I am importing turned wood products frpm Central America - Some of the
products form bad cracks some do not - these are substantial pieces
some as thick as 5/8". What can we do to avoid crackiing. Should we be
Klin Drying before we turn - and then dry the some more?

Your question led me to your web site. While totally off the point, I
notice that you are importing something you are calling Brazilian
Rosewood. You may or may not be aware, but it is illegal to saw the
true Brazilian rosewood (dalbergia stevensonii), world-wide. The wood
you are dealing with is usually called Jatoba or Brazilian cherry. It
doesn't have the mystique of 'rosewood' but changing the name just might
keep the feds off your doorstep.

Now, to your question.

In Belize, the humidity is normally much higher than here and they don't
have the cold weather and heated houses to deal with. When you move a
piece which was turned green or partially green from Belize to the US,
you are going to have problems.

The 5/8" thickness adds to the problem -- thinner would be better. In
any event, though, there are some basics you must consider.

Cocobolo and related woods are very slow to give up water. The pieces
probably are going to have to be rough turned, kiln dried very carefully
and then re-turned. Without a doubt, that drives your production cost
and lead times up, even in Belize.

At the risk of offending, it seems to me that there are some pretty
basic things of which you are not aware when it comes to wood and
turning. I wish you the best but I think you need some expert advice
somewhere along the line. I'm no expert but I have spent a lot of time
in Belize, southern Mexico and Guatemala buying logs and lumber. If you
want to take this conversation off line, let me know. Also, I'm
guessing that I may know your source down there.

Bill

wrote:
I am importing turned wood products frpm Central America - Some of the
products form bad cracks some do not - these are substantial pieces
some as thick as 5/8". What can we do to avoid crackiing. Should we be
Klin Drying before we turn - and then dry the some more?

On Thu, 05 Jan 2006 16:07:34 GMT, Bill Rubenstein
wrote:

The wood
you are dealing with is usually called Jatoba or Brazilian cherry. It
doesn't have the mystique of 'rosewood' but changing the name just might
keep the feds off your doorstep.

Now, to your question.

All the other things you had to say aside, and having turned no small
amount of jatoba myself, it is my personal opinion that they would do
just as well to turn domestic apple wood, as far as stability goes.
That may be a _bit_ of an exageration, but only a bit. For its
density and __apparent__ dryness (as opposed to the obvious
oily/dampness of most cocobolo you see, for instance) jatoba is
rediculously unstable and apparently incapable of retaining its
finished shape.

Best bet: either find another, more stable wood or rough turn let dry
or kiln dry or microwave dry and then finish turn. Keeping your
fingers crossed the whole time, of course.

At the risk of offending, it seems to me that there are some pretty
basic things of which you are not aware when it comes to wood and
turning.

Absolutely. But you know, I have a friend in the lumber business who
runs into the same thing. He buys stuff that is supposed to be kiln
dried yet when he gets it indoors -- and even turning stock that is
immediately Anchor-sealed -- he starts losing stock to checking.
Personally, I would find a new buyer. But I digress...

I wish you the best but I think you need some expert advice
somewhere along the line. I'm no expert but I have spent a lot of time
in Belize, southern Mexico and Guatemala buying logs and lumber. If you
want to take this conversation off line, let me know.

Heavens no! Don't take it offline. This is precisely the sort of
thing that helps this newsgroup expand its horizons beyond the latest
tool knockoff or discussions of household cleansers and wood drying.
While probably most turners haven't yet turned a wide range of
exotics, most probably hope to at some point, and it is exactly this
sort of forum that helps people expand their knowledge base and know
what to expect when they do get that opportunity. Nothing more
frustrating than getting all excited about turning your first piece of
cocobolo, making a nice, suction fit box and a week later having to
actually _saw_ the pieces apart because they're so tight together. Or
making a platter out of a nice wide piece of jatoba and a month later
it looks like a Pringles potato chip...




--
Chuck *#:^)
chaz3913(AT)yahoo(DOT)com
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"Bill Rubenstein" wrote in message
om...
Now, to your question.

In Belize, the humidity is normally much higher than here and they don't
have the cold weather and heated houses to deal with. When you move a
piece which was turned green or partially green from Belize to the US, you
are going to have problems.

The 5/8" thickness adds to the problem -- thinner would be better. In any
event, though, there are some basics you must consider.


Well, no. Not necessarily. Wood has a certain moisture content with
respect to the relative humidity regardless of the location. If the piece
is turned in Belize and reaches EMC at 80% RH, it can go anywhere 80% exists
without a problem. Don't know how long the turning waits for shipment, but
if it stabilized, it certainly is not geography which splits it.

As to thickness. It is the orientation and spacing of the annual rings,
not the thickness that determines direction and dimension of deformation. I
think of the turnings and carvings my squadron brought back from Southeast
Asia which never split indoors in a North Dakota winter as an example.

I'm going with the nature of the wood. Of course the OP can determine
what's at fault by taking a piece at EMC with Belize outdoor and warming or
drying it slowly to ~60% RH, a good all-round place to begin for inland
areas.

Your point about orientation and spacing of the annual rings is right
on. But, one of the problems with very dense woods like Cocobolo is
that they do not willingly give up water in any direction, not even
through end grain. So, you get the shell dry (especially if you force
it by too-quick kiln drying or nuking it) and the interior wet. Then
the shell takes a set. When the center of the piece begins to give up
water, finally, the shell cannot shrink and you have honeycomb -- the
structure of the wood destructs from the inside out.

The box makers who use exotics (and most who don't) rough turn boxes,
dry them carefully, and then finish turn. I suspect that the three step
approach might be reasonable with certain nasty woods.

Anyway, with cocobolo you would want the walls to be thinner so that the
moisture gradient between the shell and the core of the piece would be
less of a problem than if the piece were thicker.

I've designed and built kiln drying equipment for cocobolo and a light
touch is called for. Just extracting water is a guaranteed way to fail.
You have to keep the shell from giving up moisture as quickly as it
would like to in order to keep the gradient down. So, in my opinion,
kiln drying cocobolo requires adding moisture to the air in the kiln to
keep the humidity up and to keep the drying time long.

BTW, another reason for wanting thinner walls with cocobolo -- the stuff
is so damned heavy! I sure do love it, though.

Bill

George wrote:
"Bill Rubenstein" wrote in message
om...

Now, to your question.

In Belize, the humidity is normally much higher than here and they don't
have the cold weather and heated houses to deal with. When you move a
piece which was turned green or partially green from Belize to the US, you
are going to have problems.

The 5/8" thickness adds to the problem -- thinner would be better. In any
event, though, there are some basics you must consider.



Well, no. Not necessarily. Wood has a certain moisture content with
respect to the relative humidity regardless of the location. If the piece
is turned in Belize and reaches EMC at 80% RH, it can go anywhere 80% exists
without a problem. Don't know how long the turning waits for shipment, but
if it stabilized, it certainly is not geography which splits it.

As to thickness. It is the orientation and spacing of the annual rings,
not the thickness that determines direction and dimension of deformation. I
think of the turnings and carvings my squadron brought back from Southeast
Asia which never split indoors in a North Dakota winter as an example.

I'm going with the nature of the wood. Of course the OP can determine
what's at fault by taking a piece at EMC with Belize outdoor and warming or
drying it slowly to ~60% RH, a good all-round place to begin for inland
areas.

(Chuck) wrote:

Or
making a platter out of a nice wide piece of jatoba and a month later
it looks like a Pringles potato chip...


Then it is Art.