Linear Algebra
Fall 2016

Chalk and eraser notes

The white chalk I’m using is original Hagoromo Fulltouch, made in Japan. When it went out of production, I bought a lifetime supply. It is now produced in South Korea:

Hagoromo also makes colored chalk. I am trying it out again:

The colored chalk I’ve been using in recent years is made by Rikagaku:

I have a preference for Hagoromo white chalk, and a slight preference for Rikagaku colored chalk. However, the Hagoromo colored chalk spectrum is brighter (e.g. orange but no brown) and a bit thicker. I had hoped it would show better in these videos. In fact, other that yellow, it’s pretty hard to make out either colored chalk in these videos.

(It always amuses me when people grab colored chalk for body text on my office chalk board; it’s the same sort of design error as the common practice of using the font Palatino for body text in typesetting.)

The cloths I use for erasing are made of Korean microfiber; auto detailers consider these the best detailing towels made:

One can instead use applicator sponges, if one is stuck on the eraser form factor:

However, a towel offers far more surface area. I can teach two classes per towel, and I only need to wash my set of towels once a month.