Serious wood warping

[Brian Brown]

I got some paper birch after it was freshly cut. I cut and sealed the blanks, and after about a month, I rough turned a couple of the blanks to about 10% of finished dimension. I soaked them in DNA and put them in a paper bag as usual, only this time I filled the bag with shavings and burried the rough outs in the shavings. A month later when I opened the bag the platter and bowl HAD warped and shrunk so much that a re-turn is pointless. Should I have waited longer for the blanks to dry some prior to the rough out, or is this just the nature of birch? If I should have waited, how long? Is there a need to wait a certain length of time with any green wood before roughing?

[charlie knighton]

bowls tend to warp more than some forms, you might want to cut some of the blanks for hollow forms, hf turnings tend to hold the shape better when turned to final thickness and sanding dries the wood

i tuned this maple piece at 35% moisture reading, bleached it, groved it
i did have a crack that was ca'ed, opened up after bleaching, and then it closed up on it's own after several days, it was turned to 3/8 and i am trying to do some spirling but i would just call this a groove instead of a spiral

[Steve Schlumpf]

Brian - I have never turned any paper birch but can't imagine it is that much different than the white birch I do have access to. Only thing you mentioned that is different than what I do is your paper bag method. When I take the blank out of the DNA, I let it surface dry for 15 to 30 minutes and then tightly wrap the outside of the bowl using brown paper bag. The outside and rim of the bowl are completely covered with the paper bag and taped inplace. The inside of the bowl is open and exposed to the air. For storage the bowl is placed on a rack with the opening facing down (paper side up). Make sure that air can circulate around the bowl. Supposedly, the paper retards the drying on the exterior surface while allowing the inside to dry slightly faster. The difference in drying speeds between the two caused the wood to shrink towards the inside. It will warp but with 10% initial thickness you should have enough left to finish turn.

Hope that makes sense.

[Jim Ketron]

Some wood species are just going to move, it’s the nature of the beast!
The only way to help to save a piece with wood like this and to help reduce warping on most species, is to pay close attention to grain patterns in the uncut log before processing .
Try to keep close tight grain patterns and loose grain patterns separated when making your blanks.
You might end up with a small bowl blank and a large bowl blank from one log but less frustration when it comes time to finish your piece.
Here is an example on a log like this, you want to make the cuts on the red lines to keep the tight grain on one blank and the loose grain for the other.
http://i20.photobucket.com/albums/b201/Jim_k/PJRing2-1.jpg
http://i20.photobucket.com/albums/b201/Jim_k/PJRing3.jpg