Budding chemists aren't the only ones who will get a kick out of this enjoyable experiment that teaches something about how the natural world works. When baking soda and vinegar come into contact, they form carbon dioxide. This gas fills the bottle and can't escape, so it rushes into the balloon, causing it to inflate.
Not all pumpkins are orange, nor are they necessarily destined to become leering jack-o'-lanterns. The designs used on these pumpkins, carved freehand, mimic the lacelike openwork of 18th-century pierced creamware dishes, and turn any pumpkin (especially a pale Lumina) into an intricately patterned lamp.