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Chalking the Talk

Writer's picture: Mishkat BhattacharyaMishkat Bhattacharya

This post was inspired by discussions with my colleague Dr. Vivek Narayanan, following my last post on giving physics talks. Below, I will discuss various aspects of teaching/giving presentations on a blackboard, using chalk. Read on to find if the chalk talk is truly outdated, or is fashionable as retro, or has new incarnations.


Technology


The writing is done with chalk on slate. White chalk is calcium carbonate (derived from limestone). Colored chalk is calcium sulphate (derived from gypsum). Famous chalk deposits in the world include the cliffs of Dover in England; there are substantial sources in the midwestern United States as well.


Slate is a rock formed from clay or volcanic ash. It is usually black, but can also take on other colors, like green and purple. Slate is found in Spain, China, Brazil, Maine and Pennsylvania. among other places.


Note: While researching this post I found that slate - scraped with an appropriate wooden tool - is used to mimic calls for turkey hunting. This video shows the amazing mimicry generated by the process.


History


The earliest usage of the chalk and slate writing technique I could track were in the fourteenth century. By the nineteenth century the technique was being used extensively for education. I remember using a portable slateboard as a child in the mid-to-late seventies. I recall blackboards being used in academia in a major way until the mid-nineties; in several cases, they are still in usage.


Pros


i) Chalk talks allow for building up the topic gradually, instead of distracting from the speaker's delivery with images and information that show up (mostly) all at once on the slide.


See this article for the benefits (contains an image of the famous John Wheeler giving a talk with colored chalk diagrams on the board).


ii) Chalk talking forces the speaker to pace themselves and the audience to fully participate in the rituals of note-taking and question-asking.

iii) Chalk allows for erasure, to accommodate mistakes or updates.

iv) Chalk is more biodegradable than whiteboard markers.


Cons


i) Chalk talks cannot show extensive data, simulations, or images of experimental apparatus.

ii) Some people consider chalk to be a pollutant. Chalk dust gets into the respiratory system, hair, skin, eyes and clothes. I have a dust allergy, and chalk often makes me sneeze. I recently tried using Chalk advertised as Dust Free: the sneezes were still coming.

iii) Chalk is fragile. Children often drop and break chalk. Snapping chalk on the board in mid-word is not a pleasant sensation.

iv) If held incorrectly against the blackboard, chalk can lead to an unpleasant screeching sound.

v) Chalk can be used as a weapon. I fondly remember many 'chalk-fights' at school, where all the students were throwing chalk bits at each other. Depending on where you get hit, chalk can sting quite a bit.


Modern Versions


i) Rolling blackboards: Most chalk talks do not allow us to 'go back to the previous slide', but some rolling blackboards do (a more substantial example, with a famous professor; the first board transition comes around 14:08).


Of course, today's technology would allow audience members to take photographs of each board before it is erased (students in my office often take cell phone images of the whiteboard at the end of our meetings). In some cases, the whole talk is video recorded.


ii) Transparency slides: A long time ago (the mid-nineties) I saw speakers writing on transparency slides for overhead projectors. Writing on paper and projection in real time is also a current practice; I have used it in teaching freshman classes.


iii) Whiteboards: These are now more the norm, with markers of various colors and some form of a microfiber cloth or pad for erasure, with some spirit-based cleaner often having to be used.


Still more modern digital equivalents exists today in the form of


iv) Tablet laptops (which I used fairly successfully, I would say, for teaching Modern Physics). These are quite advanced: one can choose the page format (ruled or blank; background color), font in case you need to add type; stylus thickness, scroll back if there are questions, insert extra information by creating space between previous content, cut and paste links and figures, use a palette to draw relevant geometric shapes such as circles and squares, and save, for posting later, the entire presentation as a pdf.


v) Light boards: These use glass boards, and some image reflection software. the display quality is quite striking and involves the presenter quite centrally.


vi) Smart boards: These digital gizmos are quite magical. Great technology and educational design, in my opinion. Check out the pen tray in the linked video, which provides chalk capability even if the pens go missing. Of course, the price tag for these widgets is higher than for the other options mentioned above.


Conclusion


Chalk-on-slate is an elegant and time-honored presentation technology which offers several advantages; more modern versions, once they are affordable, are what excite me, and what I would recommend. Of course, once in a while I enjoy an old style talk too.

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