Prepare the table

Create a paper pattern

…that is 1/3 to 1/2 larger than the intended balloon size. When inflated, the flat dimension of the pattern becomes 1/2 of the circumference of the finished balloon. Draw a filler neck somewhere along the edge of the design that is 1" wide by 4" long. If your design has a thin appendage, you may use that as a filler neck. The balloon is inflated through the filler neck and then sealed. If the filler neck is too short, you must permanently heat seal your balloon.

Secure the foil

…to the work surface by stretching it tight and taping it (Nylon side up) to the paper. Again, there must be no wrinkles. Then tape a second piece of foil on top of the first (Nylon side down). If you use only one piece of foil that is folded in half and taped (Nylon side in) then take extra care that there are no wrinkles underneath.

Place and secure the pattern

…on top of your 2 sheets of tensioned foil. Trace around the pattern with a crayon or permanent marker. Remove the pattern and put it aside, or leave it in place for extra protection.

Plug in the iron

…and set the heat. The test for the proper temperature is a good seal. Test using thin strips of scrap material, heat and press an edge together. Do not work near your pattern to avoid sealing material where it should not be. Wait for the foil to cool then try peeling the seam apart. If the iron is too hot, the seam will melt or become crisp. If the iron is too cool, the foil will peel apart easily. Do not place hot tools on your working surface, always place the hot iron on a non-combustable surface on the floor under the table.

Seal your balloon by pressing the iron around the outside line of your pattern. Begin on one side of the filler neck (do not seal the end of the filler neck). Slide the iron continuously around the design without picking it up or tipping it on its edge or pointed nose. Use a sheet of wax paper between the iron and foil for easier ironing and better looking seams. Remember to place the hot iron on the floor when finished. Leave it plugged in for now.

Plug in the hot knife

…and wait and for it to heat up. Again, test the hot knife on the foil away from your balloon so that it cuts easily by melting.

Cut out your balloon around the outside of the sealed edge with the hot knife. Leave at least 3/8" of sealed edge around the entire balloon for strength. Move the knife slowly, cutting through both layers of foil. Curve any change of direction in order to avoid creating a chop mark which could cause a tear.

Gently remove the balloon

…from the table by peeling it up. This is a delicate operation so go slowly. Then remove the remaining foil from the table. Place the balloon back on the table upside down.

Check the back side seams

…for a good seal. If they are gathered, blistered or otherwise not sealed then re- iron them.

Inflate your balloon

…with air or helium. Be careful! Rapid inflation or overfilling can tear or peal the seams open. Gas inside the balloon will expand with heat, sunlight or increased altitude and can burst the seams so do not overfill.

Heat seal the filler neck

…with your iron leaving most of the filler neck for reuse. Unplug your tools and clean your work area.

Safety first!
Remember that balloon foil can conduct electricity.
Do not allow the balloon to touch electrical wires!