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Steaming wood to prevent warping and cracks?

S

squirrel

Joined
Sep 27, 2007
Messages
132
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Location
Belgium
Hi guys!

I often boil my preturned bowls to make the drying time shorter and to prevent splitting, warping and cracks. i'm satisfied about this method.
But !!! For the moment I'm turning bowls which measure about 28 inches diameter. Also the final design makes ( I have to do sculpture on these) that I have to leave them very thick 2 - 3 inches).
Consequence: .I cannot boil them because I do not have a pot which is so big
. Because the piece of wood is so huge, there is a lot of risks
that it makes cracks and splits during the drying process.
. It will take much too much time to let them dry 'naturally'.

I am thinking about a system to solve my problem because I want to finish the turning in march - april 2011 and not in two years!! (The wood was cut october 2009. The wood is Lime.

If I make a wooden box with a hole in the bottop and I place my bowl inside the closed box. Then a fill a pot with water, place it under the hole in the bottom of the box and boil it. All the steam has to enter the wooden box.

Do you think this will have the same effect on the wood as boiling will do?
I mean: will the 'liquid' in the grain of the wood be replaced by the hot water? If this is true, then it can be a solution for me to preserve better my big pots (of course I will cover them afterwards to make let them dry slowly)
without having to buy (expensive) or find huge pots and spend a lot of money on heating.

I also remember that a while ago, there were some threads about people who build a heating chamber by putting light bulbs in a wooden box. How is it possible that there wood does not split? I thought slow drying was a must?

Thanks for your reply - Squirrel
 
Preventing Cracks in Bowls

I use the LDD soap mixture that Robo Hippy said in your other post, most of the time. It works well and I really think it helps to prevent cracks from re-wetting the wood after turning. But the other idea that Reed aka Robo Hippy had mentioned is the double wrap of a 6" wide shipping "saran wrap" around the rim. then upside down on a concrete floor for a few hours , then double bag and keep close to a concrete floor until dry. I have had no cracks with this method. Sometimes the wood is configured to help cause cracks and some of those you can see while turning are still minimalized. I have only used these methods to 22" Dia with a 3/4" wall.

Good Luck,

Dave
 
All of the fancy "solutions" have less effect than the shape of the object itself. Deep and steep is the worst at cracking, with possibilities of cracks pretty much eliminated by the time you get to a 50 degree average wall angle when the heart is up.

That said, our American Basswood - the brother of your lime - is almost bulletproof in drying. Don't steam it or fuss over it. Rough to about 10-15mm over the thickness of desired dry walls and dry it fairly rapidly to prevent mildew. Unheated shed this time of year would be great. After the first three or four weeks you can bring it in to a space where the humidity is a human-friendly 55% or greater for the last six to eight. Weigh to confirm, but it should be ready to go at ~three months if it's bowl-shaped.
 
I think if you are fine with boiling, I would stick with it. If it's just a container that is a problem check for used 55 gal drums to cut up or an old wok or BBQ. I'll bet you could pick up a BBQ along the road or thrift store. I use the boil method also and like it most of the time. Steven Russell has a great write up on it and also the process the wood goes through which might help answer your question on Steam. His site is woodturningvideosplus dot com.
 
Sivad Selim

Hi Squirrel,

You could go to a witch's going-out-of-business sale and make an offer on the cauldron. Or you could locate a converted tribe of cannibals and ask them for the large cook pot they no longer use. The end of a large propane tank could also be used as a container for boiling.

I think the idea of steaming in a wood box is worthy of testing.
 
Robert Manning said:
Hi Squirrel,

You could go to a witch's going-out-of-business sale and make an offer on the cauldron. Or you could locate a converted tribe of cannibals and ask them for the large cook pot they no longer use. The end of a large propane tank could also be used as a container for boiling.

.
Click to expand...

Or you could steal Grandma's old Speed Queen wash machine. It has a stainless steel tub that with a little modification would work well.😀
 
What about an old wash tub. I am not sure how much volume you want to boil up at one time. But an old wash tub would have the diameter. It does not have to be stainless steel.
Hugh
 
Not to belabor the obvious, especially as this has diverged delightfully, but soaking wood to speed drying is like fighting for peace. Makes no sense.

Boiling and steaming from without will loosen up the lignin to relieve inner tensions in the wood. I have even squeezed wood back toward round in its plastic state, though the wood in question was only 1/4" thick, so it was actually possible. Steaming from within will not only relieve some growth tension - not drying tensions - but it will actually drive moisture from the wood. Sometimes the result is unattractive, as the extractives follow the line of least resistance and make waterspots on the exterior. That's done in the microwave. None of the methods will modify the standard drying shrink direction or extent. That's in the shape of the piece and the curvature of the annual rings.

Not sure anyone besides myself has ever worked bass/linden/lime, but it has next to no resistance to mold and mildew, and is prone to turn brown in the large within a warm month or two. Blotches in a not particularly attractive way. Get the shape reduced so drying can begin soon, Squirrel, and move the drying through ~18% fairly rapidly to avoid black mildew spots.
 
boiling versus drying in a kiln

Hello,


I believe in boiling - short time - or I also believe in laying the wood in the (rain)water - long time. My experience is that the wood does not crack so often and also that the warping is less than when you dry the wood without replacing the lignin or a part of it by water. It is a medieval method - it proofed that it makes sense.

I did not think about taking a bath to boil the bowl! A wonderfull idea - cheap and not much work compared to other usefull solutions. Thanks!
It is also less work than steaming, which will force me to make a special box and so on.

The reason I was thinking on steaming to releave internal stress is because the 2 - 3 inches wallthickness is not so common. I need this roughturned thickness because my final model will be sculpted. I thought that steamed water would (maybe) enter deeper in the thick, roughturned wood and also it was a solution for the big soup cauldron that I could not find secondhand. I think steaming must have the same effect on stressrelieve as boiling has.
But ok, I'll go for boiling (again) in a bath.

What I do not understand!!!!! Is this strange kind of opposal information:
1. there are all kinds of documentary about how to dry wood, cooking , impregnation, all kinds of wrapping , slow air drying.... all solutions which work prett well ... and on the other hand: there is a lot of information to find about how to dry preturned wood in a kiln!!!! No impregnation, no warping .... and all at once there seems not to be any problem with splitting, tensions, cracks and so on. I really cannot understand this. Or does it depend on the kind of timber? Or isit only used by people who lives in areas where there is a lot of humidity or who have not enough heated space to get them dry in cold wintertimes, so they slightly speed up a bit by putting it in a soft and constant , slowly drying environment?

Squirrel

What I think a good solution can be is first to boil it, turn it upside down for a while and cover the back and then after a couple of weeks put it in a kiln or in a room at roomtemperature. I would put it eventually in a kiln but I think it is dangerous to put air in the kiln as well because it will give surface splittings. No? A kiln not more than 100 degrees and no wind is my opinion or room temperature (and no wind either).

.
 
by the way ...

I forgot to tell you that the wood was in my garage for one year and does not have blotches or whatever. I do not think it will bleed when it is boiled and our European Lime is a nice wood to turn but is not so dull that it does not warp or split. I have some pieces in my garage 40 inches wide and they split all along the piece, precisely in the middle - a pity! The wood was treated with an anti-split product.
Squirrel
 
Lignin is not water-soluble. It will creep when heated and under stress. It takes boiling the macerated pulp in caustic soda to remove lignin in papermaking.

When you examine all the conflicting information on drying, you should draw the obvious conclusion that nothing in any of the individual methods does the job, rather there is something shared by all which is responsible. In simple fact, moisture evaporates and is carried away in the air in ALL of the methods. Simple as that. You can add energy to the process to speed the escape of energized water molecules into the air, remove moisture from the air to allow it to take up more or increase air exchange to carry away more. If you want to get data, not anecdotes, try this URL. http://www.fpl.fs.fed.us/products/publications/several_pubs.php?grouping_id=100&header_id=p The pertinent chapters are part of chapter three and all of four.

Why aren't turned pieces kilned? There is not enough value added by shortening normal drying times. A pre-turned piece will dry to EMC in much less time than a plank of equal overall thickness, as well.

Glad you didn't get the browning that is so common with our Tilia sp. when left in the log. It's not attractive. I think it's a nice wood for salad or popcorn bowls. http://i35.photobucket.com/albums/d160/GoodOnesGone/a06f7f94.jpg

For carving, it's as friendly as can be. Butternut might be better overall, but it's not normally available in such sizes as bass.
 
OK- I can see Tilia is much more orange than Lime is. lime is nearly white and stays nearly white. The pattern is very soft, a bit misty - nor especially what woodturners like but I like it.
Thanks for the picture - i don't have photographs of mineI'm afraid because I do not have a camera nor a mobile with a camera.
Squirrel
 
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