One unexpected benefit of my recent trip to Berkeley, California was having the chance to meet the Coordinating Instructor of UCMAP’s Yongmudo program, Dr. Norman Link. My teacher and I watched an open dojang for his club for a while, and we enjoyed seeing the students train in this style that merges the striking techniques of TKD with grappling and joint manipulation techniques. Eventually Dr. Link came off the training mat, where he told us a few stories that were both entertaining and chock full of historical interest.
I’ll save those tales for another time, but I will mention one even more unexpected bonus from the trip. Later that evening, while I was unloading my stack of concrete bricks to break, Dr. Link approached me and asked, “You know about the correct weight for bricks, don’t you?”
I immediately thought to myself, Oh NO. . . what if I have the wrong bricks? Short of an Ocean’s Eleven style heist at a closed masonry supply yard, there’s no possible way to get more before I have to break them tomorrow morning!
“No,” I said, “I don’t know anything about brick standards.”
Dr. Link held up one finger, popped into the UCMAP office at the back of the dojang, and came back with a photocopied paper he’d published1 almost exactly twenty years ago. The title: “Choosing Brick Breaking Materials.”2
I couldn’t bear the thought of even reading this paper before my break attempt, because I didn’t want to know what it had to say. . . just in case. I tried my best to put it out of my mind. That said, I was overjoyed to see it, because it promised to address a theme I’d often wondered about: why do some bricks break on our school’s Dan level tests, while others are seemingly indestructible?
A few years ago, I’d actually talked to an engineer at the agency responsible for national concrete standards,3 and I did a little additional research to try to answer this question, but I became distracted by other things and never came up with a satisfactory answer. More recently, I considered asking a couple of our advanced students who work in relevant scientific fields (physics, kinesiology) if they had any interest in co-authoring a paper on this exact subject. Once again, other tasks took priority, and I never got to it.
After my break, I read the paper with great interest, and I found that Eureka! it was exactly the paper I’d long wanted to read—or, if necessary, write. I was thrilled to see it, because it meant I didn’t have to think up the methodology and do the work to gather the data. . . and I told Dr. Link so via email. Here, then, is a summary of the Links’ key conclusions, for the purposes of our school:
- The kind of concrete bricks we use on our tests and demonstrations (16″ x 8″ x 1 5/8″ wall capstones) should weigh less than 13.5 pounds, ideally closer to 12. With the size constant, weight gives a decent approximation of density, which is the most important factor in safe and successful breaking.
- Concrete takes a very long time to completely cure, so the longer it sits in a lumber yard (or in storage after purchase) the stronger it becomes. Heat is also a factor, so bricks should be bought from the freshest possible source and stored in a cool place for the shortest possible time.4
- If, for whatever reason, it’s not possible to weigh bricks before breaking them, it’s best to use bricks with a rough surface instead of a smooth, uniform surface. Like lighter bricks, these are more likely to have a lower density.
The above is a highly condensed summary of the paper’s findings, but the rest is well worth a read. The study is clear, thorough, and written in a highly readable style. It includes a diagram of the apparatus used to measure breaking force for dozens of bricks, scatter charts showing the data gathered during testing, and a cool story explaining some of the outlying results, i.e. a small number of bricks that required vastly more force to break than others that were visually identical.
If you’re interested in reading this paper, which shows that the breaking force for our standard bricks can range from just over 300 pounds to a daunting 1100 pounds (!) please let me know. I am attempting to locate a copy of the original monograph and would be happy to order one for you if I find a source. I’ll also update this post later if I find a link to an online version, an effort in which I have so far been unsuccessful.
1 Co-published with his wife, Susan Link, who is also a highly accomplished martial arts practitioner. Awesome!
2 Link, Susan and Link, Norman, “Choosing Brick Breaking Materials,” Martial Arts Monograph Volume 3, University of California IMARI, 1997.
3 A nice fellow—by the name of Mike Maroney, of the National Concrete Masonry Association—who was amused by and interested in my questions, but who ultimately wasn’t able to provide the same level of rigor found in the Links’ paper. This is not his fault. Having read the paper, I realize I wasn’t taking the right approach and asked Maroney the wrong questions.
4 Because our school is filled with beer connoisseurs, I can’t resist the analogy: consume bricks the same way you would a fine IPA.