It is important to limit the amount of information displayed on an overhead transparency. An overhead should not appear cluttered or crowded, and it must be easy to read. Six words per line and six lines per transparency is about the maximum amount of writing desirable. Overheads do not work well as a means of regurgitating portions of a textbook. Predetermined outlines tend to work best, especially if they contain clearly defined headings.
Overhead projectors can display a great deal more than just writing.
Graphs and cartoons are a possibility, as are silhouettes and small, opaque objects. Enlarged newspaper articles and other print materials can be copied by putting the blank transparency in a photocopier. It is also possible, through a special liquid crystal display panel, to directly project a normal computer display onto the large screen. Cartoons are an excellent way of simplifying complex ideas and adding humor. With a little effort, spatial, statistical, and structural relationships can all be visualized on an overhead.