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Recent Bios FAQ

267295 Charles Driggs 2018‑12‑08 Re: Boutique lumber drying?
Travis, 

Ed, Nathan, & Claudio brought several points into this, but left out at least a
few other factors — what species, where did the tree come from, and how long are
you willing to season the lumber?

The point Ed made with a board standing in a corner for nearly two decades
illustrates two of the three points above — some pieces of wood are just
difficult to dry no matter how you approach it because of their growing
structure or where they grew.  My BIL the forest resources manager (now working
as a timber buyer) showed me the difference years ago between lumber that was
going to be available from two trees a few hundred yards apart — same species,
same plot of land so the same wind, sun, rainfall, and presumably mineral
content in the soil.  One tree was on the edge of a steep hillside, and the
other was on the top of the hillside.  A careful look at the one on the hillside
showed a hint of twisted growth in the trunk, the other appeared to be growing
straight.  Species:  American black cherry.

Twenty five years ago I was working as an investment manager for three projects
which operated sawmills.  Two processed a variety of softwood into construction
lumber, which was dried in steam-heated kilns  We bought at least six different
species of logs, but the least favorite was lodgepole pine.  I didn’t understand
why until we had a shipment of over a hundred logs of lodgepole pine out of a
forest fire from the week before that looked alright in the log yard, cut just
fine in the mill.  But when the kiln was opened after a couple days of the
normal schedule drying for lodgepole, the workers had to struggle to even get
into the building via the man-doors, and the overhead doors wouldn’t open as the
motors tripped out on overload.  The lumber had literally turned into corkscrews
(coil springs if you like), interlocked, and jammed into the kiln building
structure.  It took four days, a dozen workers in two shifts, and a lot of chain
saw maintenance s to get the mess cleaned up.  It was a total loss on that log
buy, cutting costs, cleanup costs, and lost kiln production hours.  We typically
lost 10% of the lumber that was projected to come from a log buy given the
limitations of the optimizing equipment and/or sawyer’s capabilities at
assessing the best way to open the log, but that was an average — some logs
produced lumber that was just crap for reasons unknown because we couldn’t tell
what their growing conditions had been, others had almost no loss of yield at
all.

For furniture grade lumber, or most of what we talk about on the Porch, we’re
talking hardwood, and it can be either air-dryed (preferred) or kiln-dried.  I
have, and I’ll bet quite a few of us on the Porch also have both cut into a
board and had it either bind the saw blade or spread the cut either horizontally
or vertically (visualize: moving your legs in a scissors motion).  I usually
chalk that up to the wood not being either a) fully seasoned or b) from a tree
that wasn’t growing straight on essentially level ground,  but was struggling a
bit because the ground tended to move (slope).  Of course, if we don’t realize
we are cutting up a board from a leaning trunk, we won’t expect to see signs of
reaction wood.  Ship builders in the 17th-19th century looked specifically for
curved logs to produce curved parts for ship hull structures, but furniture
makers normally wouldn’t want any part of them for their purposes.  Unless you
can see the end of the log before your wood is cut, you might not realize it is
coming from a reaction wood log until it starts losing moisture.

What’s my point?  There are many factors to consider when deciding to dry your
own wood, particularly where you do it and for how long.

1.  If you want to air-dry lumber for your own use in a small scale operation,
don’t assume that every piece you process will be usable when it is dry.  If you
get 70-80% of what you start with still usable when you think it is down to the
moisture content you need, you probably are doing fairly well.  Some species
just won’t cooperate with your plans.

2.  Each species dries at its own rate, and there is only so much you can do to
assist it without developing cracks or checks in the material that render it
useless as a full width board.  Ends need to be coated with paint or wax to slow
down moisture loss from exposed the fiber passages; air movement needs to be as
uniform as possible on both sides of the board, but the board may still twist or
warp in ways unwanted, and may never come back to flat.

3.   The board needs to be at a uniform moisture level throughout it’s thickness
and width to be “perfectly stable” — at least in theory, but ambient changes in
humidity are natural and unavoidable.  Changes in seasonal humidity or
differences between shop humidity in the final place of use are of greater
concern, as they can result in fatal cracks in whatever you build.  That can’t
be addressed in initial drying unless you know what the shop and end-use
location humidity conditions are going to be.  Many pieces of furniture from the
18th & 19th centuries didn’t survive being moved into an air conditioned
environment in the 20th C, as it caused fatal joint damage or panel cracking
that destroyed the furniture.

4.   Some of the best known furniture makers in this country (Australia too,
very likely) buy lumber years or decades in advance of it being used — when they
see good material, they bring it in and let it dry naturally.  Why? — to avoid
many of the problems created by trying to accelerate drying of lumber or using
it before it is fully seasoned.  A visit to Sam Maloof’s former residence and
shop with Jim Thompson a decade ago revealed that Maloof had amassed a huge
amount of material that was just sitting there, seasoning away in preparation
for an order that might come many years in the future.

Assume that you may only be able to use half of why you dry as intended, and
you’ll be happy if you can actually utilize a higher percentage of it when the
time comes.  Steel and stone are more uniform in their structure and behavior,
and even they are sometimes unusable as intended.

Charlie Driggs

> Two factors to consider: grain and moisture change.  

Claudio, Ed &

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