Replies

1. 
   JohnWW | Apr 08, 2008 01:02am | #1

   There are kiln schedules, that's there proper name, but they wouldn't do you any good, they are meant for much thicker wood in much larger quantities than you are working with, and they are only useful if you can carefully control air flow and temperature in the kiln and you would have some way to accurately measure the wood's moisture content.

   To be honest while you have wood movement problems it is probably not due to simple loss of moisture but I can't be sure without some additional information.

   First of all, you want the blanks to be at an equilibrium with the air around them, which you should easily be achieving by letting the blanks sit for a month or two after they are sawn to size. At best with a kiln you could get the wood dried to the right point faster but you could easily over dry it and then have to let it absorb moisture to be stable. Kiln drying also doesn't make the wood any more stable than air dried wood.

   Are you stacking the blanks in the same room as your lathe and are they several feet off the floor and stickered? Is the shop or the space they are stacked in especially dry or damp, or is the humidity varying a lot compared to the inside of a home? What is the climate where you live?

   What are the dimensions of the blanks? Is the wood straight grained and split out of the rough stock or are there knots and wild grain in the pieces?

   At what point does the wood movement occur? During the drilling, or the turning or later when the pen is finished?

   John White

1. 
   picapiedra | Apr 08, 2008 01:44am | #2

   Hi John,

   Thanks for your quick answer.  I´m living in Costa Rica at around 90-95% humidity.  Temperature is around 80 F average.  I cut my blanks in about 1" by 1" by 9" long.  I try to stack them in a similar way that you would stack green wood for air drying in a dry table inside of my toolshoop.  Very close to where the lathe is. 

   The srinking happens a few months after I turn the pens.  I use a commercial sealer / finishing product for turned pens.  Here in Costa Rica the pens start cracking after 1 month.   When I send pens to the US ( California ), they srink almost immediately.

   I usually cut my blanks along the grain (easier to turn them this way...).  When I turn them against the grain I get the worse srinking results.  I don´t turn burls or knots or wild grain.  I don´t even want to go there yet....!

   I hope this information is OK for you to make a better assessment.

   By the way, I already bought the kiln, I was wondering if it could still be of any use....

   Thanks for your help,

    

   Mauricio

1. 
   JohnWW | Apr 08, 2008 11:41pm | #3

   Ahhh, you live in paradise, a very humid paradise.What you need to do is get the moisture content of the wood down into the range of 10% to 12%, you're now around 23% MC at 95% relative humidity.If you could store the blanks in an air conditioned space, with a humidity of around 60%, that would be one solution, since air conditioning lowers both the humidity and the temperature in the air. If you can't lower the humidity then you need to raise the temperature of the air, which is what your kiln can do.

   The easiest thing to do is get a moisture meter that will measure the moisture content of the wood. For your purposes a small prong type of meter is the better choice. Once you have a meter, stack your wood in the kiln and run it at 140 degrees Fahrenheit for a few days until the MC on the meter stops dropping. Measure the MC at the midpoint of the blank to get a good reading. At that point the MC will be lower but probably not down to 12%, so you should raise the temperature by another 10 to 20 degrees and measure again in few days. Keep measuring and raising the temperature until you hit the desired 12% MC or a bit less. My guess is that you'll have to be around 180 degrees to get to the 12% MC point when starting with 95% humidity incoming air, but that's just a gut feeling.Drying wood quickly creates stresses that can make it unusable so you'll probably have to increase the temperature in stages and be sure to seal the end grain to prevent end checks from forming. Once you get to the 12% MC you will either have to keep the wood at that temperature or seal it in an airtight wrapping. If you leave it exposed to the surrounding air it will reabsorb moisture and you'll be back at the 23% MC in a few days, but the meter will help you to get a feel for what is happening.I suspect that when you turn the blanks, the thin shells will absorb moisture very quickly from the air so your efforts at drying the blanks may not have any practical effect. The best approach will be to drill the blank and get it on the tube as quickly as possible and then to either turn it down immediately or return it to the kiln environment as needed to bring the moisture content back down. Once the pieces are done and finished, the blanks will absorb moisture from the local air and expand slightly which hopefully won't cause stresses that create new problems.Good Luck, John White

1. 
   picapiedra | Apr 08, 2008 11:52pm | #4

   John,

   Thank you very much for your practical approach!  I will put it in practice immediatelly and I'll be reporting my results!

    

   thanks again,

    

   Mauricio

1. 
   JohnWW | Apr 09, 2008 12:22am | #5

   Glad I could help, hope it works. Do you glue the tubes into the wood? If you don't you may find that they get loose when the wood expands after the pen is finished. I'm not that familiar with pen making so this question may not apply.John W.

2. 
   picapiedra | Apr 09, 2008 12:32am | #6

   John,

   First I drill the blanks, and then I glue the blanks to bronze tubes with CA Glue or epoxy.    Then I turn them and finish the final product on the lathe.

   Thanks,

   Mauricio

3. 
   saschafer | Apr 09, 2008 01:15am | #7

   When you say that the wood shrinks, what exactly are you seeing? Is the wood cracking? My guess is that if you dry the wood as John suggests, then do the drilling, gluing and at least the rough turning all within a short time (less than a day), you'll be fine.

   Pura vida,

   -Steve

    

4. 
   picapiedra | Apr 09, 2008 01:28pm | #8

   Hi Steve,

   It´s nice to know that you know about my country!  Pura vida is pretty costa rican :)

   What I see is this:

   1. In thin pens I see cracks that start at the thickest end and go along to the center of the pen.  These cracks are usually less than 1/4" long.

   2. In thick pens, I see a total reduction in the dimension of the blank, leaving a gap of about 1/32".

   I´ll follow your advise of doing this in less than a day and producing in small batches for the day.  I´ll let you guys know the results.

   Thanks,

   Mauricio

5. 
   saschafer | Apr 09, 2008 03:52pm | #9

   If you drill a hole in the wet wood, then as the wood dries, the hole tries to become smaller in diameter. But after you've inserted the metal tube, the hole can't get any smaller, and I think that's what's causing the cracks. If you dry the wood before drilling the hole, that shouldn't happen.

   My wife and I have been to Costa Rica on birding trips three times, for a total of about seven weeks. Where in Costa Rica are you located?

   -Steve

    

6. 
   picapiedra | Apr 14, 2008 03:45pm | #10

   Hi Steve!

   I live here and I've never been to a bird watching tour!   I live in San Jose, the capital.  Please send me a mail whenever you get around here again.

   Best Regards,

   Mauricio

7. 
   saschafer | Apr 14, 2008 04:14pm | #11

   For shame! You should at least take a day trip down to Reserva Carara (on the coast near Tárcoles) and see the Scarlet Macaws.

   -Steve