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1947-48 Theatre Catalog, 6th Edition, Page 269 (255)

1947-48 Theatre Catalog, 6th Edition
1947-48 Theatre Catalog
1947-48 Theatre Catalog, 6th Edition, Page 269
Page 269


1947-48 Theatre Catalog, 6th Edition, Page 269

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FIGURE lZ-The thinner the sheet of Plexiglas, the closer are the two reflecting surigces and the more frequently the right rebounds between them, thus making for more brilliant light use.

Thin (light rebounds more frequently)

separate case requires individual handling, but there are some considerations which may be applied effectively in many instances. The thickness of the material is of primary importance since the wider the edge, the greater the quantity of light that will enter it. However, other conditions often set narrow limits on the thickness of the material that can be used.

The character of the edge through which the light enters the sheet is also important. It should be polished and be at right angles with the sheet surfaces. A, rough, beveled or wavy surface will transmit light into the material at angles some of which permit it to escape immediately.

SOURCES OF LIGHT

Much can be said regarding the source of light. Experiments have shown that the ideal source is a line filament lamp with the edge of the plastic as close to the light source as possible (Figure 14). In practical application, however, a filament source of this type is objectionable because of the heat developed. Moreover, line filament lamps are not readily available in the length required in many applications. Because of these limitations, line filament lamps have been generally replaced with fluorescent tubes. The intensity of illumination produced by fluorescent lamps is less, since only a comparatively small amount of the light from a tube can be directed into the edge of the plastic, but the tubes are practically free from heat and are available in quite satisfactory lengths.

When more intense light is desired and fluorescent tubes are not practical, special methods of lighting with hot filament lamps may be devised. Line nlament lamps could be used by separating the plastic from the tube with a piece of tempered glass. The lamp should be placed at the focus of a metallic reflector, having a radius about one-third more than that of the tube. This reflector should be brought up around the tube, completely enclosing it except for a deep slot at the top. A piece of tempered glass placed in this slot in contact with the tube, provides the base on which the plastic rests. This arrangement secures most of the lighting value of the line filament lamp without exposing the plastic to undue heat hazard.

Another method of lighting employs small incandescent bulbs. Polished holes, about an inch larger than the diameter of the bulbs to be used, are made in the edge of the Plexiglas (Figure 15). The centers of the holes are located at a distance of about twice their diameter from each other. In use, bulbs are inserted in the holes just far enough to give maximum illumination. Light enters the sheet all around the perimeter of the holes, and the sum of these perime 1947-48 THEATRE CATALOG

Paint edge opposite light white



Frame width should be slightly wider than sheet thickness

FIGURE Iii-Light that is not diffused from CK design in a decorated sheet normally escapes from the edge opposite the light source. To prevent loss of this light, provision should be made to reflect it back into the sheet. This is done most effectively by mirroring the edge, or painting it with an opaque white point. By this means a larger portion of the light is re-diifused throughout the plastic.



Plexiglas

.Socket for

Plexiglas edge Contact between glass 5. Plexnglas

as good as possible

Tempered glass

Polished reflector

Filament tube

FIGURE l4-Experimenis have shown that the ideal source of light is a line Elmameni lamp with the edge of the plastic as close to the light source as possible. In practice, however, it is objectionable on account 0! the heat developed. Moreover, line filament lamps are not readily available in the lengths required for many applications. Figure shows a method ior using glass to reduce the effecls of heat.

FIGURE 15-Anoiher method of lighting employs small incandescent bulbs. Polished holes, about inch larger than the diameter of the bulbs to be used, are made in the edge 0! the plastic. The centers of the holes are located at or distance of about twice their diameter from each other. in use, bulbs are inserted in the holes just for enough to insure their giving maximum illumination.



FIGURE 16-Methods to provide an even light reilecled along the whole length of a bar include either the use of progressively deeper engravings (upper drawing) or engravings oi the same depth on a tapered bar (lower drawing). hays more nearly parallel to the axis of the wedge will travel farthest before they strike the engravings. A distant concentration of light may also be affected this way.

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1947-48 Theatre Catalog, 6th Edition, Page 269