456 WHITE IMAGE SCREENS [CH. XII 



to use white linseed oil, raw or boiled. The oil is put on with a 

 soft brush like paint. It is well to make all the brush strokes in 

 one direction, so that the lint or nap on the surface of the cloth will 

 be smoothed down in one direction. After the linseed oil is dry the 

 cloth is painted, preferably with sanitary paint and turpentine, 

 although white lead thinned with turpentine answers well. One 

 coat should be allowed to dry before adding another. It takes 

 from one to two days for each coat to dry. The screen will be 

 white and opaque with three to five coats. Care should be taken 

 to strain the paint as for the walls ( 623), then there will be no 

 rough spots ( 62 $a, 62 sb). 



If the curtain gets grimy it can be wiped off with soap and 

 water, and if necessary after it is dry, a fresh coat of the paint can 

 be put on. 



626. Roller screens. Cloth screens which have been painted 

 as just described make excellent roller curtains, for the sizing and 



62 Sa. Amounts of sizing oil and paint for a cloth screen. For oil-sizing 

 and painting a muslin screen the following times for drying in the summer, and 

 the following amounts of oil and paint were used to make a perfect screen. 

 For sizing, white raw linseed oil was used, and only one coat was applied. 



For this it required 220 cubic centimeters of the linseed oil per square meter 

 of cloth, or about one-tenth of this amount per square foot. 



For painting, a preparation of sanitary paint known as "Artists' Scenic 

 White," ready for use on screens was used, two coats were applied. It 

 required no cc. of the paint for each square meter of surface. 



It required about 36 hours for the raw oil sizing to dry; 24 hours was 

 sufficient time for a coat of the white paint to dry. The finished screen was 

 flexible and easily rolled. 



For a screen 3 meters or 10 feet square it would require for sizing and paint- 

 ing about two quarts of linseed oil and about the same amount of the "Artists' 

 Scenic White" or any other white paint for two coats of the paint. 



625b. The cloth may be sized by the use of white shellac. This is thinned 

 about half with denatured alcohol and painted on the surface just as described 

 for the oil size. It gives a good surface to paint on, but does not leave the 

 curtain so flexible. 



A hot 15% to 20% solution of white glue in water may also be used as 

 described for the oil or shellac size. This has the advantage of pasting down 

 the nap of the cloth and of giving a very good surface to paint on. It has the 

 disadvantage of expanding and contracting greatly with different conditions of 

 moisture. If the glue size is used the curtain should have at least one coat of 

 paint on the back, so that the glue size cannot be so easily affected by moisture. 



625c. The authors wish to express their appreciation for information on 

 paints and the painting of wall and cloth screens for projection, to Mr. A. E. 

 Nash, Superintendent of the Cornell University paint shop. 



