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Dinosaurs used acetates and overhead projectors. You heard it here first.

Dinosaurs used acetates and overhead projectors. You heard it here first.

Wow, here’s a blast from the past!

First, the dictionary definition. Acetate is a salt or ester of acetic acid.

What’s acetic acid? Well, this is inconvenient because there is an entry for acetic acid in my dictionary, but it comes up two words from now, right after acetic. I don’t want to spoil the surprise (for both me and you) and have nothing left to talk about when I get there, so I’ll wait until then.

What’s an ester? I’m probably not going to get to that word for years. For now, I’ll just say that its some kind of organic compound. You won’t want to miss the rest of the details on esters, so stick with me over the next many years.

Acetate is also a word that means the cellulose acetate used to make textiles or plastic. That “or plastic” is where the blast from the past comes in.

Those of you who are older than, I don’t know, maybe 30 or so, can stop reading now because you’ll already be familiar with the sort of acetates I’m going to talk about. Those of you who are younger than, I don’t know, maybe 30 or so, can stop reading now because you won’t be the least bit interested in the sort of acetates I’m going to talk about. So, from this point on, I’m basically talking to myself, which, if my server statistics are correct, is pretty much what I’ve been doing all along.

Back in the old days, before the advent of notebook computers and, more importantly, before the days of video projectors that were inexpensive enough for widespread use in businesses and classrooms, business people giving presentations and university professors, as well as a few school teachers, teaching lessons often used something called an overhead projector to project text and graphics onto a screen.

When I say “screen” I don’t mean a computer screen. I know that might confuse some of the younger folk. There was a day when screen meant something completely different. A screen was simply a large vertical square or rectangle of white material on which films, slides or other images were projected using lights and lenses. If you want to see one of these types of screens in action, buy a ticket to a movie theater. They still have these old-fashioned types of screens even if their projectors are now much more new-fangled.

An overhead projector had a box containing a bright light. On the top side of the box was a piece of glass a little larger than a standard, letter-sized piece of paper that the light could shine shine through. (I just realized that some young people may not know what a letter-sized piece of paper was. In North America it’s usually 8.5” x 11”. If you don’t know what paper was, ask an adult.)

Mounted some distance above the glass was an angled box with a glass at the bottom, a lens at the front, and a mirror inside. The mirror projected stuff from the glass on top of the box below through the lens and onto a screen.

To use an overhead projector you needed letter-sized sheets of clear plastic on which was printed whatever you wanted to project on the screen. Those sheets of plastic were made of acetate and they were called, simply, acetates.

OK. History lesson over. You can go back to your video games now.

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