Looking for decor that really *pops*? Or something that can add that *burst* of color? A Bubble Window allows the string-puller to create a infinite number of wobbling, ever-changing window paintings. All with a just a wee bit of bubble solution and physics. I made this one for my classroom, but you should make them for any purpose and size you wish!

What: Bubble Window!
Concepts: interference, light, refraction, waves, physics, art
Time: ~ 1 hour
Cost: ~ $10
Materials:
- 3/4" PVC (about 6')
- 6 x elbow joints (3/4")
- 6 x T joints
- 2 x PVC end caps (3/4")
- 1/6" steel cable (about 5')
- 4 x 1/16" ferrules (cable holders)
- 4 x eye hooks
- 2 x small L brackets
- nylon string (about 4')
- pulley
- tub
- bubble solution (I used store-bought, but there are many recipes online like this whole wiki)
Tools:
- PVC cutter
- Cable cutter + crimper
- Glue

Let's bubble!

Step 1: Assemble PVC Frame

Measure and cut your PVC frame. This can be however big you want it to be. I made this one so it would be about as wide as the tub I had around, but yours can be anything! I included by measurements here, which ended up being about 2' tall with legs at the bottom.

Step 2: Prep Your Crossbeam

On the top crossbeam, you're going to add two eye hooks (for supporting the bubble bar), and a pulley in the middle to put a string through to raise it up. I measured an inch in from each side for two of the eye hooks, and put the pulley on an eye hook in the middle.

For each eye hook, use a small drill bit to start a hole in the PVC and use your hands to twist it in all the way. You can open up an eye hook with a pair of pliers to get the pulley on, and then bend it back to closed.

Step 3: Prep Your Bubble Bar

Cut a length of PVC that's shorter than your tub is wide. Measure the distance between the two side eye hooks on your crossbeam, and drill holes for the cable to pass through on the bubble bar. In the middle, drill a hole and add an eye hook to tie a string to for lifting.

Step 4: Add Tub Hardware

We're going to need a way to fasten wire to the tub. I used small L-brackets, scoring both the tub and the bracket before gluing them down. I initially tried Weld-It for the glue, but found that copious amounts of hot glue worked just fine. It always does!

Step 5: Rig Your Wires

"Ferrules" are the name of these little wire holders. Add a ferrule on one side of the wire, and loop it through the L-bracket on the tub. When you have it in place, crimp it together so it won't go anywhere. Then wire your bubble bar through, making sure the eye hook on the bar is pointing up. Then attach the wire to the top eye hook, making sure the wire is relatively taught.

A few tips: unlike me, if you keep the end of the wire in the ferrule when you crimp, it will hide the pokey end of the wire. This will be easier on people's hands. It's also hard to get the tautness just right. Take your time. If you need to shorten your structure, that's okay. If you need to undo a ferrule, you can by applying pressure with pliers on the side.

Almost there!

Step 6: Attach Your String

I used nylon string, but you can use whatever you have around. Tie it to the eye hook on your bubble bar, and feed it through the pulley on the crossbeam. If you want, you can add some weight at the end, or tie some knots as a small handle for later.

Step 7: BUBBLE BUBBLE BUBBLE TIME!

Pour in some of your bubble solution, and it's time to bubble! Pull the bubble bar up, and watch the panel you've made. You can blow bubbles with short breaths of air, make it wobble with soft breaths, and watch the amazing magic of bubbles. You may find after the first few times

Some things to do and notice include:

Notice the colors in your bubble window. What happens to them over time?
Try shining a bright light (or the sun) on the window on the same side you are on. If you look at it in the reflection, what happens?
You can make the bubble window wobble in bigger and bigger ways if you blow in time with it like you would while pumping your legs on a swing. See how large it can go before it pops!
With the light on one side, place some white paper on the other, and look at the shadows cast by the window. What do they look like?

Oh, you'll just be bursting with joy!

Step 8: Bubble Colors and Physics

The colors on a bubble are amazing. They may appear at first to move randomly, but they actually have a very specific significance. This mostly has to do with the process of interference, which has to do with when two waves are in the same place or "superpose" each other. This happens at the beach when you watch a wave leaving intersect with a wave coming in. Or when you and a friend wobble two ends of a jump rope. It also happens with light.

When light enters your soap film, some of it gets reflected right away, and some passes through, and reflects only after its hit the back edge (see the drawing). The wave that reflected on the back edge has gone a bit farther and changed direction a little bit, and so may be out of sync with the other light wave. Depending on how they line up, they can either add to the magnitude of each other's waves (constructive interference), or neutralize each other (destructive interference).

What's fascinating about bubbles is you can tell how thick the soap layer is by what color you can see! It's amazing! The light coming in probably starts at white light (if it's the sun or many standard bulbs). As light bounces inside, only the light that escapes will we see, and different colors respond to different thicknesses. You can find an incredible write-up by the Exploratorium on this here.

When the layer is thick, you will see blue-green, down to blue (a little thinner), then magenta, then yellow, and finally black (the thinnest), and this means that the bubble wall is about to burst! You can see this in the second photo as black starts to form with occasional rivulets of bubble solution thickening it up as it comes down from the top bar. If you leave your wall very still, you may even notice that it starts to settle in horizontal lines!

Have fun, and as always, keep exploring. I'm excited to hear what you come up with in the comments below!