Friday, October 31, 2014

In defense of the rainbow flame demonstration

VTJ has previously written in the comments in defense of the "rainbow flame" demonstration and has advocated strongly and eloquently against a blanket ban. I've invited VTJ to comment more: 
Use of methanol in school and outreach-related demos has been the subject of a lot of attention and discussion. While some of the articles that I have seen recommend what I would call appropriate precautions (see the CSB guidelines), many people have advocated elimination of these demos from our teaching repertoire. What I find even more troubling are the comments from teachers stating that, because of these incidents, they will never use alcohol flames in their teaching. I worry that that fear might be transferred to the students and will give further fuel to the chemophobia that is already so prevalent in our society.  
I am a synthetically trained graduate student who has been very involved in chemistry outreach programs for several years and who is going into education. I have presented at dozens of schools, doing demos that include clock reactions, the Tollens’ test, liquid N2, and electrochemical plating. I have also done the rainbow-flame demo over a hundred times. While I have seen the variants of this demo that use nichrome wire or wood splints instead of bulk methanolic solutions of the metal salts, I have never found another form of the demo that is as impressive for a classroom/assembly setting. However, if a simpler, potentially safer version of the demo would teach the same concepts, why am I strongly advocating for the methanolic version?
It was the rainbow-flame test that first captured my imagination in a high school science class; not the concepts that Mr. Page was trying to teach but the visual display itself. As a grad student, I have received many thank-you notes with pictures of the flame test drawn on them. Part of the reason I am so attached to this demo is that it seems to captivate the students more than most other demos. We live in a world that is filled with special effects and CGI; the rainbow-flame test, for many young minds, takes Hollywood magic and strips away the curtain. It makes science cool and real at the same time.  
I don’t want every student to walk away saying that they will be a chemist when they grow up. I do want them to leave thinking that science is fun, interesting, and something that they want to know more about. As education becomes more sterilized and legislated, and where more science programs are moving towards “virtual chem” labs for cost and safety reasons, I am cautious about showing another YouTube video in class. When I move away from physical demos and experiments, I worry about two things: that students will go into the real world thinking that chemistry is too dangerous to actually handle or that chemistry is all special effects, with no real-world use or need. 
I agree that safety must come first. I am familiar with Calais Weber’s case and I feel that there is no reason for that sort of accident to happen again to anyone. We need to make sure that we, as educators, do not become complacent about the flammability of methanol, in the same way that complacency with alkyl lithium reagents is unacceptable for academics or industrial chemists. Part of the rainbow-flame demo should include an explanation about why we pour the methanol BEFORE lighting any of the solutions or why we use a small container of methanol and wait for the flame to go out before we refill anything. I always deliberately point out my gloves, lab coat and glasses, as well as reminding students to stay back while I am performing demos. 
I have seen several suggestions that the teachers need more training and I agree that science education majors should probably take a course on lab demos and technique. However, my wife taught high school chemistry for several years and I am familiar with the actual training that most education programs currently provide. A more realistic solution might be a blog, dedicated to curating a list of common demos, along with the practical and theoretical considerations for those demos. If this blog received sufficient circulation (perhaps with the blessing of the ACS, CSB, and/or some teaching organization), it would offer a much-needed update to the Shakhashiri series and could offer graduate-level guidance for educators who want to show their students everything that chemistry has to offer.
CJ thanks VTJ for a thoughtful response on this issue. 


  1. I think VTJ's idea of a blog for demonstrations is excellent. It would be the best way to make information available to the greatest number of people.

  2. Why not burn the methanol in an alcohol lamp? We used to use them in middle school (admittedly, 50 years ago) to heat slides and nichrome wire loops in bacteriology experiments. I don't recall any problems with that approach.

  3. Thanks VTJ for a well-written defense of the methanol experiment. I think your point at the end of the second paragraph about students going into the real world thinking chemistry is too dangerous is a good one. In addition to the wow factor, I think demos like this can teach that chemicals don't need to be feared but treated with respect. That seems particularly salient in an era of food babes, 'chemical-free' products, and widespread chemphobia. It definitely sends the wrong message to avoid doing experiments and demos that can be done safely with appropriate precautions.

  4. I think part of the problem is many of these demos have not been updated for modem technology. We keep using the same stuff from the 50s.

    Why do so many of these demos use a burning beaker of methanol rather than a Bunsen burner (either portable off a small butane tank or hard lined)? A portable Bunsen burner is ~$50 online and a blowtorch with piezo-electric ignition is $19.99 at the hardware store. It seems as though simple updates could make a big difference.

    Also rather than methanol for the metal salts, using ethanol, isopropanol, or diluting with water would all lower the vapor pressure of the flammable gas and help mitigate the risk of some of the demos.


looks like Blogger doesn't work with anonymous comments from Chrome browsers at the moment - works in Microsoft Edge, or from Chrome with a Blogger account - sorry! CJ 3/21/20