You can add more helium to a deflated foil balloon (assuming the balloon is not damaged), but you need to make sure you tie your ribbon below the self-sealing valve when you initially inflate the balloon. Otherwise, it will be very difficult to get back into the seal to inflate the balloon. Simply inflate the balloon as you did before. 

A few things to note:

  • Helium sold in cylinders is never 100 percent helium. Some disposable tanks have as much as 20 percent air inside them. Helium supplied by gas suppliers should be closer to 100 percent helium. Air traps in the balloon, so the more air in the balloon the less likely the balloon will float. The more times you fill the balloon, the more air there will be trapped inside. Air does not float.
  • The more times you fill a balloon, the more likely you will damage the self-sealing valve.
  • Manufacturers do not guarantee balloons are refillable.
  • A balloon should appear close to fully inflated for at least 7 days. If a balloon deflates quickly after inflation, the balloon may have a hole in it or damage to the self-sealing valve. You can try flattening the valve, but we recommend not wasting helium on a damaged balloon.