Complex balloon decors are usually made with balloons that are inflated with air rather than helium. Helium, although buoyant, escapes from balloons quickly and so would lead to a deflated design within a day. Because the balloons are inflated with air, they must be attached to an underlying structure, made of rods, which will hold them up. Balloons are generally attached to the structure with fishing line or ribbon, although some manufactured balloon rods have clips integrated into their surface.
Aluminum Rod
Pieces of aluminum rod, either rounded or rectangular, are used for creating shapes that need tight curves. The metal frame can be bent to the correct shape and will hold that shape indefinitely. Aluminum also has the advantage of being strong and light, although it can be somewhat expensive. An aluminum rod is usually drilled with a drill press to make holes for the balloons to be attached. If you will be cutting and drilling your own aluminum rod for a balloon structure, remember to sand any sharp edges that could puncture the balloons.
PVC Pipes
PVC is an inexpensive option for building balloon decor structures that only need to use straight lines, corners and very gradual curves. You can use the pre-formed joints available at hardware stores to create complex shapes like star arches or castle outlines, or to attach the structure to a weighted base for support. PVC can be drilled to create spaces to attach balloons, or the surface of the PVC can be scored with a utility knife to ensure that the ribbon or fishing line that is used to attach the balloons does not shift.
Balloon Decorating Strip
A balloon decorating strip is a manufactured plastic rod made of polyethylene and sold through specialty retailers who focus on balloon decorating and party decor. It has molded or drilled holes, or sometimes clips, which are usually spaced one inch apart. This product is most commonly used to create balloon arches or balloon columns, as it is quite flexible.
Hula Hoops
When you see a balloon decor item that is in the shape of a circle, it has most likely been made with a hula hoop as the underlying structure. Hula hoops are generally inexpensive and easy to find. They also can be drilled or scored with a utility knife to prepare the surface of the structure for balloons to be attached.
Metal Pipes
Metal plumbing pipe or electrical conduit is used in balloon structures that need a great deal of rigidity and weight. This is especially common when creating the base of a large arch or for a large structure that will be kept outdoors. Metal pipe does provide a great deal of stability, but cutting it to size and attaching balloons to it can be more difficult than with other materials, so its use is usually kept to a minimum when possible.