Low cost Halloween pop-up character

Step 5 Install the air seal

My 1st prototype worked without this step but I had to run with about 50 psi of air, and a lot of it. After making this seal on the top end of the 1/2" PVC I could operate my pop-up with much less air, at 30 psi. Cut 2 pieces of 22mm x 5 M Heat Shrink Tubing. One should be 1/4" long. The 2nd should be 3/4" long. Heat shrink the shorter pieces first about 1/2" down from one end of the 1/2" PVC. Now put the longer one over this and center it over the smaller piece before heat-shrinking. The result should have a flat bulge in the middle. Now lubricate the end with the heat shrink. Since this is a relatively slow moving item (at least when comparing to the speed of sound), I would recommend just using candle wax. No need to heat it, just rub it on the heat shrink. This worked on mine with no problems.