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.
I suspect the materials are not treated against mold, in the first place. We suggested taking some samples randomly in the factory before production, and testing them in a laboratory. But that kind of test takes 3 weeks (which is sometimes longer than production)!
Another way of avoiding this problem is to absorb the humidity inside the container, by placing desiccants–some in each export carton, and some others outside the cartons.
The key is to place enough desiccants (at least 4 kg per 20′ container for those outside the cartons, from what I heard), but also to select desiccants that work for long enough. Once they are full of water and can’t absorb anything anymore, they start releasing water back into the air!
In my search, I came across a very interesting page on the website of Superdry, a supplier of container desiccant.
Under conditions of 90% humidity and 30 degrees, 1 cubic meter of air contains nearly 30g of water. And humidity can get worse during the freight too, because of condensation:
Fundamentally there are two different kinds of condensation :
Cargo sweat: This occurs when moving cargo from a cold or temperate climate to a tropical one. The air containing moisture or water vapour condenses-out on the cargo or its packing.
Container sweat: This is water vapour in the air condensing or forming on the inside surfaces of the container when moving from tropical or temperate climates to cooler areas.
Fungi, moulds and mildew do not usually cause any problems below approximately 55% Relative Humidity.
The effect or onset of corrosion is a function of many variables where humidity and time are also present.
Has anybody got problems because of humidity inside containers?
We handle a number of steel parts, so mold isn’t an issue but corrosion is. Our specific situation has been that in some cases, parts were moist when packed at the factory.
We have had repeated problems with product shipped from Zhejiang and Jiangsu provinces in the March – June period each year. As most of of products are bagged in heat sealed poly bags, it was clear to us that the problem was moisture during processing at the factory, carried along in the bags. (This could include even near microscopic surface moisture on steel parts plated with clear zinc.) Tests revealed that it took several days after bagging for the corrosion to appear, but appear it did.
We have used VCI (a branded product, stands for Volatile Corrosion Inhibitor) as one solution. A small piece of this paper inside the poly bag provides a corrosion free product. Cost of this material is quite low compared to the cost of sorting or customer complaints. The dessicant packets referred to in the primary post are also good solutions for shoes or other non-metallic products. But as a first step make sure that the products are as dry as possible before packaging!
Brad,
If you place the parts in sealed polybags that don’t let air come in, that’s clearly an issue at the factory level… And quite difficult to solve!
I had never heard of VCI. Thanks for the tip!
Hi, Sure, mold. Even skin,walls, lungs get it in Guangdong. Add vinegar. Wash stuff with vinegar. Moldy smelling furniture breaks the retail salel. Vinegar means one can sell the stuff.
I ask them to spray stuff with one of the silicone treatments. That adds a barrier and makes things much easier to clean. But weeks in a hot high humidity container are lovely for mold.
Vic,
Yes, some provinces of China really get very, very humid. I have heard several times about wall/ceilings starting to show mold, in South China around March.
Hi Renaud,
We import many solid wood items from China, but in this peried of year, we always meet the problem of mold, this occurs on PU leather as well because of the high humidity.
Of course, we have QC team to inspect cargo before shipping, could you kindly suggest me what the minimal percentage of the humidity is, that will cause the cargo mildew? 16% or even less?
Regards,
Quentin
Hi Quentin,
I am sure your QC team has devices to check the wood humidity in the factory. The best is between 8% and 12% (and up to 16% if it’s raining on that day).
For PU leather, it is a different device (it cannot be inserted inside the PU, but it works by simple contact/rubbing). Has your team got one? The acceptable percentage is different, but I’d have to check it up.
Hi Renaud,
Thanks for yor promt reply.
Yes, our QC tested humidity percentage when conduct PSI. Usually, we will accept the cargo if their humidity is no high than 16% and ask factory to place some dessicant inside container, but sometimes, we will have our goods mildew when they arrive, sometimes, it is good. I really don’t know how to make the judgement when we meet the humidity problem.
Quentin
Quentin,
I don’t have any answer for you, unfortunately. Place more desiccants, leave less emptiness (air) in the containers, pack the goods so that they are not in contact with the air in the container…
Hi
For cargo that is very price sensitive & experiences cargo sweating I have a very practical & inexpensive solution. For more information e-mail me on alistair@intekom.co.za
Yup. Same here. I import genuine leather sofa and when it is raining season or very humid in china/foshan, i will get up to 20% lost of material (rotten leather) Even with silica bags and antifungal stickers. I am looking now for humidity controlled containers and climate controlled. The investment in such containers will pay off in couple of shipment.