How do crayons work?
Dear Straight Dope:
My wife and I were introducing our girls to the wonder of crayons when my wife asked me if our 15 month old twins understood how the wax heat transferred onto the paper. I responded that they probably did not since their father did not know either. My question is, how do crayons work? Is it the slight bit of heat created by friction that melts the wax? Or is it something simpler?
When I think of crayons, I think of Binney & Smith, makers of Crayola crayons. So I checked to see if they had a web page. Sure enough, they did. I sent your question in to them, and got the reply below, complete with 800 number in case I needed more info. The answer is interesting enough, but what impresses me most is the fact that Crayola has TECH SUPPORT!
Anyway, here's what I got back:
Dear Crayola Consumer,
Thank you for your e-mail. In response to your question, "How do crayons work?", it is the nature of the materials at room temperature. The paraffin wax and stearic acid are susceptible to being transferred to a substrate when pressure is applied and the crayon is moved over the substrate. Friction and the heat produced play a small role, but the crayon would probably still lay down material without friction heat because of the physical nature (its relative softness) of the crayon base at room temperature.
If you have any further questions, please call (800) 272-9652 weekdays between 9:00 AM and 4:00 PM Eastern Time and a representative will be happy to assist you.
Thank you for your interest in Binney & Smith and Crayola products.
Stay tuned to our site as exciting updates and new features take place!"
So it looks like crayons lay down color MOSTLY because the crayons are soft, and a bit of friction-induced heat helps it along. There's some project ideas at that website, in case you can't figure out what to do with crayons on your own.