This “clam shell” balloon forming machine provides very accurate and repeatable controls needed to produce high-quality balloons. The machine features electrically heated, longitudinally split molds with chilled water cooling. The tubing neck-down is performed in the same machine cycle as balloon formation, making it especially suitable for forming balloons from highly elastic and soft materials. The split mold design allows direct access to the mold cavity making balloon removal simple. Clam Shell molds can be treated with anti-stick coatings (Teflon) to handle a variety of materials, such as soft polyurethanes, that would otherwise stick to the mold surface.