Why does chocolate sweat after leaving the box?

When cold chocolate sits below the dew point of the surrounding air, moisture condenses on it. Because water dissolves sugar, the result is more than wetness: white sugar bloom.

18 May 2026Updated 28 September 2026

Short answer

If the chocolate surface is colder than the dew point of the surrounding air, moisture from the air condenses on it. At 30 °C and 60 percent relative humidity the dew point is about 21 °C, so even product at 18 °C sweats. Keeping the box closed until the product has warmed up prevents it.

When cold chocolate comes out into warm, humid air its surface stays below the dew point and moisture from the air turns into droplets. At 30 °C and 60 percent relative humidity the dew point is about 21 °C, so product at 18 °C sweats too.

The sweat is more than a look: water dissolves sugar, and when it dries the sugar recrystallises on the surface as a white layer called sugar bloom.

Keep the box closed until the product has warmed up and do not leave it open in a humid doorway. Droplets on the outside of the pack point to condensation; droplets inside the box, under ice or a plate, point to a leak.