CNN is doing a short web video on this chalk, and I was interviewed last week. They particularly liked my custom attache case for carrying all my colors to teach. When I drew diagrams revealing Catalan number correspondences, they were quite worried that these pictures "weren't math" and I might be hoodwinking them.
The "eraser" is a side category that doesn't get enough attention. At MSRI one uses auto detailing "applicator sponges" which choke pretty quickly with chalk dust, but are nevertheless superior to traditional erasers. Far better is a supply of auto detailing towels; here, Korean microfiber is unrivaled. For classes late in the day, I use one wet to wash the boards, then a dry one to erase as I work. When I run out I do laundry; these towels are indestructible.
So why use the sponges in a public setting? We're learning that animals in many particular tasks exceed human intelligence; it's a matter of each creature's focus of attention. Mathematicians like to believe that we're smarter than average, but we're actually just very focused. That can make us pretty dumb away from our focus of attention. A nervous mathematician giving a public lecture is unlikely to recognize what a towel is for, but a sponge has the right form factor. It's like making your modern heating in a bed and breakfast look like fireplace logs, to not confuse the customers.
I too am enamored with Hagoromo; however, I wasn't able to get any of the Japanese chalk. I have been using the South Korean produced Hagoromo and find it quite nice. How do you think the Japanese vs. South Korean produced chalks compare?
Good note about the microfiber! I'll have to try that. I've become increasingly frustrated with erasers. When it comes to washing the board, do you use a squeegee at all? I've found a sponge/squeegee combo to make cleaning quick.
A dimension of chalk usage that seems to be missing from your page - what do you think of chucks (holders)? Hagoromo chalk is quite wide (11mm) and it seems that most chalk holders are built for 9mm chalk. I use the Hagoromo branch chalk holders, they seem to have good grip. The other alternative I've found is to look for artist-oriented graphite or pastel holders.
I used to carry a bucket and sponge, then a squeegee, spray bottle, and paper towels. Now I just use a damp detailing towel (not wet enough to drip), and water from the nearest source down the hall. Sometimes one needs to clean the towel and make a second pass to obtain a board that looks newly installed, but generally no squeegee is needed.
Wrong person to ask about holders. I like gripping bare chalk; my hand is too forceful for a holder.
It doesn't necessarily. One thing that can come with ADHD is hyperfocus for certain activities. If one has ADHD and an intense interest in mathematics, you might be in luck.
When I was in school, I have a hard time staying engaged in lecture, and homework was near-impossible. I got a C in physics, but set the curve on the tests. It was a fascinating topic, but I couldn't stay focused on the bookwork.
Occasionally I will find a project that fully engages hyperfocus, and it's incredibly satisfying. I once fabricated a motorcycle carrier in a day and a half, pausing only to eat and sleep.
I successfully completed an Applied Math masters and defended a dissertation on symplectic integration. But that didn’t quite give me the superpowers my professors had.
I'd be surprised if you get five seconds on the final video. You might also be edited out in a way to make it look like you said something other than what you intended to convey. The Catalan diagrams will almost certainly not make the cut.
We'll see! From my experiences with reporters after being the math consultant for "A Beautiful Mind", I share your cynicism. This crew nevertheless impressed me. They'll certainly open with a closeup of my chalk attache case. The Catalan diagrams just didn't fit the prejudices that she imagines of her audience. I was interviewed with these diagrams behind me, so it will be hard to use anything I said without them appearing past my ear.
You taught me Linear Algebra back in 2013/2014 and I remember you were telling us about this amazing Japanese chalk you were using.
To your credit it was quite good, and produced some really great writing. I wished my other math professors had your passion. Half the time I could barely see the writing on the board after the first erasing.
Thanks for the infomation, I don't think I have seen anything except Linex chalk while I have been at university in Denmark. So it is interesting that there is people who uses a specific type of chalk.
I studied physics and this at a time when faculty gradually changed from blackboard-based lectures to powerpoint. The blackboard-based lectures were far superior to any other way of lecturing (in my view).
Main benefit was in the speed of presentation. Writing on a blackboard takes some time, the lecturer is slow enough in presenting that you can really follow along, while not "standing still". What a contrast to powerpoint presentations where the lecturer paused for a minute or two to let students read the equations. Either time was not enough, or you'd start to get bored.
Until I graduated at the end of my 5 year program, I tutored freshmen students. Towards the end of my time at uni, they almost exclusively had lectures with powerpoints. I sat in one of the into lectures and what had been a good introductory course to classical mechanics had turned into a mind-numbing powerpoint karaoke show.
I find another benefit of blackboard presentation is the order of information. The lecturer can build something up rather than simply showing the finished article and saying voila.
Working a project on a blackboard also encourages people to get the order right. It's surprisingly common to see Powerpoints which skip or reorder steps completely because the slide creator shuffled things around or worked backwards from the answer.
I'm sure most people have seen professors skip numerous steps on blackboards, too, but in my experience there's at least a heightened awareness of what it looks like to actually work through the problem.
What's best about black/whiteboards for me is precisely the nonlinearity. Numerous times I've seen professors realize near step 10 of the proof that something they said in step 3 isn't quite right; then a sidebar is opened and arrows start to be drawn to piece the puzzle together.
The point of going to classes versus studying alone at home is that you get to watch mathematicians doing mathematics. It's apprenticeship learning, the same as carpentry. Watching the professor reason and make mistakes and second-guess himself is invaluable. The typed class notes where everything is neat and theorems are numbered gives the impression of an immaculate birth that the student can't fathom arriving at. The best maths classes are the ones that teach you how to be a mathematician.
This is a much better expression of what's great about chalkboards than just the order of steps, thank you. It's not so much seeing a problem worked out in sequence as seeing it worked out for real. Even if the professor is working from lecture notes with all the steps, writing them out live engages with the content in a way that pressing "next bullet" doesn't. And as you said, what's missing is the messiness - catching mistakes in the notes, making mistakes on the board and finding them, puzzling over what belonged at a missing step.
Everyone jokes about the frustration of copying a full blackboard worth of notes and then having the professor go "wait no, that wasn't right" (myself included) but it's a valuable experience. That moment of "hm, hold on a second" is where the math is happening, and a chalkboard helps professors and students notice that. (And of course, when something "isn't quite right" on the Powerpoint, it's a tremendous pain to fix...)
A great teacher will be a great teacher with whatever you give them. But anyone not 100% tuned to that part of their teaching greatly benefits from some of the constraints that chalk gives them.
I'm a K-12 admin and once we had a HS teacher who was brilliant but her classes were often too difficult to follow for the kids. We just told her she couldn't use the powerpoint slides anymore. Yes, there was a huge discussion of timing and pedagogy and all of that, but ultimately, placing that constraint on her naturally put her at a much more equal footing to the students she was trying to teach.
When you try to force could behavior by handciapping people, you also get utter failures like teachers with bad (or too-slow) handwriting who cannot succeed at conveying information via the arbitrary restriction.
I think it's even better if the slides are posted prior to the lecture so that interested students can make their notes annotations on the slides - this allows them to fill in trouble spots while not having to copy down all the material (I find it distracting to try to rush to copy everything down, personally).
As someone in college who has had their classes recorded and posted online, I still go to class because its dedicated time to my brain. There is nothing else I should be doing other than being in class.
The people who don't show up would have not showed up class recorded or not. It is very useful though when you have a morning class miss or be dead tired and not pay attention to re-watch the lecture to get a better understanding.
It seems like whatever recording either I or the professor make are actually useful to me later on. It's always the classes I don't record are the ones I always need.
If no one goes to the physical classroom why not sell the same recorded lecture to a thousand people online instead of the 100 that fit into a classroom?
I had a world history/geography/current events kind of class in college that had an in-person lecture and was also livestreamed and recorded. Lecture hall fit about 1800 people but he also had an unlimited class size "online" section you could sign up for if you didn't get in-person section during early course request. You never actually had to go to class. The professor had to get his own system for taking quizes and handing in assignments since the online learning management system the school used would choke with that many students at once trying to submit things.
Content aside, it was a very interestingly run course. Assignments were at your own pace, you had a large list of the kinds of projects you could turn in for credit. There were quizzes, exams, essay topics, interview topics, and an option for independent projects to get credit. Each kind of project had it's own maximum point value it would be graded out of and the final grade was totally based on how many points your actually earned, not out of how many. Even if you did a shit job on every assignment, as long as you did enough of them, you could get an A. It was a nice way to boost the GPA from just sheer effort rather than actual achievement.
> Main benefit was in the speed of presentation. Writing on a blackboard takes some time, the lecturer is slow enough in presenting that you can really follow along, while not "standing still".
While I love chalk, and miss it since my current university uses whiteboards (actually stupid @#@#* WallTalkers, despite our pleas), it's hardly the case that the two options are 'chalk' or 'Powerpoint'. Also, Powerpoint slides can be delivered at a reasonable pace—I've seen many professors fruitfully use slides with blanks, distributed to the students in advance, on which students can take notes—and chalk-and-talk lectures are scarcely universal models of pacing—one 'remedy' often pursued by lecturers who want to go faster than they can write is just not to write anything.
In EE blackboards were mostly replaced shortly before / while I was there a few years ago. Whiteboards are _vastly_ inferior for two reasons in my view:
1. Colours are harder to distinguish, or to see at all. Chalk is easy, even a brand new pen is difficult from more than a few rows back, possibly made worse by my colour blindness;
2. You can't go over an existing pen line. You can _sort of_ make it thicker (but typically remove part of it at the same time) but you can't draw a square and then go over one edge in red, for example.
I once had a professor that would write on the blackboard with his right hand and erase with his left simultaneously. Quite a struggle to keep up with equations on those days he chose to fly through lectures like that!
I feel like some things work on powerpoints and other onthe blackboard, for example maths work a lot better on blackboard. Some of our best lecturers had a powerpoint but they first showed the equations on them after they had showed them on the blackboard, which I found pretty good.
When did this happen? I got my PhD in physics in 2008 and other than the introductory undergrad classes, all other classes (that I knew of, at least) were still taught using chalkboard/whiteboards.
And I agree with a sibling comment on this thread. The speed of information is ideal with live ‘writing/derivation’, as you can follow along at the teacher’s own pace and write each step yourself.
I used to do his for my own section classes I taught as a TA. I’d come in with a small post-it size note of starting points, and just work brought problems without referencing anything else. Kept it down to Earth, and I think (or hope) showed the students there’s nothing insanely hard here, just lots of small bite-sized steps.
Personally I find it is the responsiveness that is the real benefit with a good professor - they can respond and go off into areas a power point slide would not be prepared for. Ultimately the worth of a tool is in how it is used.
Hands-down, the best presentation and note-taking math class I recall in college (discrete mathematics, a graph theory course, heavy on drawings) was run through a Wacom pen display on the lectern, linked to a projector. The professor could accurately and cleanly draw the required notation with his hand flat. Why erase when space is infinite, just scroll and/or zoom in the desired direction. A full color spectrum was available. If something needed a chart or other graphic to better explain, that was a swipe away. And the output of the lecture was always available after class, so you could take notes on the important parts or follow-up questions, instead of having to try to scratch everything he narrated as fast as he could speak and write. It just made so much sense.
That sounds similar to the approach my Prealgebra teacher used in 1994. She had an overhead projector with a roll of plastic transparency sheet attached. She wrote across the bottom of the projector and then rolled it up as she went along. Different color pens were available. You could follow along and understand the process, and there was plenty of time to take notes as the material rolled up the screen.
I think that all of my math teachers in middle and high school used projectors with transparencies. It wasn't until college that most math and physics was on black boards. The major benefit of transparencies is that the teacher was always facing the class. So they could just look up to make eye contact with students.
I hadn't given it thought before, but I assume transparencies weren't as present in college because the room a given college class will be is essentially random. It's not an environment controlled by the person teaching. in high school and middle school, that was the teachers' classroom. The teacher stayed in their room, and we moved around. Projectors require more maintenance (bulbs going out!), and the college teachers would need to lug around their transparencies and pens. But all college classrooms have blackboards and some chalk.
Overhead projectors require a fairly dark room, and only work well up to a certain size and distance. Much beyond that, their light gets too dim, and if it is a large lecture hall, you need a large projection with very bright light for everyone to see.
Then there's off-axis people who might find a projector difficult to read. In a small classroom, both of these issues don't really come into play.
A blackboard, however, can be seen in a brightly lit room, almost anywhere in the room, even if the room is very large. For the really massive size lecture halls, you can have multiple blackboards that span the width of the room, plus sliding and portable ones.
Each system has its benefits and detriments I guess...
> large lecture hall, you need a large projection with very bright light for everyone to see.
And the hard limit on how bright you can make that is that the lecturer is staring into that light while writing so you can only make it so bright before it becomes painful or damaging. Anecdotally when I was in elementary/middle school we'd sometimes have to work things out writing on a projector and it was tough sometimes and looking up you couldn't really see because your eyes had adjusted to the brightness of the projector. Maybe they could improve the lenses to spill less light out but it wasn't back then.
Absolutely true, and I didn't think about this. In retrospect, my intro physics courses (which were 90% engineers) were in such classrooms, and could not have used a projector. But the rest of my physics classes, and all of my math classes, were in rooms the size of my high school classrooms.
Huh, this sounds almost exactly like my experience too, down to the same year and subject! This was in Mexico, but our teacher was from the southern US, I believe. I wonder if it was a particularly popular teaching method of that year.
We had a lecturer who tried this with an early tablet computer (c2005) and IIRC, onenote. He got about two or three lines of equations on the screen at once before scrolling it off the top, so there was none of the ability to slow down, comprehend, then quick transcription that moving onto multiple blackboards allowed.
Having the last 10 minutes of progress, or more in special lecture theatres - allowed cross-referencing and observation that is hard to replicate with pre-prepared slides or with a single window of view.
Massimo Gobbino from Università di Pisa has been using this method for a while, he puts both recordings and notes online for everyone to learn from [0]. It's all in Italian though. It'd be amazing if this was done by more people around the world.
I had one lecturer in my 4 years at university that only used a chalkboard, and most pupils despised him because the pace as which he wrote far surpassed the rate at we we could sensibly copy notes. We wrote it out, but it gave little time to actually consider the concept we were learning. The rest of my lecturers all used PowerPoint presentations for the most part, in conjunction with print-outs so we could follow along on a projector and write notes/annotations on the provided sheets.
In my eyes, a hand-out + computer notes (which can later be emailed to the pupils) is by far the superior teaching method for most students. This is of course just personal preference, but I much prefer simply sitting and listening to the teacher while occasionally asking questions - taking in as much as I can, then copying up the notes later using material provided by the lecturer so as to commit it to memory. Frantically writing out the notes during the lecture, then going home and trying to eek out some sort of understanding from them just never sat well with me.
The optimal teaching approach may depend on the level of the material, too. Slides & notes mailed to students may be a great option for "routine" math courses, things taken by a ton of different majors, where the paths are ground so smooth by the millions of feet traveling it that the entire class can be called in advance by even a fairly green instructor, almost down to the questions they're going to get.
As you get into higher math, though, the chalkboard becomes more important, because it's a lot more like working it out in front of the student. The class is far more likely to ask questions that are going to consume a couple of boards of scribbles to answer, and the professor may not be able to anticipate it all in advance. Trying to do this on a slide is very inconvenient and I'm still yet to see a computer interface in common use that can pull it off at all.
Many of those classes I took were actually hybrid; there was a core set of projected slides that could be mailed out (though they weren't always) that set the agenda and gave the basics and results, but there was a lot of chalkboard use as well, since as long as the room is even modestly large, there's no particular need to use just one or the other.
Graduate-level graph theory in particular used the chalkboard pretty heavily for what were essentially impromptu animations, between the numbers being added to a diagram as whatever algorithm we were learning about progressed, and the gestures being used by the professor.
That certainly makes much more sense. My experience was primarily undergraduate, plus a years masters. I will admit, during the MSc chalk-board work was valuable during the seminars and labs, where it was much more design based.
I found the exact opposite when learning math. I need to write it down, and when presented with Power Point I have to transform it into something I can understand, and that means I don't have enough attention left to really listen to the lecturer.
On the other hand, the lecturers that used a blackboard at my uni all had prepared the lecture, what they wrote was meant to be written in a notebook. They wrote it at a pace that could easily be followed. This allowed me to go over proofs as I wrote them down, and I could then ask right away if there was anything unclear.
I also found several typos (usually a sign error or a missing term) this way, something which would probably have confused me a lot if I didn't catch it until I got home.
So, for me, well-prepared blackboard lectures is preferable, at least for math heavy stuff.
I also need to write it down, but not immediately upon hearing it per-se. I find that when I write, I often zone out and leave my muscle memory and a slight sub-consciousness to do the work - nothing actually goes in. If I just listen, it forces me to focus and it gives me time to build a framework of the concept in my head, that I can fill in later. I suppose it's similar to the methodology used in "How to Read a Book: The Ultimate Guide" by Mortimer Adler. He uses 4 steps-
The first 2-3 are covered in the lecture. The time at home can then be spent putting it to paper, applying it in practice (usually in MatLab or some other form of programming), then summarising. That's why I like the lecturers electronic hand-outs, as it can fill the gaps of knowledge that have formed between lecture and study. My background is in EE however, so assumedly this type of learning might not apply as well to pure Math/Physics!
Shouldn't you be paying full attention instead of taking redundant dictation during lecture?
If you weren't stuck with following a chalkboard, typos could be fixed once and for all time at the source, instead of reappearing at random in every lecture.
But that's the point, I was paying full attention. By writing things down, I had time to process and think about what I wrote. I had time to fully follow the derivations. And that's in addition to the reinforcement effect that the act of writing has (at least for me).
Merely sitting there passively listening would not be paying full attention.
Of course, this required the lecturers to write in a suitable tempo.
As a TA when I was up there it felt like it was taking forever and that I might be losing peoples attention which forced me to speed up (likely making more mistakes and making it less legible to boot).
In this day and age why not pay attention to what the prof is saying, take scarce notes and use a phone to take a snapshot of the blackboard and rewrite it later for better comprehension. One could also use audio or even video.
The act of taking notes is where at least half the value of notes are. Review latter is useful, but you can review the book. I cannot read my own writing, I still find I learn better when I take notes.
For the better, take notes afterwards while listening to a recording and looking at the blackboard snapshots. However, I understand that this cannot be a regular practice due to time constraints but maybe this could be used for the classes that spark most interest, the knowledge crystallizes better with a few passes
I'm not sure if that is actually better. I seem to recall (but can't be bothered to look up) a study that showed students who read the book twice do no better that those who read it once. Which is to say the first time you see material in some format is when you get the greatest gain. Taking notes the second time through probably isn't worth it, though taking notes from a different source of the same material might be.
I personally used this practice and it helped me tremendously. It freed me from following the blackboard word by word and let me take briefer notes, sometimes incomplete, only to return and redo all the notes comprehensively. It felt like take attending the course twice. However, I only did this for the classes that I was very interested in. For all the others it can easily turn into a waste of time.
You are speculating without justification. Re-reading having no/lesser benefit (a highly-suspect conclusion, given the massive sucess of spaced repetition), says nothing of the benefit of reading once + writing once.
Recording and retaking the notes from the audio/snapshot is actually reinforcing the knowledge twofold, one is recalling the info and then rewriting it. I don't know if this is for everyone (most likely not) but it did work well for me.
Many of us did just that, and we had one classmate who recorded the lecture using a high-def camera to replay later, but all it took was one difficult to read segment and the notes became illegible. The lecturer also got incredibly aggravated when people didn't write notes, which didn't help matters also.
A lot of people, myself included, commit things to memory through writing. A lot of good lectures go beyond the books, so content can easily be forgotten. I even took notes while reading the books, lest I forget what I read.
Porcelain whiteboards are, in my opinion, far superior to chalk. Color, distinct lines, easy to clean with just water (completely with no marks). Those who complain about whiteboards usually are only familiar with melamine boards.
I got a big porcelain board for 5 bucks on eBay because one corner was dented. Best purchase of my life.
There are huge quality differences in both whiteboards and blackboards.
It's not a lack of familiarity with melamine boards, it's acute familiarity with incompetent penny-pinching marker supplies. Most public whiteboard lectures involve the search for markers that aren't dry; the organizer might as well be standing there in their whitey-tighties.
Of course, Universities rarely provide Hagoromo chalk, and those of us reading this would also be bringing our own markers to any whiteboard lecture. So if faced with whiteboard conversion, we should speak up for melamine.
Still, I imagine that in five hundred years there will still be Steinway grand pianos, and some people will still prefer sex in person, and some people will prefer using actual blackboards. A whiteboard reminds me of that humiliating scene in "La La Land" where Ryan Gosling plays a solo one-handed on a toy electric piano.
> I got a big porcelain board for 5 bucks on eBay because one corner was dented. Best purchase of my life.
In case you or others aren't aware:
Bathroom tile backer board is commonly sold at big-box home improvement centers for a very low price per 4x8 foot sheet of material. It's the exact same stuff as commonly sold whiteboards, just without the aluminum edging and large price.
I've worked at a couple of employers who had open-plan style work areas, with the walls lined with such boards. Everyone had a set of white-board markers and a rag or eraser, and maybe some windex.
It's a cheap and practical solution for brainstorming and other uses software engineers often find themselves involved in.
The problem I have with whiteboards, and especially porcelain ones, is that they are too slippery. Writing on a chalkboard offers a certain amount of resistance and texture that just feels better than on a whiteboard. This is also something that you really need a high-quality board to experience. The texture of cheap chalkboards is not very pleasant either.
I have experienced this but only when it’s wet. The tricky thing is that it seems impossible to dry it completely with anything but time. So you do need to wait a good few hours after cleaning with water.
As a couple of commenters noted, a Korean company (Sejongmall) purchased some of the machinery, adopted the Hagoromo Fulltouch brand name, and recently started producing and selling chalk. You can buy it on Amazon, for example.
In my opinion (which seems to mostly be shared by other mathematicians), the quality is quite good -- approximately comparable to the Japanese original. Also the price is cheaper, $17.00 for a 72-piece box.
We chalk snobs have breathed a collective sigh of relief.
The affiliate link at the end points to a $139.99 version of the chalk box on Amazon, when an identical box next to that amazon listing shows at $17. The article came out in 2015, so seller or amazon or both are possibly scalping the demand while the article publisher seems to also profit.
Mirroring some other comments here, my best experiences were with overhead projectors and document cameras. My high school math teacher would sit on his desk at the front of the classroom and use an overhead projector with transparencies on a roll so he could just roll up as he wrote. In college a lot of professors used document cameras for basically the same approach. I think it was by far the most effective way to teach math because they could just write equations etc. out and also face the class, and they didn't have to deal with chalk or dry erase markers.
The soothing sound of the overhead projector, the dim light of the classroom combined with both the subject and the relaxing voice of the teacher were unbeatable for mid-day sleep during college.
I studied under Brian Conrad. He could write on the blackboard faster than I could take notes, and his lectures were elegant and well-thought-out, if abnormally fast.
Glad to hear that he's cornered the market on quality chalk!
I prefer high-quality markers and whiteboards. As for "toxic cleaning chemicals," you can use your own recipe to make a mild cleaning solution. Far less toxic than lifetime exposure to chalk dust.
This reminds me some of what I've read about Blackwing pencils (originally made by Eberhard Faber Company), which were discontinued in 1998. The originals (NOS) were apparently quite sought after once production ceased. California Cedar Products is now making a "Blackwing" pencil[0] which purports to be the "revival", but there is some criticism[e.g., 1].
I have never used an original Blackwing, so I cannot comment on those, but the new ones are enjoyable to write with. It's similar to the feeling I have when using fountain pens – they're such an improvement for the act of writing that I actively seek out reasons to hand-write things.
The specifics of this chalk story versus the Blackwing story are different, but it's neat to see the passion people have for their writing implements. And that many of these, admittedly higher-quality, versions seem to be unable to survive the decrease in hand-written forms.
As for me, I do prefer chalk to whiteboards. I've always been slightly annoyed at getting chalk on my hands and so think I would have enjoyed using this chalk if I'd had the opportunity. But I see fewer and fewer chalkboards around.
I'm not sure why we thought chalk boards needed replacing.
White boards seem generally inferior, and even worse is this newer trend of large computer based boards.
The college I went to had a mix of whiteboards and chalkboards. Even as a student I preferred the rooms with chalkboards. It seemed like the light on dark contrast and no glare made them easier to see.
I also find disposable markers to be a bit of an environmental horror. In the grand scheme of things maybe it's not that much waste, but replacing something like chalk with a thick plastic non-recycleable marker for little if any gain is disturbing.
This reminds me of a story I read about 10 years ago of a Japanese manufacturer of a very specific type and format of scientific lab notebook that ended production. I think about the story every now and then and go on a deep dive, but can never find it. Buried in the web.
Do the manufacturers of this chalk (or any chalk) regularly test for asbestos contamination?
From what I understand, it is kinda the same safety hazard you'd have with cosmetic uses of talc (for makeup and the like); the risk is low for contamination, but it is possible - which is why they do testing on talc (and even then, there is still the possibility of it being present in very, very low amounts).
I could understand how chalk has a romantic aspect to it, compared to whiteboards. It conjures dusty libraries and hardwood desks. And I think such things have a larger impact on abstract thought than many appreciate.
But I definitely can't imagine replacing either with PowerPoint, of all things.
> “Maintaining a clean whiteboard is much more of a pain,” he said. There’s the cleaning fluid, which costs money, and the chemicals can cause health problems.
A clean blackboard is not that fun either. To clean it nicely you need to sweep the whole of it down vertically with a wet sponge. This requires a water source and it's a messy deal. In high-school there was a daily designated pupil who was responsible for wiping down the boards and keeping a wet clean sponge.
When I was studying physics, I had a calculus professor who was popular among students for his good use of the blackboard. He would write a ton of text (about 20-25 sqm per 90-minute lecture), but everything was really tidy and well-organized. (He held the same lectures that he gave for the last 20 years, so I guess he got some insane amount of gradient descent going on over time.)
Anyway, for the cleaning, he had a flat mop. The lecture hall had three separate boards, so he used them in rotation. When he was finished filling board A with text, he would wipe board B with his mop while recapping the contents of board A. Then he would rinse the mop and leave it in the sink next to the boards. At this point, board C had dried enough from the previous round of cleaning that he could start writing there again.
Overall, an incredibly efficient and fluent process. The gap in writing gave the students enough time to finish copying everything in their notes or taking a short break to drink something, and it gave him enough time to recap the last 10 minutes before moving on to the next section.
>He held the same lectures that he gave for the last 20 years, so I guess he got some insane amount of gradient descent going on over time
I took Calc 2 with a lecturer like this. She had been working there for a few eternities and could probably have taught the wall how to integrate. She had a reputation of being the "easy" professor but after comparing with other students it turned out she actually assigned substantially more work and covered the material faster. Her quality of teaching was just so highly refined that it made the work easier.
In Germany they outfit classrooms with sinks and squeegees.
Over decades I've tried absolutely everything. I see colleagues in earlier stages of evolution on this (e.g. carrying a squeegee and a bucket), but mathematicians are unbelievably stubborn (think zebra) so one learns not to say anything. This is like debating programming languages: If all parties haven't written significant projects in all languages under debate, just learn to walk away.
Wet or dry, nothing beats a Korean microfiber auto detailing cloth. One or two passes damp (not wet enough to drip while walking) will clean a board better than the overnight cleaning staff. Dry will erase better than any eraser.
In some (maybe most, but my experience is limited to a few) German university they have sinks, sponges and a thing to dry the blackboard after wiping it with a sponge in every class
It is definitely not just isopropyl alcohol. You can verify this yourself by looking at the MSDS. Whiteboards are non-porous, that's an essential part of how they function. The isopropyl alcohol degrades the non-porous layer on top and over time leads to ghosting.
I think it's sometimes a mix of several alcohols, but that probably has more to do with ethanol being cheaper than with any issue of suitability or effectiveness. Recently, I've also seen "cleaner" that's definitely not alcohol-based and also doesn't work worth a damn.
For questions like these, I would start with the MSDS. While the MSDS doesn't always answer your questions, they tend to be reasonably conservative relative to typical use. For example, they sometimes recommend safety gear that people ignore.
Keep in mind that isopropyl alcohol is available at different concentrations, and the different concentrations have different MSDS. Here are the hazard / precautionary statments from the MSDS:
H335 - May cause respiratory irritation
P261 - Avoid breathing mist, vapors, spray.
P271 - Use only outdoors or in a well-ventilated area.
Note that "avoid breathing mist, vapors, spray" is not an especially strong statement.
If I remember correctly, the three machines were sold off to different buyers. Regardless, it is probably far too early to be revived, even under the guise of nostalgia and perhaps too niche a product, say, compared to the Impossible project. Although not the same, there are alternatives available:
https://www.math.columbia.edu/~bayer/LinearAlgebra/Video/Cha...
CNN is doing a short web video on this chalk, and I was interviewed last week. They particularly liked my custom attache case for carrying all my colors to teach. When I drew diagrams revealing Catalan number correspondences, they were quite worried that these pictures "weren't math" and I might be hoodwinking them.
The "eraser" is a side category that doesn't get enough attention. At MSRI one uses auto detailing "applicator sponges" which choke pretty quickly with chalk dust, but are nevertheless superior to traditional erasers. Far better is a supply of auto detailing towels; here, Korean microfiber is unrivaled. For classes late in the day, I use one wet to wash the boards, then a dry one to erase as I work. When I run out I do laundry; these towels are indestructible.
So why use the sponges in a public setting? We're learning that animals in many particular tasks exceed human intelligence; it's a matter of each creature's focus of attention. Mathematicians like to believe that we're smarter than average, but we're actually just very focused. That can make us pretty dumb away from our focus of attention. A nervous mathematician giving a public lecture is unlikely to recognize what a towel is for, but a sponge has the right form factor. It's like making your modern heating in a bed and breakfast look like fireplace logs, to not confuse the customers.