Air forms may be full or partial spheres, ellipsoids, cylinders, and varied mix-or-match combinations of these shapes. Irregular or free-form shapes also can be used.
PVC coated nylon and polyester fabrics are usual choices for air forms. The material must be strong enough to resist inflation pressures typically in the range of 1 to 3 inches of water column pressure, or about 0.04 to 0.11 psi. How the balloon may stretch or deflect under this pressure must be carefully considered.
Flat pieces of the air form are heat-sealed together with a bar sealer or rotary welder so that they stretch into a smoothly curved surface when inflated.
HANDLING AND INFLATING
While the smaller cylindrical forms are easily carried in a pickup truck and handled by two workers, the larger dome forms may weigh as much as 5 tons. Although the material is strong when inflated, it must be carefully handled to prevent punctures. A high-volume, low-pressure blower is used to inflate the form to its design shape at the pressure designated by the form designer.