Motion Picture Herald (Jul-Aug 1936)

EQUIPMENT and OPERATION A DEPARTMENT OF PRACTICAL MAINTENANCE AND OPERATING SERVICE • 0 CONDUCTED RV J. T. KNIGHT, JR. Midsummer Reminders About Roofs, Light Shock, Air Comfort • It may be hotter'n h-ot where you are, but now's the very time to consider these matters, so pull up a chair alongside a cool drink and The extreme heat that we are all experiencing this summer is undoubtedly going to be remembered this fall during the rainy season. Extremely high temperatures do great damage to roofs, particularly the built-up type, so don't be surprised if there are leaks in the theatre this fall. Each theatre manager is warned now to check and see for himself just what is happening to the roof of his theatre. A few dollars spent in September is much the wiser policy than waiting for leaks to appear. A leak may do a good deal of damage before it is called to the attention of the manager. Suspended plaster once thoroughly soaked with water is never positively safe, even though there have been instances where it has remained in place for some years. In discussing roofs with managers, I have found that few know "what it is all about." To start with, let's be sure everyone knows what asphalt is and what tar is. ASPHALT Asphalt is a product of nature found in large deposits sometimes called lakes, in Trinidad and Venezuela. It is a hydrocarbon, but it has some quantity of clay and water in it. It is always put through a refining process before being used for roofing. The various oils contained in the asphalt evaporate more slowly than those found in tar, consequently asphalt remains more plastic for a longer period of time, and when applied to roofs has a longer life and greater flexibility than tar. COAL TAR Coal tar, or just tar, is the deposit obtained from blast furnaces, or by distilling coal, or from the manufacture of coke and gas. The crude tar as it comes out of the furnace is again distilled, and from the second process we obtain benzene and naphthalene. The remaining substance, after distilling the second or third time, is called pitch, and this is the material we use for some roofing. Tar pitch is also a hydrocarbon and is impervious to and repels water. BUILT-UP ROOFS Most theatres have built-up roofs. Builtup roofs are laid on wood decks, concrete decks, or gypsum slabs. Most built-up roofs are composed of from two to five layers or plys of felt, sometimes called rag felt, or jute saturated with coal tar pitch or asphalt. Each layer or ply is laid in a mopping of hot tar or asphalt. The final ply of felt is very thoroughly mopped with tar or asphalt, and while the tar or asphalt is still hot or soft it is covered with crushed slag, stone or clean gravel. Built-up roofs finished with slag, stone or gravel are not intended to stand much traffic, so don't permit ushers or any employes to use such roofs as places of rest cr recreation. In laying a built-up roof, a layer of sheathing paper is first laid down on the deck. This sheathing paper should be lapped at least 2 inches. On top of the sheathing is laid two layers of tarred felt ; if the roof deck is of wood, these layers should be nailed to the deck. The two layers should be lapped from 15 to 18 inches. After this comes the first mopping of tar, then a layer of felt lapped about 20 inches, another mopping of tar or asphalt, another layer of felt lapped from 22 to 24 inches, another mopping of tar or asphalt, and then the final layer of felt lapped 24 inches. A final mopping of tar or asphalt and gravel is applied and you have a five-ply roof that should stand up for fifteen or twenty years. I have been told that theatre men won't read much during the summer. Having been forwarned, you may wonder why a subject like roofs was selected to write about. Well, the maintenance man knows no seasons. There is a time for every job, and the dry season is the time to think of roofs. Don't wait for rain to tell you that your roofs needs repairing! Don't be like the man found sitting in his cabin under an umbrella who, when asked why he did not fix his roof, replied, "Yes, my roof leaks, but when it ain't rainin' I don't give a damn, and when it's rainin' I can't fix it anyhow." ILLUMINATION OF THE AUDITORIUM there is another angle of theatre operation that to me is always emphasized in the summertime, and that is the general running illumination in theatre auditoriums. By running illumination I mean the lights that are burning during the time when pictures are being projected on the screen. Most auditoriums are entirely too dark. The contrast between the light level in the auditorium and the bright sun light on the street is always greater in the summer than in the winter. The contrast is so sharp, especially in the theatre with a very small lobby and foyer, that the effect is almost blinding. It is my opinion that one of the smartest showmanship angles of summer theatre operation is a complete re-adjustment of the theatre lighting. Many an old theatre could be greatly improved by the expenditure of a few hundred dollars on the revamping of the auditorium lighting scheme. Instead of listening to some local salesman who would like to get rid of some slow-moving fixtures, and is willing to give you a price on them, why not send your problems to the largest lighting laboratory in the country for their advice, [Nela Park Engineering Department, General Electric Company, Cleveland] ? I, July 25, 1936 19