How firm should I inflate the balloon?

Modeling balloons should be inflated using a pump and essentially leaving the tip uninflated, so that the air in the balloon would have place to expand while bending the shape. Every shape requires a modeling balloon of a particular length.

Figure balloons are recommended to be inflated for two times: after inflating for the thirst time, you need to release the air, and after second time you can already tie up the balloon. Inflated in such manner the balloon will be more elastic and firm.