Good ones, basically forever.
I have been in some very old classrooms that likely still had the original blackboards. I can’t remember any signs of failing. Perhaps until the building is extensively remodeled, or torn down.
I’d quit if I ever had to go back to chalkboards. Whiteboards rule!
My fourth grade teacher used none of the above – instead, she used the projector for everything. When she was writing things as she was talking, she would use a sharpie on a clear projector sheet.
(See post #30)
We had a teacher that did everything with projectors too, but it was a nightmare. She’d wheel the projector in and get her notes sorted, the acetates etc, and by the time she got started the class would be half over.
I was an A/V assistant for one semester my senior year, and my main duty was cleaning those rolls of clear plastic. Our teachers used wet-erase markers, so I would spray them with water wipe off, roll ahead, spray with water, wipe off, roll ahead, etc. Very tedious, but I got to see all sorts of class notes and sometimes odd graffiti and drawings.
You know that none of that is necessary? You can write directly on the glass plate, and just wipe it off with a damp paper towel as you go–exactly as if it were a miniature chalk or white board.
You don’t need an “acetate” (it’s a transparency) at all, unless you want to prepare something like a diagram or worksheet in advance. Or if you want to write something during the class/lecture, save it, but quickly take it away, and then quickly re-introduce it to the discussion for later reference. (You can’t do that with either a chalk board or a dry-erase board.)
Or, another good use of transparencies is when students are participating in the classroom activity–they can write things on a blank transparency in their seats, and then bring it up to project to the room when it’s ready. That saves a lot of time.
I guess with a glass plate, you could use any old marker and wipe it clean with solvent.
Sure you can. You just unroll one of the maps down to cover that part of the chalkboard.
(But then you do have to make sure your class presentation is more interesting than looking at the map!)
there are three deep and four across chalk boards (on rollers or slides) for that purpose. even then math teachers would write with the right hand and erase with the left hand just to help you keep pace with your notes.
I’ve done that, but I had to reverse the map (to have the white side facing out), and when I turned it back around the springy thing inside went crazy and the map wouldn’t roll back up.
I like when cafes have their menus artistically drawn in colored chalk on blackboard. That’s an application I hope sticks around.
Occasionally I’ll have urges to eat some strange things, chalk being one of them. Chalk does not taste good, just so ya’ll know.
Pica much?
There’s plenty of gypsum it’s one of the most widely available minerals in the world, it’s main use (75% of gypsum) is to make plaster. It’s also used in a wide variety of other products I would guess that making blackboard chalk only constitutes a tiny percentage of yearly gypsum use
in an auditorium-sized classroom with more than 70 listeners, a math or physics professor might prefer using chalk. and during a 2-hour lecture, he might have gone end-to-end of a 20-foot board, erase it end-to-end, and fill it up again. you’ll see how tired your hands will be if instead you use a marker pen and try to erase it all by applying mild pressure on the board (it think the brain wants to clean a white surface more thoroughly.)
my geology professor doesn’t want any slate board shorter than 10 feet.
Quoth monstro:
The next time the urge hits you, try Tums (or generic equivalent) instead. They taste better, and are easier to chew, but it’s basically the same stuff.
And mac_bolan00, I find that whiteboards require less pressure than chalkboards, both for the writing and the erasing.
Chalk seems to be doing quite well in the hands of artists.
Take a gander at these stunning sidewalk chalk drawings.
I’ve seen plenty of photos of those drawings online, but I’m not really sure they’d work in person. The views you see online depend on very precise camera placement, and binocular vision would probably be enough to throw them off.