Why are chalkboards often green?

[Bluffcityguy]

@SilverBridge

OK, just another memory here about chalk and erasers in Catholic school.

Does anybody remember putting a piece of chalk in between the sections of eraser so when Sister Mary *****(Cleophus, Madonna, and Lawrence all come to mind)…

Sister Mary Elephant, of course!

Cheers,

bcg

[Bluffcityguy]

@Balthisar

I’m not sure if there’s a special state law that permits it, but the nearby village of Frankenmuth, Michigan, actually uses European-style signs for everything. The typeface, colors, shapes, everything. They’re not decorative; other than the speed-limit signs on the way into the city, there’re no other US-style traffic signs.

I’m not sure if the conventions I noted in the post you responded to are legal mandates or just generally accepted standards. IIRC, Frankenmuth is a fairly big tourist draw, and I wouldn’t be surprised if they got special legislation permitting those signs there.

Cheers,

BCG

[CC]

@flodnak

…
But I still prefer a good old-fashioned chalkboard. It’s an aesthetic thing.
…

I will second that. Especially with a type of chalkboard that is made of a very slightly dampening material - not glass hard - there’s a great feel and sound to using them. The chattering of the chalk on the board, the feel of it all - ahhh, teaching has so many rewards!

[Solfy]

@WarmNPrickly

A sign that says “don’t use acetone” will quickly be ignored. Sure, the older students might know better, but the guard changes in grad school so often that little useful information gets passed down. Acetone bottles are scattered around any synthetic lab for the explicit purpose of cleaning organic residue. When your writing on the board, your activily focusing on the subject. Grabbing the acetone bottle is pure instinct.

Chalk is the least of our worries in a chem lab. It doesn’t stay in the air long and even if it gets into your reaction is not soluble and usually dry. Even so, if random stuff is flying into your reaction, your methodology needs work. I knew a guy that had his laptop flagged at the airport because it tested positive for nitrates. Chalk is least of our worries in a chem lab.

There are no boards of any sort in our labs. Who needs them when everyone’s got a Sharpie in their pocket and a perfectly good hood sash to scribble all over?

[jasonh300]

@batsto

…but even then I just clean it with some windex and it’s like new again.

As an office supply dealer, I can attest that Windex ruins dry-erase boards.

The boards have a special coating that is somewhat non-porous that allows you to write on it without the ink soaking in and becoming permanent…at least, that’s how it’s supposed to work. If you leave the ink on there long enough, it turns hard, sort of like glue and it’s difficult to remove.

If you use windex or other glass cleaners (or acetone) you’ll remove the coating and end up with a board that’s very porous and will suck up the ink and then it will be impossible to remove.

Expo makes a dry-erase cleaner that dissolves the old ink without dissolving the coating on the board. It’s relatively inexpensive and if the board is taken care of and nobody leaves anything on the board for weeks at a time, it doesn’t have to be used often, and most importantly, you don’t have to use the whole gallon (it comes in the little 8 oz spray bottle and there’s also a 1 gallon refill for a few dollars more) to clean a large board. Usually if you spray a little bit of it, once you have the paper towel wet, it’ll keep working over a large area.