Drying question (Pic added)

[Christopher K. Hartley]

I gave a roughed out walnut bowl the DNA bath and wrapped it just like the instructions that Dennis gave in his tutorial. I went and unrapped today and a number of hairline cracks and some larger ones had developed on both sides of the bowl accross from each other. a couple were big enough that I used thick CA and walnut dust to fill the cracks hoping to stop them from getting bigger, the rest I ran thin CA into. Am I doing something wrong in the drying process or is this just something that happens every so often? Any Thoughts?:( The size is 9 1/2" X 4".

[Raymond Overman]

Was the pith of the tree running through the bowl? Was the area you stored your roughed blank at a fairly constant temperature? Was there any air currents around where you stored your blank? Was the thickness of the roughed turning consistent throughout the piece and about 1/10 the diameter of the bowl?

All of these could be a factor in the roughed piece cracking or it could just be bad luck. It sounds like you were able to salvage the blank. Good luck with the rest of the process.

[Christopher K. Hartley]

Was the pith of the tree running through the bowl? Was the area you stored your roughed blank at a fairly constant temperature? Was there any air currents around where you stored your blank? Was the thickness of the roughed turning consistent throughout the piece and about 1/10 the diameter of the bowl?

All of these could be a factor in the roughed piece cracking or it could just be bad luck. It sounds like you were able to salvage the blank. Good luck with the rest of the process.

All of these are things I will make note of thank you. I show the bowl when it is finished. I never thought about the consistancy of the walls throughout the piece. I rough turned with some form and that could be the problem.

[Reed Gray]

I have found out that no matter which drying method that I am using, be it air, LDD, or DNA, when the drying is controled (slow, in cool, humid place) the cracks that do appear are usually there before I start drying. Any crack that is there will get bigger as the blank dries. Almost every tree has some cracks off of the pith to start with. I have also found out that if the tree has been down for a year or two before cutting up and turning, they will tend to crack more than fresh wood, sometimes opining up as you turn. Walnut is generally more stable than most other woods, but because of the color, the cracks aren't as visible as in a lighter wood.
robo hippy

[Reed Gray]

I have found out that no matter which drying method that I am using, be it air, LDD, or DNA, when the drying is controled (slow, in cool, humid place) the cracks that do appear are usually there before I start drying. Any crack that is there will get bigger as the blank dries. Almost every tree has some cracks off of the pith to start with. I have also found out that if the tree has been down for a year or two before cutting up and turning, they will tend to crack more than fresh wood, sometimes opening up as you turn. Walnut is generally more stable than most other woods, but because of the color, the cracks aren't as visible as in a lighter wood.
robo hippy

[John Hart]

Chris...I think you can safely expect about 25% losses no matter what. Although, that is significantly better than just drying. Now, this boiling method that Robert Mickley and Jim King use...I'm hearing better than 90% success. Seems worth a try. After our move, I'm going to rig up a giant pot of water.;)

[Raymond Overman]

Now, this boiling method that Robert Mickley and Jim King use...I'm hearing better than 90% success. Seems worth a try. After our move, I'm going to rig up a giant pot of water.;)

I've got a pro-turner friend of mine that boils everything. He still has about as many cracks in pieces that I do using the DNA method. He also has tried the dish soap method and has a nice kiln with a dehumidifier and thermostat tacked on to the back of his house. He's run the gambit of processes trying to find the solution.

Not to discourage, but sometimes I think it's just a crap shoot with some species. Fruitwoods for example pose a problem for me. Especially during the hot summer months.

I think the key is to get enough blanks in the pipeline completely coated with anchor seal and placed in a cool place with no air circulation that they dry extremely slowly. The problem is, we're not patient enough to wait for them to dry slowly. Of course my opinion is worth .10 if you tape a quarter to it and I'll keep trying the alchemy.

I wrote some articles a while back on the various methods of drying wood. You can find it in the Articles & News section of my web site under "Giving a Bowl a Drink", "More On Drying Wood", and "Even More Drying". There's nothing new there and I can't take credit for the methods. I just compiled all of the things I've read about and discussed them from my point of view. Hopefully this isn't against the TOS but I think it's timely for this discussion. http://www.overmanshop.com

[Christopher K. Hartley]

Thanks for the info guys. I'll just keep keeping on!:)

[Bernie Weishapl]

I have found and don't know if there is any merit to it that if I wrap fruitwood in a couple of layers of newspaper with the bowl part open I get a lot of cracks. If I wrap them in a brown grocery sack leaving to bowl part open I don't have as many crack. So I use brown grocery sacks now most of the time. I am just wondering if using the heavier brown paper makes it dry more slowy?

[John Hart]

I've got a pro-turner friend of mine that boils everything. He still has about as many cracks in pieces that I do using the DNA method. ....

I'd be interested to know how long your friend boils his pieces Raymond. I really don't have much hands-on experience so I really can't dispute anything....but I remember someone telling me to boil for 45 minutes and that seemed kinda short. Robert Mickley boils for much longer and does lots of bowls at the same time. Jim King has said 4 hours.

Here's another data point....I was reading the other day about the art of Kiln drying because I'd like to build a kiln after we move. In one of the articles, I read that the secret to successful drying is down at the cellular level on the wood....that the wood is at its maximum strength when the cell wall becomes hardened. This got me to thinking about Jim King's 4 hours. Maybe he is cooking the wood into a harder state by forcing the cell walls to become hardened.

All speculation on my part at this point...but I sure would like to find the secret.:)

[Raymond Overman]

John,

I'll have to ask him about the time he boils them. As for the science around it, I think it has to do with increasing the elasticity of the fibers in the wood. It's similar to the process of steaming wood to bend it.

I'm no scientist but here are a couple of things to think about. When you boil the wood, the water in the cells of the wood expand. The expansion breaks the cell and allows the moisture to escape more rapidly than it would through normal osmosis. It also leaves the cell in an elastic state because the pressure build up stretched it at the cellular level. Is that the way it happens? I don't know, but it makes some sense knowing what I've observed with a pressure cooker.

[John Hart]

That makes sense Raymond. The Exploding Cell Theory. Could be a Nobel Prize in there some where!!!;)

[Raymond Overman]

That makes sense Raymond. The Exploding Cell Theory. Could be a Nobel Prize in there some where!!!;)

I like to think of it as The Magic Cell Theory. Where did the water go? Does it matter as long as it's gone without cracks?

Nobel? Heck, I'd settle for lunch and a handshake but the million bucks would be nice.

[Jim King]

Yes, for a rough turned bowl we turn down to 3/4 to one inch and boil a "minimum" of 4 hours and no problem if it continues for 8 to 10. Better than 90% success and the most of the 10% are repairable. The best thing is the drying speed. In 30 days you have a bone dry bowl.

As with Raymond I dont have any scientific reason for this. My guess is that the boiling removes the sap by exploding the cells and replaces it with water which dries much faster than resins. We boill 3" thick gunstocks 3 days and nights before air drying to them 20% before kiln drying. No cracking there either.

To say I beleive in boiling is an underststement. We are currently investing about $6,000 for the machine to vacumn pack all our blanks so the do not dry out or mold. It arrived last night. Now our next shipment will be fresh wood packed the same way as bacon or smoked fish. Every blank will have boiling instructions included. As soon as we figure out how to run this thing I will post some photos.

Before we were boiling our rough turnings we could not ship by air freight the finished peices to the States. The dryness of the airplane cracked many. Now with boiling and drying no problem. As we make a living doing this I can assure you that you will never see a 6 inch thick beautiful bowl blank sitting in our shop drying and destroying itself.

[Jim King]

As a final note to my message yesterday, here is the vacumn pack machine and one of the first trial peices. We can now pack and ship our blanks wet without fear of drying and cracking or molding. Vacumn pack material is nylon and very strong.

[Jim Becker]

Looks like "shake" to me...'probably already cracked before you turned it.

[Paul Downes]

Just thought I'd throw in another idea. I have been told that anchorseal is the way to go to prevent end checking. Also was told that latex paint wouldn't work because it doesn't retard moisture loss enough. (a lot of guys still use paint) I wonder if one painted with paint or some ratio of thinned paint that would allow the blanks to dry at a somewhat controled rate? It might be easier to paint rather than worry about which bag to use.