Construct a wooden box about 7 feet long by 1 foot wide by 1 foot high. Along the inside bottom of the box, place a copper pipe that has been riddled with perforations. The pipe should exit the box via a "T" junction near the centre. Where this "T" junction pokes out of the bottom of the box, attach one end of a PVC flexible hose. Attach the other end of the hose to your steam source (we used a regular electric kettle, but a modified pressure cooker or a steam machine, like a wallpaper steamer, would have been more ideal. Kettles constantly have to be refilled, can be hazardous to use and tend to burn out). Also, fasten little pieces of wood to the inside bottom of the box so that the plank to be steamed can rest on them, thereby leaving room for the steam to get under it.
(Note: I have received several suggestions regarding simpler ways to build a steam-box. Some people suggest using a large diameter PVC pipe or a length of aluminum duct instead of a wooden box. If you choose this method, then wires can be run width-wise through the 'steam-box' at intervals to serve as rests for the plank you are going to steam. These rests will allow the plank to be suspended so that steam can fully surround it. One end of the pipe or duct must be capped and the other end left open. When in use, the 'steam-box' must be set on a slight incline so that the capped end is higher than the open end. Place the steam source at the open end so that the chamber can fill with steam.)
Click here to see detailed plans for a wooden steam box
Click Here to see a picture of a PVC steam box
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