Reply by JAAune

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Posted on Need some advice

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1788 posts in 2282 days

#1 posted 11-20-2012 02:56 AM

I don’t seal my steam boxes nor do the others I know who do steam bending. As MBS indicates, wood finishes won’t hold up under the harsh conditions the box will be subjected to. Also (in case you don’t already know), don’t pressurize the box. Steam pressure is dangerous and doesn’t help the bending process any (unless you’re at high altitudes and need pressure to reach temperature). You just need a heat source around 200-212 degrees fahrenhiet that won’t dry out the wood. Steam does that job well.

There may be some coatings such as epoxy finishes that will completely sealing the wood but I wouldn’t count on that. Even if the coating is completely water-proof it may develop cracks at some point that will admit moisture. The downside to applying finish to the wood is that finish acts as a moisture barrier both ways. Once the finished wood gets wet it will take forever to dry out.

I suggest a cheap, exterior grade plywood without any caulk, sealer or finish of any type. Assemble it with some deck screws. When the steaming operation is done, open the box and let everything air dry before storing. Not only is such a box fast and cheap to make, but it will hold up for years before it needs replacing.

47.5”x18”x8” is a very large box. Hopefully your steam source is up to task. If you really need one that big then build it but otherwise, keep it as small as possible. Having two or three boxes of different sizes for different jobs is also a good idea.

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