Yesterday's Star Tribune has a front page article on the University's steady abandonment of blackboards.

When Prof. Lawrence Gray enters a math classroom at the University of Minnesota, his teaching tools are his brain and a stick of chalk.
He stands at a blackboard and chalk flies over the smooth black surface, spreading strings of equations like weeds. He turns and gestures to his class, taps the board with the chalk for emphasis, swipes a spot clean with an eraser and races on.
Replace Gray's blackboards with whiteboards or, worse, a tablet computer that projects numbers onto a screen, and you might as well tie his arms or gag him. He's among an army of professors who want to keep their blackboards despite the university's push to eliminate flying chalk dust that can foil today's expensive classroom technology.

Eh. I don't have a lot of sympathy. There is a tactile difference to chalk and dry erase markers, but I think it's largely more a matter of familiarity and personal comfort and obstinate resistance to change that's fueling the opposition, not anything necessary to teaching. And math in particular—it's strings of symbols on a surface. Dry erase markers produce higher contrast, bolder lines; I would think that they would be superior to chalk, once the instructor gets used to them. I can use either, and tend to favor video projection, anyway.

Although…there is one place where I would favor the chalkboard. One of my pleasantest memories of my undergraduate education was my comparative anatomy course. I and many of my fellow students would always show up early for class, because Professor Snider would come in 10 or 15 minutes before it started, armed with his own personal box of colored chalk. And then he would start drawing. He'd sketch in these elaborate diagrams—skull bones of reptiles, birds and mammals, a hindlimb with the muscles pulled apart to show their attachments, a time-series of kidney development. One thing you can do with chalk that is impossible to do well with a dry erase marker is shading, and he'd carefully color-code all the parts he was planning to talk about that day. It was like watching a good sidewalk artist at work. And all of us students would be sitting at our desks with our collections of colored pens and pencils, filling in the pages of our notebook before he started talking, because we knew that once he started explaining things there wouldn't be time to draw.

And at the end of class, he'd take an eraser and quickly destroy all of his work. It was a marvel. The ability to blithely obliterate a beautiful creation because one can create it quickly and at will is a real talent.

There aren't many people around who do that kind of thing anymore, but I'd be willing to fight for the retention of blackboards to protect them.

The other thing he did that I'm really trying to work towards is that he would only have at most a half-dozen of these diagrams on the chalkboard, and that would be his whole lecture, taking apart and explaining each one in depth. In these days of easy, instantaneous page flipping with computers and video projectors, I'll easily zip through 20 diagrams in the same amount of time. I don't think I'm teaching better for it, though, and it's always a struggle between teaching students one thing very, very well or teaching them a dozen things rather more superficially…which you would think should be a no-brainer decision (depth of understanding is always to be desired!), except that I've got a list of a thousand things I'd like them to leave the class knowing, and chopping it down to a dozen is painful enough.