla.s.s of desired spectral transmission is obtained. It is seen that the coloring elements are limited and the combination of these is further limited by chemical considerations. In combining various colored gla.s.ses or various coloring elements in the same gla.s.s the "subtractive" method of color-mixture is utilized. For example, if a green gla.s.s is desired, yellowish green chromium gla.s.s may be used as a basis. By the addition of some blue-green due to copper, the yellow rays may be further subdued so that the resulting color is green.

The primary colors for this method of color-mixture are the same as those of the painter in mixing pigments--namely, purple, yellow, and blue-green. Various colors may be obtained by superposing or intimately mixing the colors. The resulting transmission (reflection in the case of reflecting media such as pigments) are those colors commonly transmitted by all the components of a mixture. Thus,

Purple and yellow = red Yellow and blue-green = green Blue-green and purple = blue

The colors produced by adding lights are based not on the "subtractive"

method but on the actual addition of colors. These primaries are red, green, and blue and it will be noted that they are the complementaries of the "subtractive" primaries. By the use of red, green, and blue lights in various proportions, all colors may be obtained in varying degrees of purity. The chief mixtures of two of the "additive" primaries produce the "subtractive" primaries. Thus,

Red and blue = purple Red and green = yellow Green and blue = blue-green

Although the coloring media which are permanent under the action of light, heat, and moisture are relatively few, by a knowledge of their spectral characteristics and other principles of color the expert is able to produce many permanent colors for lighting effects. The additive and subtractive methods are chiefly involved, but there is another method which is an "averaging" additive one. For example, if a warm tint of yellow is desired and only a dense yellow gla.s.s is available, the yellow gla.s.s may be cut into small pieces and arranged upon a colorless gla.s.s in checker-board fashion. Thus a great deal of uncolored light which is transmitted by the filter is slightly tinted by the yellow light pa.s.sing through the pieces of yellow gla.s.s. If this light is properly mixed by a diffusing gla.s.s the effect is satisfactory. These are the princ.i.p.al means of obtaining colored light by means of filters and by mixing colored lights. By using these in conjunction with the array of light-sources available it is possible to meet most of the growing demands. Of course, the ideal solution is to make the colored light directly at the light-source, and doubtless future developments which now appear remote or even impossible will supply such colored illuminants. In the meantime, much is being accomplished with the means available.

XXII

SPECTACULAR LIGHTING

Artificial light is a natural agency for producing spectacular effects.

It is readily controlled and altered in color and the brightness which it lends to displays outdoors at night renders them extremely conspicuous against the darkness of the sky. It surpa.s.ses other decorative media by the extreme range of values which may be obtained.

The decorator and painter are limited by a range of values from black to white pigments, which ordinarily represents an extreme contrast of about one to thirty. The brightnesses due to light may vary from darkness to those of the light-sources themselves. The decorator deals with secondary light--that is, light reflected by more or less diffusely reflecting objects. The lighting expert has at his command not only this secondary light but the primary light of the sources. Lighting effects everywhere attract attention and even the modern merchant testifies that adequate lighting in his store is of advertising value. In all the field of spectacular lighting the superiority of artificial light over natural light is demonstrated.

Light is a universal medium with which to attract attention and to enthrall mankind. The civilizations of all ages have realized this natural power of light. It has played a part in the festivals and triumphal processions from time immemorial and is still the most important feature of many celebrations. In the early festivals fires, candles, and oil-lamps were used and fireworks were invented for the purpose. Even to-day the pyrotechnical displays against the dark depths of the night sky hold mankind spellbound. But these evanescent notes of light have been improved upon by more permanent displays on a huge scale. Thirty years before the first practical installation of gas-lighting an exhibition of "Philosophical Fireworks" produced by the combustion of inflammable gases was given in several cities of England.

It is a long step from the array of flickering gas-flames with which the fronts of the buildings of the Soho works were illuminated a century ago to the wonderful lighting effects a century later at the Panama-Pacific Exposition. Some who saw that original display of gas-jets totaling a few hundred candle-power described it as an "occasion of extraordinary splendour." What would they have said of the modern spectacular lighting at the Exposition where Ryan used in a single effect forty-eight large search-lights aggregating 2,600,000,000 beam candle-power! No other comparison exemplifies more strikingly the progress of artificial lighting in the hundred years which have elapsed since it began to be developed.

The nature of the light-sources in the first half of the nineteenth century did not encourage spectacular or display lighting. In fact, this phase of lighting chiefly developed along with electric lamps. Of course, occasionally some temporary effect was attempted as in the case of illuminating the dome of St. Paul's Cathedral in London in 1872, but continued operation of the display was not entertained. In the case of lighting this dome a large number of ship's lanterns were used, but the result was unsatisfactory. After this unsuccessful attempt at lighting St. Paul's, a suggestion was made of "flooding it with electric light projected from various quarters." Spectacular lighting outdoors really began in earnest in the dawn of the twentieth century.

Although some of the first attempts at spectacular lighting outdoors were made with search-lights, spectacular lighting did not become generally popular until the appearance of incandescent filament lamps of reasonable efficiency and cost. The effects were obtained primarily by the use of small electric filament lamps draped in festoons or installed along the outlines and other princ.i.p.al lines of buildings and monuments.

The effect was almost wholly that of light, for the glare from the visible lamps obscured the buildings or other objects. The method is still used because it is simple and the effects may be permanently installed without requiring any attention excepting to replace burned-out lamps. However, the method has limitations from an artistic point of view because the artistic effects of painting, sculpture, and architecture cannot be combined with it very effectively. For example, the details of a monument or of a building cannot be seen distinctly enough to be appreciated. The effect is merely that of outlines or lines and patterns of points of light and is usually glaring.

The next step was to conceal these lamps behind the cornices or other projections or in nooks constructed the purpose. Light now began to mold and to paint the objects. The structures began to be visible; at least the important cornices and other details were no longer mere outlines. The introduction of the drawn-wire tungsten lamp is responsible for an innovation in spectacular lighting of this sort, for now it became possible to make concentrated light-sources so essential to projectors. Furthermore, these lighting units require very little attention after once being located. With the introduction of electric-filament lamps of this character small projectors came into use, and by means of concentrated beams of light whole buildings and monuments could be flooded with light from remote positions. The effects obtained by concealing lamps behind cornices had demonstrated that the lighting of the surfaces was the object to be realized in most cases, and when small projectors not requiring constant attention became available, a great impetus was given to flood-lighting.

When France gave to this country the Bartholdi Statue of Liberty there was no thought of having this emblem visible at night excepting for the torch held the hand of Liberty. This torch was modified at the time of the erection of the statue to accommodate the lamps available, with the result that it was merely a lantern containing a number of electric lamps. At night it was a speck of light more feeble than many surrounding sh.o.r.e lights. The statue had been lighted during festivals with festoons and outlines of lamps, but in 1915, when the freedom of the generous donor of the statue appeared to be at stake, a movement was begun which culminated in a fund for flood-lighting Liberty. The broad foundation of the statue made the lighting comparatively easy by means of banks of incandescent filament search-lights. About 225 of these units were used with a total beam candle-power of about 20,000,000. The original idea of an imitation flame for the torch was restored by building this from pieces of yellow cathedral gla.s.s of three densities.

About six hundred pieces of gla.s.s were used, the upper ones being generally of the lighter tints and the lower ones of the darker tints. A lighthouse lens was placed in this lantern so that an intense beam of light would radiate from it. The flood-lighted Statue of Liberty is now visible by night as well as by day and it has a double significance at night, for light also symbolizes independence.

Just as the Statue of Liberty stands alone in the New York Harbor so does the Woolworth Building reign supreme on lower Manhattan. Liberty proclaims independence from the bondage of man and the Woolworth Tower stands majestically in defiance of the elements as a symbol of man's growing independence of nature. This building with its cream terra-cotta surface and intricate architectural details touched here and there with buff, blue, green, red, and gold, rises 792 feet or sixty stories above the street and typifies the American spirit of conceiving and of executing great undertakings. In it are blended art, utility, and majesty. Viewed by mult.i.tudes during the day, it is a valuable advertis.e.m.e.nt for the name which stands for a national inst.i.tution. But by day it shares attention with its surroundings. If lighted at night it would stand virtually alone against the dark sky and the investment would not be wholly idle during the evening hours.

Mr. H. H. Magdsick, who designed the lighting for Liberty, planned the lighting for the Woolworth Tower, which rises 407 feet or thirty-one stories above the main building. Five hundred and fifty projectors containing tungsten filament lamps were distributed about the base of the tower and among some of the architectural details. The main architectural features of the mansard roof extending from the fifty-third to the fifty-seventh floor, the observation balcony at the fifty-eighth and the lantern structures at the fifty-ninth and sixtieth floors are covered with gold-leaf. By proper placing of the projectors a glittering effect is obtained from these gold surfaces. The crowning features of the lighting effect are the lanterns in the crest of the spire. Twenty-four 1000-watt tungsten lamps were placed behind crystal diffusing gla.s.s, which transmits the light predominantly in a horizontal direction. Thus at long distances, from which the architectural details cannot be distinguished, the brilliant crowning light is visible. An automatic dimmer was devised so that the effect of a huge varying flame was obtained. At close range, owing to the nature of the gla.s.s panels, this portion is not much brighter than the remainder of the surfaces.

When the artificial lighting is in operation the tower becomes a majestic spire of light and this magnificent Gothic structure projecting defiantly into the depths of darkness is in more than one sense a torch of modern civilization.

Many prominent buildings and monuments have burst forth in a flood of light, and their beauty and symbolism have been appreciated at night by many persons who do not notice them by day. Not only are the beautiful structures of man lighted permanently but many temporary effects are devised. Artificial lighting effects have become a prominent part in outdoor festivals, pageants, and theatricals. Candles have been a.s.sociated with Christmas trees ever since the latter came into use and naturally artificial light has been a feature in the community Christmas trees which have come into vogue in recent years. The Munic.i.p.al Christmas Tree in Chicago in 1916 was ninety feet high and was lighted with projectors. Thousands of gems taken from the Tower of Jewels at the San Francisco Exposition added life and sparkle to that of the other decorations.

[Ill.u.s.tration: The Capitol flooded with light

Luna Park, Coney Island, studded with 60,000 incandescent filament lamps

THE NEW FLOOD LIGHTING CONTRASTED WITH THE OLD OUTLINE LIGHTING]

[Ill.u.s.tration: NIAGARA FALLS FLOODED WITH LIGHT]

After the close of the recent war artificial light played a prominent part throughout the country in the joyful festivals. A jeweled arch erected in New York in honor of the returning soldiers rivaled some of the spectacles of the Panama-Pacific Exposition. The arch hung like a gigantic curtain of jewels between two obelisks, which rose to a height of eighty feet and were surmounted by jeweled forms in the shape of sunbursts. Approximately thirty thousand jewels glittered in the beams of batteries of arc-projectors. Many of the signs and devices which played a part in the "Welcome Home" movement were of striking nature and of a character to indicate permanency. The equipment of a large building consisted of more than five thousand 10-watt lamps, the entire building being outlined with stars consisting of eleven lamps each. The "Brighten Up" campaign spread throughout the country. The lighting and installation of signs and special patriotic displays, the flooding of streets and shop-windows with light without stint, produced an inspiring and uplifting effect which did much to restore cheerfulness and optimism. A glowing example was set in Washington, where the flood-lighting of the Capitol, discontinued shortly after our entrance into the war, was resumed.

In Chicago a "Victory Way" was established, with street-lighting posts on both sides of the street equipped with red, white, and blue globes surmounted by a golden G.o.ddess of Victory. One hundred and seventy-five projectors were installed along the way on the roofs and in the windows of office buildings. A brilliant, scintillating "Altar of Victory" was erected at the center of the Way. It was composed of two enormous candelabra erected one on each side of a platform ninety feet high.

These were studded with jewels and supported a curtain of jewels suspended from the altar. In the center of the curtain was a huge jeweled eagle bearing the Allied flags. This was illuminated by arc-projectors which delivered 200,000,000 beam candle-power. In addition to these there were many smaller projectors. In the top of each candelabra six large red-and-orange lamps were installed in reflectors.

These illuminated live steam which issued from the top. Surmounting the whole was a huge luminous fan formed by beams from large arc search-lights. These are only a few of the many lighting effects which welcomed the returning soldiers, but they ill.u.s.trate how much modern civilization depends upon artificial light for expressing its feelings and emotions. Throughout all these festivals light silently symbolized happiness, freedom, and advancement.

Projectors were used on a large scale in several cases before the advent of the concentrated filament lamp. W. D'A. Ryan, the leader in spectacular lighting, lighted the Niagara Falls in 1907 with batteries of arc-projectors aggregating 1,115,000,000-beam candle-power. In 1908 he used thirty arc-projectors to flood the Singer Tower in New York with light and projected light to the flag on top by means of a search-light thirty inches in diameter. Many flags waved throughout the war in the beams of search-lights, symbolizing a patriotism fully aroused. The search-light beam as it bores through the atmosphere at night is usually faintly bright, owing to the small amount of fog, dust, and smoke in the air. By providing more "substance" in the atmosphere, the beams are made to appear brighter. Following this reasoning, Ryan developed his scintillator consisting of a battery of search-light beams projected upward through clouds of steam which provided an artificial fog. This was first displayed at the Hudson-Fulton celebration with a battery of arc search-lights totaling 1,000,000,000-candle-power.

All these effects despite their magnitude were dwarfed by those at the Panama-Pacific Exposition, and inasmuch as this up to the present time represents the crowning achievement in spectacular lighting, some of the details worked out by Ryan may be of interest. In general, the lighting effects departed from the bizarre outline lighting in which glaring light-sources studded the structures. The radiant grandeur and beauty of flood-lighting from concealed light-sources was the key-note of the lighting. In this manner wonderful effects were obtained, which not only appealed to the eye and to the artistic sensibility but which were free from glare. By means of flood-lighting and relief-lighting from concealed light-sources the third dimension or depth was obtained and the architectural details and colorings were preserved. A great many different kinds of devices and lamps were used to make the night effects superior in grandeur to those of daytime. The Zone or amus.e.m.e.nt section was lighted with bare lamps in the older manner and the glaring bizarre effects contrasted the spectacular lighting of the past with the illumination of the future.

In another section the visitor was greeted with a gorgeous display of carnival spirit. Beautifully colored heraldic shields on which were written the early history of the Pacific coast were illuminated by groups of luminous arc-lamps on standards varying from twenty-five to fifty-five feet in height. The Tower of Jewels with more than a hundred thousand dangling gems was flood-lighted, and the myriads of minute reflected images of light-sources glittering against the dark sky produced an effect surpa.s.sing the dreams of imagination. Shadows and high-lights of striking contrasts or of elusive colors greeted the visitor on every hand. Individual isolated effects of light were to be found here and there. Fire hissed from the mouths of serpents and cast the spell of mobile light over the composite Spanish-Gothic-Oriental setting. A colored beam of a search-light played here and there.

Mysterious vapors rising from caldrons were in reality illuminated steam. Symbolic fountain groups did not escape the magic touch of the lighting wizard.

In the Court of the Universe great areas were illuminated by two fountains rising about a hundred feet above the sunken gardens. One of these symbolized the setting sun, the other the rising sun. The shaft and ball at the crest of each fountain were glazed with heavy opal gla.s.s imitating travertine marble and in these were installed incandescent lamps of a total candle-power of 500,000. The bal.u.s.trade seventy feet above the sunken gardens was surmounted by nearly two hundred incandescent filament search-lights. Light was everywhere, either varying in color into a harmonious scene or changing in light and shadow to mold the architecture and sculpture. The enormous gla.s.s dome of the Palace of Horticulture was converted into an astronomical sphere by projecting images upon it in such a manner that spots of light revolved; rings and comets which appeared at the horizon pa.s.sed on their way through the heavens, changing in color and disappearing again at the horizon. All these effects and many more were mirrored in the waters of the lagoons and the whole was a Wonderland indeed.

The scintillator consisted of 48 arc search-lights three feet in diameter totaling 2,600,000,000 beam candle-power. The lighting units were equipped with colored screens and the beams which radiated upward were supplied with an artificial fog by means of steam generated by a modern express locomotive. The latter was so arranged that the wheels could be driven at a speed of sixty miles per hour under brake, thereby emitting great volumes of steam and smoke, which when illuminated with various colors produced a magnificent spectacle. Over three hundred scintillator effects were worked out and this feature of fireless fireworks was widely varied. The aurora borealis and other effects created by this battery of search-lights extended for many miles. The many effects regularly available were augmented on special occasions and it is safe to state that this apparatus built upon a huge scale provided a flexibility of fireless fireworks never attained even with small-scale devices.

The lighting of the exposition can barely be touched upon in a few paragraphs and it would be difficult to describe in words even if s.p.a.ce were unlimited. It represented the power of light to beautify and to awe. It showed the feebleness of the decorator's media in comparison with light pulsating with life. It consisted of a great variety of direct, masked, concealed, and projected effects, but these were blended harmoniously with one another and with the decorative and architectural details of the structures. It was a crowning achievement of a century of public lighting which began with Murdock's initial display of a hundred flickering gas-jets. It demonstrated the powers of science in the production of light and of genius and imagination in the utilization of light. It was a silent but pulsating display of grandeur dwarfing into insignificance the aurora borealis in its most resplendent moments.