I've spent time focusing on the best chalkboards and chalks on my tools page, but -until recently- I've not spent much time thinking about the last part of the process -- erasing. At the suggestion of several colleagues, I played around with several different methods of erasing chalk marks to find which is most effective. The results were decisive. This post outlines the results, and attempts to present a simple test as justification (though my own testing was more extensive).
Of the suggestions I was given, I decided to test the methods listed below. Felt erasers were what I had always used, and I think are the standard in many universities across the US. The sponge was an interesting suggestion, in that it has a similar form factor to conventional felt erasers. I was most skeptical of the microfiber towel suggestion. I thought it would feel weird to not have a handle to grab.
To demonstrate the differences between the methods, I drew a fair amount of horizontal lines in different colors (white, blue, yellow, and red). I divided the lines vertically into multiple columns; one column for each method. I took a few images after each pass.
A look at the tools pre-erasing, note that they are all chalk-free!
The board after a single pass with each tool. Notice how the felt eraser just smeared the existing lines, but they are still fully recognizable and distinguishable (bad). The sponge did a little better, but made a terrible noise while in contact with the board. Lastly, the microfiber towel surpassed my expectations and the other competitors, erasing nearly all trace of the lines in the first pass! Not only does the towel method erase better than the others, but it produces less dust as well.
The board after 5 passes with each tool. The felt eraser has closed the gap on the other methods, but still doesn't compare fully. The microfiber towel method:
A quick look at the tools post erasing. The felt eraser has gathered the chalk in highly-clustered places, whereas the microfiber towel has absorbed the chalk in a fairly uniform pattern. This latter observation explains why the towel continues to work well long after the eraser needs to be cleaned, there's a surface-area advantage!
An aside about cleaning up the tools: the microfiber towels are machine-washable (do not use softener, only dry on low or no heat). This is much easier than the felt erasers, which I either had to clap against eachother outdoors, or vacuum with a special nozzle on the vacuum cleaner.
Winner: Microfiber Towel! (I won't go back). If you prefer the form-factor of the felt eraser, wrap it in a microfiber towel!