Boil in the bag steam bending

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A few years ago whilst designing a commission for a study, the client asked if it might be possible to create handles for the cabinets from the same wood being used for the door frames. After throwing around a few sketches, I started looking into how to bend small pieces of wood. There were plenty of videos and articles showing a technique using the microwave. 

This method has the wood soaked in water for 24 hours then wrapped in a wet cloth and placed in the microwave for 30 seconds, whip it out quick and get it into jigs. Frantic.  

The image below was the first prototype made for approval, I like it but the customer wasn’t as keen, so I increased the curve meaning the recess could be removed.  

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Curve increased and this is what made it in to production.  

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Around 60 handles over five or so different jobs, these handles have become a production favourite in the workshop. Using the microwave method worked but had quite a high rate of atrition. I’d maybe need to cut blanks for double the amount of handles needed as some would just snap or split while getting the form, or the spring back made them unusable.  

Mid way through the second batch, I came across a core77 article http://www.core77.com/posts/35838/A-Better-Way-to-Steam-Wood-for-Bending-Use-a-Plastic-Bag and immediately found some extra heavy-duty, lay-flat poly tubing 250 microns thick from Kite Packaging. 

So when making the most recent batch I thought I would take a few pictures, do a little run through of the processes involved in making them. In the past they have been created in Elm, Oak, Ash, and Southern Yellow Pine. 

Material selection is key, I’ve found that to get the best consistency is to try and get as close to quarter sawn as possible, so with the piece of stock pictured below I had to rip a couple of pieces off the block, then rip the strips from them.  

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Strips ripped and then cut to around 300mm to get plenty of room and leverage on the bend. 

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I made a bending jig which has two sides, male and female formers, cutting a piece of the poly tubing with plenty hanging in and out of the jig.  

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We popped the two strips into the sleeve, hooked up a wallpaper stripper and placed tension on the jig with the clamp. Herein lies the beauty of using the ploy sleeve, after around 3-5 mins of steaming you can start to apply more and more pressure to the bend, all the while steam is still running through the set up.  

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Once the form is fully closed the steam can be cut off and the jigs allows to cool. I have three forms to enable a batching of 6 handles per day.  

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Once cooled the outer forms can be removed, the poly sleeve cut away and clamps then reapplied. This is then left overnight to dry.  

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For the final drying they are screwed down to a piece of scrap for as long as possible.  

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A wee trim to length, sanding, rounding over, coat of oil and they’re done.  

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The doors are then routed out from both sides, a longer slot on the back, these ones just need the filler piece in the back.  

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And there you have it. Boil in the bag steam bending.