A 20 fluid ounces (590 ml) bottle works best, but you can use a slightly larger plastic bottle as well.
You may need to use a drill bit to puncture your hole if the bottle cap is too thick for a utility knife. In this case, use clamps to secure the bottle cap in place. If you don’t feel comfortable using a drill, ask an experienced adult for help. [2] X Research source You’ll be inserting a straw through this opening, so don’t make the hole too big!
You can use electrical tape or duct tape if you don’t have any hot glue. Just don’t wrap it so tightly that you constrict the movement of air in the straw. [6] X Research source
Blow into the open end of your straw to test it. If the balloons expand, you’re ready to continue. If you hear air coming out, identify the leak and cover it with hot glue. You can also use rubber bands or tape to keep your balloons attached to the straw, but the seal may end up being too tight.
You’ll have a long length of straw sticking out through the top of your bottle cap. You only need 2–3 inches (5. 1–7. 6 cm) of straw sticking out to make your lung work, so feel free to trim the rest of it off with your scissors.
