# Clear boards?

**URL:** <https://boards.straightdope.com/t/clear-boards/345752>\
**Category:** Factual Questions\
**Created:** [February 23, 2006, 5:08am UTC](https://boards.straightdope.com/t/clear-boards/345752 "2006-02-23T05:08:12Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![seanlee](https://avatars.discourse-cdn.com/v4/letter/s/2bfe46/32.png) [@seanlee](https://boards.straightdope.com/u/seanlee)\
**Post date:** [February 23, 2006, 5:08am UTC](https://boards.straightdope.com/t/clear-boards/345752/1 "2006-02-23T05:08:12Z")

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Having grown up around, beside–and occasionally inside–televisions, I’ve seen my share of movies and commercials, many of which happen to deal with math. Whenever I catch the season’s hottest differentiating flick (“difs”), however, I have invariably found the following scenario played out: a slightly eccentric professor is standing in front of the class scrawling miles of equations… ON A CLEAR BOARD. A CLEAR BOARD! A CLEAR…ahhh, you get it. This is driving me crazy. No one has been able to provide a satisfactory response to the following questions:

- What is this clear material?
- What does one use to write on it? (e.g. dry-erase markers, grease pencil, mascara…)
- Why does it have to be clear? Are there any distinct advantages a transparent board has over a white board or the classic chalkboard?
- Is this board actually used outside of Hollywood? If so, why is it exclusive to science and mathematics instructors?
- …and… uh… what is the cost of this material, say, per sq. foot? Or panel. Whatever they sell these things by… (cubits?)

I’m losing weight. I can’t sleep at night. My friends and family say I’m starting to withdraw.

Please advise.

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**Author:** ![TJdude825](https://avatars.discourse-cdn.com/v4/letter/t/dec6dc/32.png) [@TJdude825](https://boards.straightdope.com/u/TJdude825)\
**Post date:** [February 23, 2006, 5:30am UTC](https://boards.straightdope.com/t/clear-boards/345752/2 "2006-02-23T05:30:28Z")

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This was actually discussed recently, in reference to Good Will Hunting, IIRC. You could try doing a search, but I’m pretty sure the consensus was that grease pencil is probably the best for writing on glass. Dry erase also works relatively well on glass.

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**Author:** ![friedo](https://avatars.discourse-cdn.com/v4/letter/f/8edcca/32.png) [@friedo](https://boards.straightdope.com/u/friedo)\
**Post date:** [February 23, 2006, 5:48am UTC](https://boards.straightdope.com/t/clear-boards/345752/3 "2006-02-23T05:48:43Z")

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The only purpose of using a clear board is for the viewer. It allows the actor to write (backwards) without obstructing the camera’s view of the text. Also, it looks cool.

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**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\
**Post date:** [February 23, 2006, 8:49am UTC](https://boards.straightdope.com/t/clear-boards/345752/4 "2006-02-23T08:49:59Z")

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In addition to grease pencils and dry-erase pens, there are pens designed specifically for writing on glass; in my favourite movie, _Amelie_, the (delicious) Audrey Tatou uses one to write a daily menu on a glass partition in the café-tabac where she(or rather, her titular character) works.

In movies, as **friedo** suggests, the main use seems to be that we can see the character face-on, at the same time as seeing what he/she is writing.