Sigred Lanoux University of Southwestern Louisiana Lafayette, 70501
Practical Slides for Professional Meetings
Time and expense are common problems in lecture slide preparation. The purpose of this article is to divulge a simple, inexpensive, rapid technique for the preparation of 3% X 4 in. slides which can he easily read when projected in a fully lighted room. Transfer letters are available on paraffin coated plastic sheets and transfer easily to paper, cardboard and acetate sheets. Their transfer to glass surfaces has been a difficult and time consuming process. Advantages of slides made with these letters justified efforts to improve the transfer process.
Simple graphs can he fabricated with care. More complicated graphs and figures require the use of photographic reprod&tion techniques.
Advantages One major advantage is the cost. One sheet of 10 point "futura demibold" letters contains 901 capital letters, 1254 lower case letters, 345 numhers and 408 punctuation marks commonly found on a typewriter. Sheets of characters have dashes as guide lines under the letters and heavy borders a t each edge. These are transferrable and can he used as borders in tables. This sheet costs $1.75. Add the price of one box of projector slide cover glass (24 per box) at $3.50 and it is possible to prepare 12 slides for $5.25. One slide can be completed in less than 1 hr without leaving the direct influence of the author. Figures 4, 7 and 9 in the ACS Bulletin No. 81 were reproduced using pressure lettering in 25, 45, and 35 min, respectively. Errors can be corrected easily by lifting the wrong character with a razorblade and replacing i t with the correct character. Old slides can he updated a t any time. Glass can be recovered by soaking it in heptane to remove the characters. Slides made hv this techniaue have been . ~roiected for . 65 k n without damage.
Slide Preparation
Limitations Paraffin smudges can he observed on the glass plates and are projected on the screen, hut clarity is not reduced. At the present time the manufacturer of the most easily used pressure letters does not make full pages of capital C, H, 0 , N and P; however, production of a special sheet containing 630 C's, 840 H's, 380 O's, 380 N's and 210 P's is being considered by their management.
476
/ Journal of Chemical Education
Preparation of Glass Cover Surfaces Glass covers directly from the box have an oily film on the surface. This film can he removed by washing the surfaces with methanol or a low boiling alcohol and drying the glass on a hot plate about 60°C for 5 min. The glass is removed from the hot plate and allowed to cool to room temperature. Engineering graph paper with 5 squares per inch is suitable for use as a guide. This paper is taped to a flat surface and the treated glass is taped to the graph paper. Care should be taken since an oily spot will not accept characters. Letters are applied within a 3 X 2% in. area according to the directions supplied with the pressure lettering sheet. Attempts to transfer letters to hot glass result in a transfer of more letters than desired. A matte for the slide can he made from another piece of engineering graph paper. A cover glass is placed over the matte, excess paper is trimmed with a razor hlade and the two pieces of glass are taped together a t the edges. Slides can he updated by removing old data with a razor blade, rubbing the spot with methanol and drying on a hot plate at 60°C again. Old characters are not disturbed hv the heat. New characters can he transferred after cooling. Source of Letters Pressure letters which work best using this technique are made by Para-Tone, Inc. and marketed under the name "Para-Tipe Pressure Lettering." They can he found at most engineering supply stores. Sheet numbers of interest are: 11535, capital and lower case letters, numerals and assorted typewriter symbols; 55042, arrows, and 33059, numhers from 0 to 9 in 8, 10 and 12 point type. 1"Suggestions on Haw to Organize, Present and Illustrate a TechniealPaper," ACS Bulletin No. 8, 1961, p. 3 . 4 & 5.
