Leave a bag of gummy bears open for a week and they turn into something closer to jerky. Leave a jar of boiled sweets open in the same room and they can turn soft and sticky instead. Same room, same air, opposite result — because the two sweets are built from almost opposite structures.
Gummies: a gel losing water
Gummy and jelly sweets are a flexible gel, typically gelatine (or a starch/pectin blend in vegetarian versions) holding a significant amount of water along with sugar and glucose syrup. That water is what keeps the texture soft and bouncy. Exposed to normal room air, the water content doesn't stay put — it slowly evaporates out of the sweet, and as it goes, the gel structure contracts and firms up. The sweet isn't spoiling in a food-safety sense; it's just drying into a denser, chewier version of the same gel.
Boiled sweets: a sugar glass absorbing water
Boiled sweets (and hard toffees) are made the opposite way: sugar is heated and cooled rapidly into a near-water-free amorphous solid, sometimes called a sugar glass, which is what gives them their hard, glassy snap. But concentrated sugar is hygroscopic — it pulls moisture out of the surrounding air rather than holding onto water itself. In a humid kitchen or a loosely closed bag, boiled sweets absorb that ambient moisture, and the surface sugar starts to dissolve slightly, leaving a sticky, sometimes cloudy film.
Same fix, opposite direction
Because the two problems are really the same mechanism in reverse — moisture moving between the sweet and the air until they reach equilibrium — the fix is the same action either way: minimise that exchange. An airtight tub or a properly resealed bag, kept somewhere cool and out of direct sun, slows both gummies drying out and boiled sweets turning sticky, simply by limiting how much air (and the moisture in it) the sweets are exposed to.
Frequently asked questions
Why do gummies go hard over time?
They lose moisture to the air, and as the water content drops, the gelatine or starch gel structure tightens and stiffens.
Why do boiled sweets go sticky instead?
Boiled sweets are concentrated sugar with almost no water, and sugar actively draws moisture in from humid air, softening and dissolving the surface slightly.
Does an airtight container actually help?
Yes — for both. Limiting moisture exchange with the air slows gummies drying out and slows boiled sweets absorbing damp, in either direction.