Auditorium of the Artists’ Guild Theatre, St. Louis. This little auditorium is made useful for both dramatic productions and art exhibitions by means of an ingenious device for tilting the floor, described on page 29. Above is the view toward the balcony, below the view toward the stage. Laurence Ewald, Architect.
The footlights and border lights, and, occasionally, vertical strips inside the proscenium frame at the sides, constitute the whole of the stage-lighting equipment that is more or less a part of the structure. They “go with the building.” Everything else is movable and falls into the second classification of lighting units. But, in the structure of the stage, provision must be made for the use of such additional lights. Outlets in the form of “stage pockets” are set at regular intervals in the stage floor; into these pockets, spot and flood lamps may be plugged. The pockets are set in the stage floor in two lines running up and down stage, a short distance behind the proscenium opening, at either side of it. There are usually from four to six such pockets on each side of the stage. Sometimes there is one at the back of the stage, and one or more in the fly-gallery. Occasionally, also, in houses served by alternating current, there are pockets served by a small house generator, supplying direct current for the use of arc lamps. In some theatres, also, there are pockets connected with storage batteries, intended to supply an emergency service or for use with lighting units of a voltage other than the usual 110 volts. The pockets must, of course, be carefully insulated, and covered with a hinged iron lid set flush with the floor.
The movable lights are of two general types: flood lights, for general diffused illumination, and lens lights, for concentrated, direct “spotting.” Under the first heading may be classed all special lights known, in stage parlance, as strips, floods, or bunches. Strips are small troughs, fitted with from three to ten sockets, and are used in lighting off-stage “backings,” set-pieces of scenery, and small areas where a special accent of color or intensity is wanted. Bunches, now largely obsolete, are hoods set on extension standards, fitted with ten or twelve sockets each. These have been replaced by flood lamps, burning 500 and 1,000-watt nitrogen-filled mazda bulbs. The hoods of these flood lamps have diverging sides or are fitted with a reflector behind the light, and have grooves at the front of the hood for carrying color-frames. Formerly such lamps were equipped with arc lights, but the nitrogen lamp has wholly displaced the arc in flood lighting. Its advantages are that it does not require an attendant to “feed” the light, that it can be dimmed, giving it range of intensity to make up for decreased brilliance, and that it can be burned on either direct or alternating current, without the annoying buzz of an arc light burning alternating current.
Spot lamps are mounted in closed iron hoods, emitting light from only one end through a lens. The hoods, like those of flood lamps, are set on extension standards, and can be tipped up or down and turned from side to side. Arc spots are still in general use, as the thousand-watt lamp is not sufficiently brilliant for use on large stages or for long throws. In little theatres, however, the thousand-watt spot is bright enough and has all the advantages over the arc that apply to the newer type of flood lamp. For such small stages, the principal consideration always should be centralized control, and it cannot be got with the arc light. As incandescent, gas-filled bulbs of still higher standard are developed, the arc spot will cease to be used, even in large theatres.
There is also a small variant of the spot light, known as a “baby” spotlight, burning a lamp of 150 or 250 watts. Used with care, this is one of the most valuable stage lights we have for producing delicate variations in light volume and color in particular areas of the stage. These small lights may also be dimmed.
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I have referred above to hanging hoods with thousand-watt lamps for general illumination. Where these are not made a part of the permanent lighting equipment of the theatre, they may be introduced for special scenes and effects, being hung where desired, and massed in such numbers and of such colors as needed. The hoods are equipped with chains by which they may be hung upon pipe battens and tipped as desired. They are plugged, like other movable lights, into floor pockets or fly-gallery pockets.
The color of light on the stage is obtained in three ways. Where lamps of low standard (twenty-five or forty watts) are used, as in the foots or borders, they may be coated with dyes, put up for the purpose, made with a collodion base. The burning lamp is dipped into the liquid and left alight until the dye coat has thoroughly dried and hardened. Bulbs of high standard, however, cannot be dyed, as the dye does not stand up under the intense heat generated by a lamp of one hundred or more watts. As a matter of fact, few of the commercial dyes are wholly satisfactory, even with smaller bulbs. The blues especially deteriorate under heat, either fading or cracking, or burning to a purple or black.
The rays of larger lamps, burned either in flood or spotlight hoods, are colored with gelatine mediums, held before the light in frames of proper size. The gelatine colors also fade under heat, and, being very fragile, crack and tear, and must be frequently renewed. For durability, the best color medium is a sheet of glass with the color blown in. Unfortunately such glass is very costly, cannot be had in a large range of colors, and is usually not as translucent as might be wished.