You prevent container rain mainly by controlling moisture before the doors close: ship product that is within its moisture specification, in a clean and dry container, never warm or wet, with lining and desiccants on longer routes.
Container rain is condensation that forms on the inside of the roof and walls and drips back onto the cargo. It causes wet patches, caking, mould and sometimes aflatoxin growth. Insurers and suppliers often argue about who caused it, so prevention is far better than a claim.
Why it happens
Dry agri goods still hold some water. In a sealed container, warm days release moisture from the cargo into the air. When the container cools at night, or the ship moves into a colder region, that moisture condenses on the steel roof and walls. The cycle repeats every day of the voyage.
The risk is higher on long routes from India to northern Europe or North America, in winter at destination, and when goods are loaded in the monsoon months.
Steps at the factory
- Test moisture on the loading sample and do not ship if it is above the contract limit.
- Let goods cool to room temperature after drying, cleaning or sterilisation before bagging and loading.
- Store bags off the floor and away from walls in a dry warehouse before loading.
- Do not load in rain, or from an uncovered yard, unless the loading bay is fully protected.
- Use only dry pallets if pallets are used. Wet wood adds a lot of water.
Steps at the container
- Reject a container with a wet floor, holes or rust that lets water in, and ask for another.
- Line the floor and walls with kraft paper, and add a roof lining where drips are likely.
- Hang desiccants along the side walls, as explained in desiccants and container liners.
- Leave a gap between the top layer and the roof.
- Ask the shipping line if ventilated containers are available for your product and route.
Product by product
Dehydrated onion and garlic, spice powders and psyllium husk pick up moisture quickly and cake. Oilseeds such as groundnuts and sesame carry their own risk of mould and aflatoxin, covered in preventing condensation and mould in oilseed containers. Whole seed spices are more forgiving but still spoil if loaded damp.
Moisture limits depend on the product, grade and your market. Agree them in the specification and test against them at loading, not just at sampling months earlier.
How we help
We check moisture on the loading sample, inspect the empty container for leaks and damp, and confirm lining and desiccants are fitted before sealing. If a product is too wet to ship, we tell you before it leaves the factory. Ask for a free sourcing review to plan a moisture-safe shipment.