Drying rough turned bowls
 

I am presently rough turning some green bowls and I need to dry them
without checking. I understand the wall thickness should be about 10%
of the diameter of the bowl and that I have to control the drying rate.
I believe this can be done by placing the bowls in a cardboard box and
setting it aside for a few months. What I am not sure of is how the
bowls have to be packed in the box, how much airspace they need or if
small pieces like under five inch diameter need to be packed at all.
Any information and hints on curing this green wood before finish
turning would be helpfull. Thanks Rod

wrote in message
oups.com...
I am presently rough turning some green bowls and I need to dry them
without checking. I understand the wall thickness should be about 10%
of the diameter of the bowl and that I have to control the drying rate.
I believe this can be done by placing the bowls in a cardboard box and
setting it aside for a few months. What I am not sure of is how the
bowls have to be packed in the box, how much airspace they need or if
small pieces like under five inch diameter need to be packed at all.
Any information and hints on curing this green wood before finish
turning would be helpfull. Thanks Rod


Perpetual question. My recommendation is to take a look at
http://www.fpl.fs.fed.us/documnts/fp.../fplgtr113.htm especially
chapters two and three. That'll give you a good handle on how wood dries.

A reply to someone growing hairy mildew on one turning , posted by me,
recalls the two important moisture content levels. Until the unbound water
(the stuff that hits the wall when you turn) is gone, leaving the wood at
~30% moisture, no fiber collapse due to dehydration takes place. This is
not to say that there isn't a difference between inner and out. Indeed,
control of this gradient is what drying is about. But feel free to fling
all the water you can, and wait for the surface to look dry before putting
the piece into a controlled environment.

The second figure is ~20% moisture content, where nasty black mildew, which
leaves lasting stains, doesn't grow. So bag, coat, or wrap as desired once
the surface seems dry, though you might want to just leave it alone if
you've a fairly high RH. Stay ahead of mildew with ventilation and
rewrapping as required.

Oh yes, when you look at the information suggested, take a look at the
volumetric shrinkage rates, then use them and your desired wall thickness to
determine how thick to leave a blank. Thicker it is, longer it takes, and
it doesn't seem linear.

Rod
You may want to check out my web site as to how I handle rough turned bowls.
There is nothing new there, just the tired and true method that a lot of us
used for thousands of bowls.

--
God bless and safe turning
Darrell Feltmate
Truro, NS Canada
www.aroundthewoods.com

Thanks for the information. Very informative wood site that you
recomended
George wrote:
wrote in message
oups.com...
I am presently rough turning some green bowls and I need to dry
them
without checking. I understand the wall thickness should be about
10%
of the diameter of the bowl and that I have to control the drying
rate.
I believe this can be done by placing the bowls in a cardboard box
and
setting it aside for a few months. What I am not sure of is how
the
bowls have to be packed in the box, how much airspace they need or
if
small pieces like under five inch diameter need to be packed at
all.
Any information and hints on curing this green wood before finish
turning would be helpfull. Thanks Rod


Perpetual question. My recommendation is to take a look at
http://www.fpl.fs.fed.us/documnts/fp.../fplgtr113.htm
especially
chapters two and three. That'll give you a good handle on how wood
dries.

A reply to someone growing hairy mildew on one turning , posted by
me,
recalls the two important moisture content levels. Until the unbound
water
(the stuff that hits the wall when you turn) is gone, leaving the
wood at
~30% moisture, no fiber collapse due to dehydration takes place.
This is
not to say that there isn't a difference between inner and out.
Indeed,
control of this gradient is what drying is about. But feel free to
fling
all the water you can, and wait for the surface to look dry before
putting
the piece into a controlled environment.

The second figure is ~20% moisture content, where nasty black mildew,
which
leaves lasting stains, doesn't grow. So bag, coat, or wrap as
desired once
the surface seems dry, though you might want to just leave it alone
if
you've a fairly high RH. Stay ahead of mildew with ventilation and
rewrapping as required.

Oh yes, when you look at the information suggested, take a look at
the
volumetric shrinkage rates, then use them and your desired wall
thickness to
determine how thick to leave a blank. Thicker it is, longer it
takes, and
it doesn't seem linear.

Thank you for the help. You have a very interesting website that I
will probably link up to from time to time. I am fairly new at serious
woodturning but I have a wealth of material, mostly birch, tamarac,
poplar and manitoba maple available as I live in northern Saskatchewan.
Thanks again
Rod