Bubble Suspension

 My museum owns an exhibit from the Exploratorium called "Bubble Suspension."

You can read all about it here, but the exhibit is basically a chamber filled with relatively dense carbon dioxide gas. Blowing a bubble into the chamber results in the bubble hovering on top of this invisible gas layer for a long time, suspended in mid air. The carbon dioxide is provided by dry ice.

Beautiful! This is one of my personal favorites, really. It's a well-designed exhibit, and I know our visitors like it, too. So it came as a real surprise when I heard that a weekend visitor had fallen into the exhibit and turned blue! An unattended child had used a stool to reach the top of Bubble Suspension, and fell into the chamber. There is no oxygen in there, mind you. The child was fine because he was pulled out quickly, but a lung full of CO2 is enough to make you turn blue. He went to the hospital and checked out just fine, and there were no side effects. Still, it could have been worse. So I was given the task of preventing that from happening while maintaining the exhibit's function.

I ordered a custom acrylic dome to match the diameter of the opening in the top. After about 6 weeks, it arrived. This picture shows it already attached, with a hole in the front for blowing bubbles into the exhibit.

Now we needed to attach it to the top of the exhibit, but make sure it's easy to remove for cleaning. I fabricated three custom pocket lockers and attached aluminum tabs to the dome that could lock it into the top of the exhibit with a twist.

While the exhibit was being refurbished, I decided to replace the well-used plastic bubble wand with something a little more durable. I'm not exactly sure what kind of bubble wand was originally shipped with the exhibit, but the wand attached to the exhibit at that time was a real veteran of many visitor experiences.

 Here's the prototype. Who knew there was so much usable stainless steel in the office kitchen?

The Delrin washers are grooved to provide an abundance of surface area for bubble solution to cling to. I hand made these from a 3/4 inch diameter Delrin rod.

And here's the final update. Bubbles are blown into the chamber through a 6-inch hole cut in the face of the acrylic dome.