The Science of 10%–12% MC: Eliminating Transit Mold in Ocean Containers

Why do containers cause mold?

When shipping natural fiber goods through the equatorial heat of the Indian Ocean or Red Sea, shipping containers regularly experience "container rain", a cycle where 90%+ humidity evaporates during the day and condenses onto container ceilings at night.

If natural rattan is packed at 18% to 22% internal moisture content (the typical level of sun-dried fiber in rural workshops), fungal spores awaken within 96 hours, leading to widespread surface mold.

How we dry rattan to 10%–12% moisture content

At PT Exterio Indonesia, we eliminate this hazard through our closed-loop 72-hour convection heat chambers (oven pengeringan). By circulating continuous 55°C–65°C hot air, we draw deep capillary water out of the rattan core until calibrated digital pin-meters register strictly between 10% and 12% moisture content.

Desiccants and container preparation

Combined with heavy continuous 2kg calcium chloride desiccants hung every 2 meters inside the container, our goods arrive crisp, dry, and ready for immediate retail floor placement anywhere in North America, Europe, Australia, or the Gulf.

What 10%–12% moisture content means in practice

Moisture content is the weight of water in the fiber as a percentage of its dry weight. At 10%–12%, rattan sits in balance with typical indoor air in most destination markets. At 18% to 22%, it holds enough water to feed mold if conditions in the container allow it. The gap between those numbers is the whole reason a drying stage exists.

Why drying alone is not enough

Dry goods can still pick up moisture in a poorly prepared container. That is why drying, packing and container preparation are treated as one process: dried product, clean cartons, desiccants placed along the container, and a sealed load. Skipping any one raises risk, which is why we do not rely on desiccants to rescue goods that were never dried properly.

What mold on arrival costs a retailer

Surface mold on a pallet is rarely a small problem. It can mean cleaning labour, delayed shelf dates, rejected cartons and hard conversations with customers. Buyers who have been through it tend to ask about moisture before they ask about price, and we think that is the right order.

Questions buyers ask about drying

Does kiln drying damage rattan? Not when the temperature and time are controlled. Our cycle runs at 55°C–65°C over 72 hours, which dries the core gradually rather than shocking it, and pieces are checked with pin-meters before they are packed.

Is sun drying enough? Sun drying alone depends on the weather and usually leaves moisture higher than the range needed for sea freight. That is why we treat the convection chamber as a required stage, not an option.

How buyers can verify moisture control

• Ask the supplier for the target moisture range and the instrument used to measure it.
• Ask whether readings are taken per batch before packing, not once a month.
• Ask what desiccant and container preparation is used for sea freight.
• Spot-check arriving goods with your own pin-meter.

Moisture control sits alongside legality and quality documents. See SVLK certified rattan explained and our Buyer FAQ for the full set of export standards.