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CHAPTER XI Summary of Operating Precautions
THE modern motion picture projector is a very reliable mechanism. Although subjected in some instances to intense heat it will, if given proper care, last a long time and give excellent service. It is essential, however, that reasonable attention be given to the maintenance of all elements of the projector and particularly to the projection lamp. For that reason this chapter is devoted to a resume' of operating precautions which will aid the projectionist in obtaining maximum efficiency and reliability in the operation of projection lamps.
It is highly important that the correct type and combination of carbons be used. Projector carbons are manufactured to meet the specific requirements of a certain type of lamp and the combinations recommended have been carefully determined by laboratory and service tests. Best results can be obtained only when these recommendations are followed.
Carbons should always be stored in a dry place. They are porous and will absorb moisture if stored in a damp location, with the result that sputtering at the arc will be experienced. National Projector Carbons are thoroughly dry when they leave the factory but there is always the possibility of exposure to dampness during shipment or storage. For this reason, the practice of some projectionists of laying a few carbons in the lamp house or on top of a rheostat before burning is to be commended. Carbons are not perishable. A damp carbon, after being thoroughly dried, is as good as ever.
Carbon holders must be kept clean and their contact with the carbons firm. The projectionist should give frequent and careful attention to the holders, removing all effects of corrosion or burning so that
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