MC for international shipping
Concerns of moisture content in jobs destined for overseas. November 18, 2002
I'm making some furniture for a client in Taiwan (to replace another reputable company's pieces that the veneer bubbled on). I hear it is very humid there and I'm sure that whatever I build, no matter how well done, will also grow and bubble. Are there charts for the MCs of the world? I could humidify the furniture before assembling and finish, wrap in plastic and ship. Any thoughts?
Furniture built with expansion in mind with a good water resistant finish should be able to go anywhere. Big words for someone whose name won't be on it, but I believe it to be true. I work mostly in solid wood, though, and don't know much about veneer. If it's bubbling, it could be the glue to blame.
From the original questioner:
Built for expansion is one thing, but a whole system of joinery that is 9% and becomes 15% will still create finish and joint out-of-flush problems eventually, no matter if it has eight layers of polyester on it. It will eventually grow, even if it takes five years. We'll be doing both solid and veneer. Our finishes are top notch for water resistance, but I think we will need to up the MC of the wood to match the humidity of Taiwan, then assemble.
6-7% MC change can be had here in the USA if a piece was moved from one part to another. Will this furniture be in an area with no climate control? I'm thinking that a piece of furniture with finish, once EMC is reached, would not fluctuate quite that much from seasonal breathing. I don't have a clue about climate conditions in Taiwan, but I spent time in Korea, and conditions there are similar to New Jersey area.
Get your client to send you local wood. Build it and get it out of there as soon as possible. Just do the piece before the wood's jetlag wears off.
Because it is an island country, the EMC (which is the MC of the air related to the MC that wood will eventually achieve) is much higher than in the U.S. As mentioned, no matter what the finish, the MC will eventually achieve the average EMC of the air. EMCs in interior locations will run over 10% EMC - often 12% EMC - in this country. If you make furniture, cabinets, etc. in the USA and ship them to Japan, Taiwan, etc., they will swell considerably and develop associated defects. Making furniture at 12% MC here is not possible as the EMC in storage, the plant, and in shipment will be much lower.
From the original questioner:
Is it possible to simply shrink wrap after using wood that is 12%? Or won't a good poly keep the moisture in for the two to three weeks it takes to ship? It's a lot of work and money, so it would be nice to figure it out.
Poly is great if used to provide 100% coverage and sealed tight.
I live in Indonesia and I think Taiwan has a similar climate. I suggest that the right MC is around 12%, but the most important thing is what glue type you use, because here it is very humid - better to use epoxy.