10.3.3   Water vapor in the container
Water vapor conditions in the container are primarily determined by internal factors, i.e. the water vapor conditions are largely determined by the hygroscopic properties of the cargo inside. The quantity of water vapor contained in the air is small and does not generally result in sweat damage. However, it may lead to other damage, e.g corrosion of metal goods.
Relatively large quantities of sweat in closed containers are always attributable to the cargo or its packaging (and/or the container floor if wooden). Sweat is thus actually possible only if water enters the container with the cargo. High air temperatures in the container and the associated low relative humidity drive water vapor out of the hygroscopic cargo. This water vapor condenses on the container walls and ceiling which is cooled by nocturnal radiation. Investigations reveal among other things that, starting with a dry container ceiling and side walls, sweat coverage increases in stages and reaches a maximum after a few days.

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