Overhead projectors are devices used to convey visual information to an audience in a lecture hall or other meeting place. The devices have changed over the years to display text written or typed on acetate sheets as well as electronic information from a computer connected to the device. There are many techniques for using overhead projectors in your presentation including the use of overlays, chalk boarding and computerized presentations.

Chalk Boarding

Chalk boarding is a technique in which you write any information you want to relay to your audience directly on a piece of acetate sheet or roll. Chalk boarding brings a traditional classroom feel to your presentation. While you talk, write down important points you want the group to know and jot down any questions or points the group is providing to you. For a chalk boarding presentation, you need acetate sheets or a roll of acetate paper and a water-soluble transparency pen.


Highlighting is when you write down points and information on acetate film using different colored water-soluble pens. Highlighting is excellent for emphasizing information by underlining, circling, drawing check marks, bullets and other emphasis codes.


Revealing is when you cover part of the transparency with a piece of paper and then remove the paper when you get to that point in your presentation. Revealing keeps your audience from getting distracted and jumping ahead in the presentation. Revealing is ideal for directing attention to a specific point or when asking a question and then revealing the answer.


Using transparency overlays in your presentation is a way to simplify complex concepts by adding on to a basic chunk of information until you reach the complete concept. Overlays are usually colored and each transparency explains a little bit more of your presentation. They are ideal for presentations involving the development of a product line, a time line or other sequential information. After you place each layer, allow time for audience participation and feedback.

Computerized Presentations

Computerized presentations are excellent for presenting complex information that can't be relayed by writing on a piece of transparency film. Computerized presentations use a computer connected to a device that sits on top of the projector. The device displays the same information that is on the computer screen. The presentation may consist of a set of PowerPoint slides, a group of photos or a video.