What is Cargo sweat?

Some cargoes such as hides, skins, ores, etc., exude ( give off) large quantities of water vapour making the relative humidity of the air inside the hold very high. The slightest cooling would cause sweat to form on the steel parts of the hold. This would drip on them. This can only be prevented by use of large capacity exhaust fans ( fitted on most cargo ships) , using dunnage to keep the cargo int the steel and covering the top of the cargo in the hold with bamboo mats or cardboard sheets.