Whether insulation is worth the trouble depends on where and how you're going to use the box. I don't insulate mine at all, but I mostly use it to steam relatively thin wood (as your project demands), so I don't need terribly long times in the box . If you're going to bend 1.5" wood, you'll need at least an hour in the box as Bradley says, but 10 minutes in live steam will completely "melt" a 1/8" lam strip. Takes somewhat longer if you load a big box up with many such strips, but still, you're talking less than 30 minutes.Originally Posted by Alan Lightstone
Also, understand that if you insulate a plywood steam box well on the outside, you are going to break down the plywood over multiple heating cycles. You're basically guaranteeing that the plywood will be reaching steam temperature almost as quickly as your bending wood does, and that it's going through extreme moisture content cycles. Even exterior grade off the shelf plywoood is not designed for repeated cycles of 200oF temperature cycles.
My advice - do a test run on one or two strips of wood of the thickness your target material is. Bring the box up to temperature, put your wood in, and check after 15 minutes, then again after 20+. You'll likely find strips of the sort you're doing are in great shape to bend.
If you do find yourself in cycles where the Earlex is running low, keep a thermos of very hot (boiling when poured) water at hand. You can top off the Earlex when it gets low, and recovery time for steam will be very low. If you feel some insulation would be of help, you can probably find a cheap thermal blanket at a used household good store, or pickup up a thinsulate camping blanket you can wrap around your box.
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