Disappearing Ink and a Fire Extinguisher

Disappearing Ink is a great tool for chemistry teachers to demonstrate acid-base indicators. Just squirt a little on your shirt and the carbon dioxide in the air turns it from blue to colorless. If your breath works well, it only makes sense that a shot of carbon dioxide from a fire extinguisher works great… and it does. Here’s the Fire Extinguisher Demo in action – the lab coat guy looks surprised…

But here’s what you didn’t see on television. I was on set and ready to go with Nick O’Kelly when I looked down at the fire extinguisher and thought to fire off a test blast. I pulled the trigger and… nothing. Nothing! We were less than 30 seconds to air time when I ran to the back area of the studio and pulled the CO2 extinguisher off the wall… broke the tab and I was ready to go. Literally seconds later, the red light came on. I squirted disappearing ink on Nick’s coat just as planned and told him that the secret to making the “ink” disappear was carbon dioxide. When it came time to blast Nick with a little carbon dioxide, little did I know that it would come flying out with the force of a hurricane! The fire extinguisher that I normally use is a kinder, more gentle spray as opposed to a blast.