Several clients asked me recently about a way to avoid mold on imported products shipped from a Chinese, Vietnamese, or Indian factory. This is a serious problem.

The reason is usually a combination of these 5 factors:

1. The products are contaminated while in the factory, and/or
2. The products are too wet when packed, and/or
3. They are packed with wet packing materials, and/or
4. There is a lot of air in the packaging and that air is very wet, and/or
5. The air in the container is or gets wet. Then, during long transportation, mold develops.

So, what are the best ways for avoiding mold on imported products shipped in an ocean container..?

Avoiding or reducing mold on products shipped by container

Here are effective ways to mitigate this risk:

• Mold comes from contamination with mold spores somewhere in the factory (or a sub-supplier’s factory/warehouse). Have a specialized cleaning company come and do a deep cleaning!
• If contamination is an issue, a ‘lighter’ solution might be dipping each piece in white vinegar (it is food grade). Other substances can be considered, too. But who knows if it will go deep enough into the fibers?
• The products are too wet when packed: Some buyers require the factory to ‘bake’ the products, or at least parts of the products, in an oven just before packing. It will dry them up. I suggest you discuss this with the supplier. Another approach I heard of is applying an antimicrobial coating on the products. Some coatings don’t contain harsh chemicals but act as “swords” that puncture organisms — someone from Cams Sanitize tells me their CS90X coating operates this way.
• They are packed with wet packing materials: If the cardboard materials are of low quality and they are stored for months, they will suck up a lot of humidity. That can be avoided by procuring cardboard packing materials just 1 week before shipment, by avoiding low-grade cardboard and by avoiding wooden pallets.
• There is a lot of air in the packaging and that air is very wet: This would require some redesign of the packing, to include less air. Some desiccant could also be placed inside the packing, but that’s not a perfect solution, as it will absorb humidity and then release it back into the air.
• The air in the container is or gets wet: You can require an air-tight container (and it can be inspected relatively easily – when we do that, we close the doors and we look for any light coming from holes) and request the supplier to place desiccant material in the container.

If you have never heard of desiccants, I suggest you read this article: Avoiding humidity inside containers“. It started with a client’s problem:

Last week, an importer was asking us how to avoid the formation of mold on the shoes they ship from China to Chile. The goods stay up to 50 days inside the container, so that was an extreme case.

A packaging expert’s insight

This morning I received some insightful comments from a packaging expert, Kevin Howard. I already published some of his advice in the past (for example, about packaging optimization) and I am always blown away by the depth of his experience.

Here are his tips for this situation:

Humidity in ocean containers from Asia has been a problem ever since there have been ocean containers, but there are some really effective ways to minimize and/or eliminate such issues, sometimes without the use of desiccants.

Desiccants and effective use of them

First, though, you should know a little more about how desiccants work. Did you notice on the Superdry site that their test data for effectiveness was based on a sealed chamber? A sealed chamber controls the exact amount of humidity/moisture available to the desiccant, while an ocean container is not airtight. As a result, it would be difficult/impossible for desiccant to really absorb all the moisture available in an ocean container.

Also, when thinking of the volumetric space of an ocean container, one should remember that it’s possible to displace much of that volume by densely packing the container with products. Unfortunately, shoes are not very dense, nor is the package surrounding shoes. This type of product and packaging make for a worse case condition, but there are ways to mitigate the situation.

The most effective use of small packs of desiccants can be found on items like cameras that have tight-fitting packaging surrounding them. Some cameras use molded expanded polystyrene foam (EPS) that fully encapsulates the camera. By creating this kind of foam box, only a small amount of desiccant is needed to absorb moisture found in the cavity of that foam. If the shoe manufacturer needs to use desiccants, it would be wise for them to use plastic bags to tightly surround a few boxes at a time, thus limiting the amount of free air space that the desiccant must act upon. If they could pull a vacuum on the bag, they’d have even less moisture left in the void spaces.

Reducing moisture through the use of optimal packaging materials and methods

Many companies don’t realize they are introducing moisture into the system by the types of materials they use. Many Chinese boxes are soft and not very dense and have higher moisture content than materials found in the US. If the shoe manufacturer is using the cheapest possible box material, which not only starts with high moisture content but also absorbs moisture like a sponge as it travels through the distribution system, then they are placing moisture-sensitive products in a moisture-absorbing/producing material. The same goes for pallets. I have seen a number of times where pallets from Asia produced a tremendous amount of humidity in ocean containers. Replacing wood pallets with plastic slip sheets eliminated the problem, plus allowed more products per container.

The shoe manufacturer may want to consider not using boxes for ocean shipment, along with eliminating pallets (if they were using them). If they shipped each pair of shoes in individually sealed bags with a small amount of desiccant, they’d be able to increase load density by a significant percentage while eliminating the humidity issue. They would need to postpone the packaging operation until the shoes arrive in Chile, but the savings in damages, handling, storage and shipping would pay for having a packaging line in Chile. Postponing the packaging would also allow this company to provide different SKU’s to different customers, all based on different packages for those specific customers. With the costs of ocean containers continuing to climb, it’s more important than ever for companies to consider ways to densify their products as much as possible, and postponing the packaging is oftentimes a viable way to do just this.

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Have you had any bad experiences with mold forming on your imported products which had been shipped by ocean container? How did you overcome this issue? Let me know your thoughts and questions by leaving a comment.

*Editor’s note: This post was originally published in 2011, and has since been updated to include new information and formatting in February 2019.

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