Re: Edible candle, September 2017
I have performed the edible candle demonstration for many years. (It was originally shown to me by Lee Marek.) I usually do it at the end of the first or second class, after discussing observations and doing several experiments where a similar size wax candle has been used for heating. I also use it in my chemical magic shows.
As a safety precaution, the "candle" is kept away from all laboratory chemicals and products of any demonstrations performed in that session.
I cut a piece of potato using a cork borer, about 2 cm (¾ inch) in diameter. I soak the potato in lemon juice for a minute to prevent discoloration due to air oxidation. The “wick” is made from a sliver of a Brazil nut or a pecan. I use a match flame to darken the “wick” so it looks used. Both nuts contain sufficient oil for the “candle” to burn for up to 2 minutes. When the flame starts to shrink, I blow out the candle and continue with additional observations. No one is permitted to handle the candle.
The audience is located about one meter from the candle. I have had a number of students, and even a professional colleague from the Biology department, report that they observed wax melting and dripping down the side of the candle.
At the end of the demonstration, I explain that everything is not what it appears to be and eat the candle just as the class ends. I do not mention this demonstration again during the semester. See my procedure at my website under “Observation of a Burning Candle”.
David A. Katz, Chemist and Educator Tucson, Arizona, www.chymist.com
Re: Lab safety & common sense — not mutually exclusive, October 2017
Very interesting article by Michael Jansen. I agree to most of his points, and completely relate to his call for being brief and practical. However, I imagine that for new or less experienced teachers, it may still be a useful “sanity check” to have the option to read over redundant safety details. Just a thought.