How to fill foil balloons: helium or air

Helium or air: which do you need?

Use helium when the balloon should float: tied to a weight on a table, held by a child, or rising above a display. Use air when the balloon will be fixed to a wall, mounted on a stick, laid on a table or used as a photo booth prop.

Air is free, easy to get and lasts longer in the balloon, so it is the practical choice for shop displays and backdrops that stay up for days or weeks.

Find the valve

Most foil balloons have a self-sealing valve: a thin plastic sleeve at the neck of the balloon, often at the bottom of the shape. Two flat inner layers close by themselves once you take the filler out, so the balloon does not need to be tied.

Before filling, gently smooth the sleeve so it is open and not twisted. A twisted or creased valve is the most common reason a balloon will not take air.

Filling with helium

• Use a helium tank with a foil balloon nozzle, or the foil attachment on a balloon inflator.
• Slide the valve sleeve over the nozzle, past the end of the inner flaps, and hold it in place with your fingers.
• Fill in short bursts. Stop when the balloon looks smooth but the seams still have a slight give.
• Pull the balloon off the nozzle. The valve closes by itself; press the sleeve flat to make sure.
• Tie the ribbon around the neck below the valve, not through it, and attach a weight.

Filling with air

For small and medium balloons, a hand pump with a thin nozzle or a plain drinking straw works well. Insert it past the inner flaps and fill until the shape is smooth. For larger shapes, a hand or electric pump saves time.

Air-filled foil balloons do not float. Mount them on a balloon cup and stick, tape them to a wall or backdrop, or hang them with thread.

How full is full?

Foil film does not stretch, so over-filling splits the seams. Fill until the wrinkles disappear and the shape looks crisp, then stop. Small creases near the seams are normal.

Temperature matters too. A balloon filled indoors and taken into hot sun expands and can burst; one taken into a cold room shrinks and looks soft, then recovers as it warms. Leave a little room if the balloon will move between temperatures.

Common mistakes

• Filling until the balloon is drum-tight, which splits the seams.
• Not pushing the nozzle past the inner flaps, so the gas goes nowhere.
• Leaving filled balloons in a parked car or direct sunlight.
• Tying ribbon through the valve, which can stop it sealing.
• Breathing in helium. It is not safe, especially for children.
• Releasing foil balloons outdoors. The metallic film conducts electricity and can cause problems near power lines.