For this relatively simple operation, I usea stainless-steel kettle because it eliminates the reaction of tannic acids in the wood with the iron (photo I). I start with rough blanks that are approximately 3/8x4x20", totally submerging them in boiling water until they're flexible enough to bend easily -- usually about 15 minutes. I do the initial bending on a form, then dry them under tension on a rack (photo J).
You can use kiln-dried, air-dried, or green wood for bending. I find kiln-dried stock tends to be brittle, but overnight pre-soaking in cold water seems to help. Green wood can be bent with less heat, but it tends to be unstable unless I let it dry completely in the racks. I prefer air-dried lumber for this purpose. It doesn't break or splinter as readily as kiln-dried wood, yet it dries more quickly than green wood -- within a week or two, depending on the temperature and humidity. When the slats shrink enough that they no longer fit tightly in the rack, they're dry enough to be worked.
I match a set of slats for each chair by grain and color, then pilot-drill and nail them together, keeping the nails in the waste areas (photo K). Next, I straighten the bottom edge of the stacked set on the jointer (photo L). I crosscut both ends to length, which, because of the curvature and stacking, makes each slat slightly shorter than the next one down in the stack. Using a pattern, I trace the slat outline onto the top face, then bandsaw the curved top edge of the stacked slats with a single saw cut.
