How to Make a Quick Kiln
When I released my Compwood arm bows
from the clamps this morning, I saw a little bit of springback. It was
less than I’d get with other bending techniques, but it was more than I
I had expected zero springback.
When Chicago furniture
maker Jeff Miller had introduced me to the material, he said that he was
impressed because the material kept its shape perfectly after it was
dry. So I started to dig a bit.
I called Miller this morning and
chatted about the species he was using, the type of bend and how he
dried the wood. Miller said he was bending pieces of ash that were 8/4
thick and 5″ wide – and bending them on the 8/4 dimension. The radius of
the bend was about 20″ – this was a shape useful for a chair back.
bending the wood, which took so much effort that it eventually busted
the form, Miller dried the wood in a shop-made kiln. He made the “kiln”
using loosely assembled 2″-thick pink foam insulating boards from a home
center. And he heated the kiln using a ceramic heater that had a fan.
After leaving it in the kiln for a week, Miller removed the Compwood from the form.
“It was pretty much flawless as far as springback is concerned,” Miller said.
I decided to talk to Chris Mroz at Fluted Beams LLC, the company that
makes and sells Compwood here in the Americas. Mroz purchased the burly
press that compresses the wood in length, which makes the wood flexible
when it is cold.
Mroz said that working that press is equal
parts art and science – so much so that it took him a couple years to
master the process and that he still compresses every piece personally.
to drying Compwood, Mroz recommends a kiln made from insulating foam
that can maintain the temperature at 100° to 110° Fahrenheit. He has
used ceramic heaters with fans, but says they tend to burn out quickly.
Now he uses radiant dish heaters and places a fan directly at the work.
to timing, Mroz said he would dry a piece that was 1-1/8″ thick for
about six days. If the piece were just sitting out in the form – no kiln
– he would let it sit for two to three weeks.
But what about my moisture meter readings? Our pinless moisture meter said the wood was at 7 percent.
said that pinless meters tend to measure surface moisture for the most
part. His guess is that the wood was still wet at the core but dry on
So it sounds like my arm bows might still be a bit
wet. I clamped them both back in the form and will head off to the home
center to get some foam.
— Christopher Schwarz