The audio-visual handbook (1942)

Types of Visual Aids and Their Uses 57 which will prevent the light of the projector from passing through. Then select the best cutouts and let the children paste them on ordinary cover glass. This gives a silhouette effect when projected on the screen. The illustrations on this page indicate types of silhouette slides Photos Courtesy Society for Visual Education, Inc. Paper Cut-out or Silhouette Slides which may be prepared by pupils. These pictures carry a definite message which contributes materially to the subject of study. The spirited enthusiasm among the pupils who are permitted to make these slides and project them before the class is certainly evidence strong enough to warrant the use of such materials whenever possible. Etched Glass Slides. There are three principal kinds of etched glass slides. First of all it may be well to explain that etched glass is simply a piece of glass of high quality, one side of which has been roughened or etched by the use of acid or by some other method. This roughening of the otherwise slick surface of the glass provides a surface which may be used for pencil outlines or crayon work, neither of which would be satisfactory on the smooth glass. There are numerous advantages to the etched glass slides, particularly in those cases where the material on the slide is to be used but once or for a short time only. In the first place the etched glass may be used over and over again as the pencil or colored outlines on it may be removed with soap and water or with a solvent for the Colored ink, leaving the surface just as clear as it was before use. In the second place, the ease with which the etched glass slide may be used for pencil outlines causes it to be one of the preferred types for rapid work in slide making. Another convenience of the etched glass slide is that it need not be protected with a cover glass unless it is to be kept for