(upbeat music) - The legend around this chalk is that it's impossible to write a false theorem. - I assume the special ingredient was angel tears. - Mathematicians from all of the top schools very frequently use it.
- It's a cult favorite. - As soon as I use it I was a convert. - The chalk is one of the best kept secrets in the math world.
- It's the Rolls Royce of chalk. (gentle music) (chalk scratching) - Hagoromo is a brand of Japanese chalk. The way it flows on a board is a bit hard to describe in words.
- It's really hard to get. You can only get it from Japan, you need a Japanese person to bring it back for you. - I discovered it when I went to visit the University of Tokyo and one of the professors there said to me, you know, we have better chalk than you do in the States and I said, oh go on, chalk is chalk.
And so I tried it out, and I was surprised to find that he was right. - I tried it, and I thought it was phenomenal. It's the densest, it erases the cleanest, it leaves the nicest line.
- If you use bad chalk often you have to press really hard for anyone to see what you're writing so using Hagoromo on a good board, it doesn't really feel like you're working hard to write. - When I'm teaching I get a feeling of energy, confidence, and the chalk absolutely helps. (chalk clacking) - Slowly the math world has become aware of this, and it became a bit of a fad in some circles.
(upbeat music) - It was like maybe four years ago the word came out that the company was going out of business. I sort of jokingly referred to it as a chalk apocalypse. So I immediately started hoarding up as much as I could.
- I ordered three boxes of Hagoromo and kept it in my office and used it very sparingly. - I should've bought more but I have friends that bought boxes and boxes and boxes of the stuff. They might very well be set for the rest of their career.
- We've got like 1,500 sticks. That's a lot of days, four sticks a day. I think I'm gonna make it.
- I have probably a 10-year supply still at home. - I calculated how many boxes would I need to last for 10 or 15 years. I didn't wanna become a chalk dealer, but I did like the idea that I could be the first stick is free chalk dealer on the block in my department.
- I was probably selling it regularly to maybe eight to 10 colleagues. I would reach into my cupboard in my office and pull out another box and we'd do the deal in my office. Yeah, we all had a chalk fix.
And we still do. (gentle music) - The original Hagoromo chalk is slowly disappearing. A few years ago, a Korean company bought their formulas and did the best job of faithfully reproducing it in Korea.
- It was mixed emotions. I was happy to know that it would still be made. But I was a little disappointed that I was less clever than I thought I was.
(gentle music) - In many ways mathematics is like craftsmanship, in some ways it's like artistry; in some ways it's like science. But there's a real high craft side to getting a beautiful lecture on a blackboard. Mathematicians admire this in each other and like to use the best tools for it.
- There's incredible value to this but the value is in using it up, not hoarding it.
