[ELI5] Why do latex balloons deflate in roughly a day but a metallic balloon will last years?

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[ELI5] Why do latex balloons deflate in roughly a day but a metallic balloon will last years?

In: Physics

Latex is porous – it contains tiny little holes. Helium is a tiny molecules, so it slowly passes thorough these pores and out of the balloon, deflating it. Meanwhile a mylar balloon has a denser structure that doesn’t allow helium out.