15 – The Steam Bent Crest

  1. A Walnut Windsor Chair – Introduction
  2. The Log
  3. Transport
  4. Rough Lumber
  5. Seat Blanks
  6. Legs
  7. Arm Posts and Tapered Holes
  8. Carve the Seat
  9. Turn the Undercarriage
  10. Assembling the Seat and Undercarriage
  11. Spindles
  12. Arms
  13. Assembling the Spindles and Arms
  14. Crest Version 1 — The Form Bent Laminated Crest
  15. Crest Version 2 — The Steam Bent Crest
  16. Final Assembly
  17. Detailing
  18. Finishing a Walnut Windsor Chair
  19. Final Notes

Entry 15

Crest Version 2

The Steam Bent Crest  –  1/12/2008

Even though the chairs shown in this blog have laminated crests, I thought it would be interesting to show how I steam bend a crest.  The starting point is a straight grained piece of wood.  The wood is wrapped in a wet towel and left over night.

Steam bending is work (see bottom photo), and you have to work fast.  But, lets start at the beginning.  If the wood is green, it has plenty of moisture in it.  If it has been dried, it does not have adequate moisture.  So, my conditioning step is to wet the wood and place it in a wet (soaking) towel and wrap it up.  It sits for 24 hours which will allow the moisture to penetrate into the surface of the wood.

Now, fire up the steam “box”, shown at the right.  Once it is filled with steam, I place the wood in the box and steam the blank for about 45 minutes.  My steam box is high tech.  I put a coffee can, filled with water, on my Coleman camp stove.  A piece of stove pipe (the box) is on top of the coffee can and an aluminum mesh sits in the water in the coffee can and keeps the wood from sitting in the boiling water.  When the water in the can boils, the steam rises and fills the pipe.  If the blank is a bit too long for the steam box, some aluminum foil on the top keeps the steam from escaping too fast.  I wear insulated gloves and keep my head and arms away from where the steam vents.

When the hot blank is pulled from the box, I have five minutes or less to get it clamped in place on the form.  I use thick blocks of maple scrap to distribute the clamp pressure over the width of the blank as it is clamped to the form.  (The form is made from particle board.)  The first clamp is in the center.  Then a clamp at each end is used to pull (bend) the blank around the form and clamps are put in position every few inches to hold the blank against the form.  Once clamped up, the blank is left in the form to cool and dry.  I leave the blank in the form for at least three days.  When taken out of the form, it will (partly) spring back so the final curve is not as tight as the bending form.  In contrast, the laminated crests hardly spring back at all.  The curve for the steam bending form is tighter (smaller) radius than the lamination form to compensate for this.

I have steam bent maple and walnut crests (both are shown in these photos).  Even though the wood was kiln dried, I have not had any problems when using straight grained wood.  The cherry crests that I have done have all been form bent laminations (done in the winter).  I’ve done one mahogany crest – a form bent lamination.  Mahogany has a reputation as not being steam bendable.

From the standpoint of being a wood worker, both bending processes, steam and a bent lamination, work fine.  Steam bending is certainly the traditional method.  Form bent laminations allow me to bend woods that can not (or at least not easily) be steam bent.  Once the blank is dry and removed from the form, it is drilled, shaped and carved just like the form-bent laminated crest.