Alice In WonderBra

The CO₂ Adaptor

The Valve

The Balloon

The Tube Assembly

In this costume, Alice is packing heat.  Or perhaps more correctly, she's packing cold.  Strapped to her thigh is a white nylon webbing holster containing a CO2 cartridge.  This is completely concealed by the petticoat and the dress, so nobody in the audience knows what's coming.

The holster buckles around her thigh at the bottom, and around her waist at the top, with the pocket itself between those two straps.  Inside the pocket itself is a CO2 cartridge adaptor for a paintball gun (paintball guns are officially called "markers," to distinguish them from true projectile weapons), and a braided-steel-reinforced tube comes out of the adaptor.  That tube wraps around Alice's waist, duct-taped to the webbing, where it terminates in a slide valve, hidden under the pinafore.  Out the other end of the valve runs regular fish-tank tubing, which is connected to a balloon, which sits on Alice's chest.  Slide the valve, and the cartridge discharges into the balloon.  Instant breast enhancement.

We knew early on that we wanted to do this with compressed gas, but had some difficulty finding what we needed.  In paintball, normally you have a large, rechargeable canister of compressed CO2 screwed into your gun, which has enough gas to allow you to play for quite a while.  This seemed a reasonable apprach for us to take, but had several problems.  The most obvious one is that even the smallest canisters are bulky, and would have readily shown through Alice's dress.  But equally important was that, with that much gas, Alice would have had to both turn on and off the switch, occupying her hand throughout the presentation.

Thankfully, some paintball guns are made for disposable 12-gram CO2 cartridges, and there exist adaptors to fit 12-gram cartridges into the connectors of regular guns as well.  And while 12-gram cartridges don't give you much in the way of staying power, they do give you just about 5 liters of gas, which was just about right for Alice's miraculous transformation.  We found a plastic paintball gun that took CO2 cartridges at a Wal-Mart on the Cape, and I proceeded to disassemble it to look more closely at the CO2 cartridge mounting.

CO2 adaptors are all pretty much the same - you have a rubber gasket with a sharp metal tube in the middle of it, so when you push your cartridge against it, the gasket seals as the tube punctures.  With our adaptor, you put a cartridge in the plastic bottom part, and screw that into the top.  But this does mean that you nead to put a valve at the end of it, because once you lock and load your cartridge, your system is at full pressure.

CO2 cartridges are filled with liquid CO2, and when you puncture them they evaporate forcefully.  I don't recall what the partial pressure of CO2 is at room temperature, but it's high.  Probably in the 150-300psi range.

Initially, I tried regular fish-tank tubing straight out of the CO2 adaptor from the plastic marker, just to test its strength.  Don't do this.  It failed almost immediately, and nearly blew our ears out.  Then we went to the hardware store looking for stronger hose, but the best they had was 45psi hose - still nowhere near strong enough.  And we still had to find a valve that could withstand that pressure, and fittings.

Eventually, we found a paintball supply store (Boston Paintball in Framingham) that had everything we needed.  Since paintball equipment regularly operates at very high pressure, the reinforced tubing, CO2 adaptor, and even the small slide-valve were perfect.  Actually, they didn't quite seal properly at the junctures (the components all had threaded ends), but a little silicone fish-tank sealant cured that problem fast.

So from the CO2 cartridge to the valve worked at high pressure, and from the valve to the balloon only had to allow CO2 to pass.  We taped our trusty fish-tank line to the end of the valve, and ran it into a balloon.  The end of the fish tank line was quite sharp, though, and kept cutting our balloons.  Rather than melt the end, which would still have left us with a hard tube, we duct-taped a small cube of foam rubber to the end, making it quite soft.  Finally, we tied some string to the ends of the balloon to help secure it to Alice's brassiere.

The balloon was a long, cylindrical balloon.  I think the packaging said 3 or 4 feet long.  However, it didn't fill evenly.  It expanded to full width in the very middle when you began inflating it, and that full-size area grew as more air was put in.  This was great luck for us, since we didn't have to constrain the balloon or try to shape it.  It just naturally inflated like we wanted.  We tied the string to the uninflated ends, and duct-taped the very bottom of the balloon to the fish-tank line.

The valve was a little difficult to slide when we first got it, but some sewing machine oil quickly fixed that.  We also attached a 1/2" hose clamp to it for a better grip.  For the presentation, we first wiggled the valve to loosen it, locked it in the closed position, and then loaded the CO2 cartridge.  The pressurized area got immediately cold, and there was a short hiss as it all came up to pressure. 

During the presentation, Alice puts the piece of the mushroom in the pocket of her pinafore right below where the valve is under her dress, and feels for the valve as she takes her hand out of her pocket.  With her other hand on her hip holding the braided tube, she is able to easily slide the valve to the open position.  The CO2 cartridge is discharged through the tubes into the balloon, and everything gets very cold very quickly.  She was glad that there was not only the webbing holster, but bloomers and tights between the metal parts and Alice's skin.  We'll sacrifice a lot for our art, but frost-bite in May isn't something we'll take.

Continue on to the caterpillar.