Platter drying experiment 1 (Very LONG, sorry)

Re: Pic #2

Gary Evans, Tallassee, TN

>In this picture you should be able to see the side of the platter, along with the plastic stuff that is cushioning the edge and the bottom.

Gary

Re: Platter drying experiment 1 (Very LONG, sorry)

jeff jilg

>Gary - I never tried that, it looks like an interesting experiment. Longterm I would be concerned that the finished piece might try to revert to its internally desired warped shape. Wouldn't the internal stresses react over a few seasons to warp the piece after it contact normal humidity? So you might end up with a round shape now, but then in 2 or 3 seasons it could warp.

Re: Platter drying experiment 1 (Very LONG, sorry)

JHS

>That's what happened to me with a large walnut platter

Re: Platter drying experiment 1 (Very LONG, sorry)

Hawaii Turner

>Gary,

I wonder that if it is restrained from moving by your clamping, will it split instead?

Aloha, Doug

Re: Platter drying experiment 1 (Very LONG, sorry)

Mike Schwing from Md.

>Applause for your experimentation! I'll be very interested to see how this goes. Here's what I suspect: You will succeed in drying this with minimal distortion. BUT, a little seasonal moisture will cause it to begin to warp as it had intended to in the first place, and it might even crack. You're going to have a whole lot of tension captured in that platter when it dries, and I wouldn't be suprised if even something as simple as wetting it down to raise the grain causes a visible distortion.

Please keep us posted.

Re: Platter drying experiment 1 (Very LONG, sorry)

Ruth Niles

>Mike,

Would it help eliminate possible cracking if Gary coated the turning with an oil?

Someone (might have been Russ) told me when you final-turn green wood, it helps the wood adjust to the moisture loss. I have a really hard time rough turning only because I want it NOW, and non of my bowls have cracked after drying and I'm attributing it to the oil. What do you thing?

Re: Platter drying experiment 1 (Very LONG, sorry)

Gary Evans, Tallassee, TN

>Good point, Jeff,

This experiment is along the same lines as applying weight to the top of a stack of lumber to keep the upper layers from warping.

I'm hoping that the relative thinness of the platter will help the stresses to even out over time. I have nothing but time for this. If I have to keep it pinned down for a couple of seasons, I can do it.

Thanks,

Gary

Re: Platter drying experiment 1 (Very LONG, sorry)

Gary Evans, Tallassee, TN

>You may be correct, Doug,

I am hoping that the thinness of the platter will help to cut down the magnitude of the drying stresses that develop. This one is getting the slow-hand approach. That should allow the wood to gain strength faster than the stresses build.

Thanks,

Gary

Re: Platter drying experiment 1 (Very LONG, sorry)

Gary Evans, Tallassee, TN

>Thanks, Mike,

I'm going to pull it out of the clamp this weekend and drill those vent holes that I talked about. I expect it will be a number of months before it comes back out. I'll let you know in a year or so how it's doing.

Gary

Re: Platter drying experiment 1 (Very LONG, sorry)

John K Jordan

>Good experiment. I have wondered about trying to keep things round by constraining green bowls while drying, perhaps by forcing them into a cylinder or cone, perhaps even steaming first. Green wood is relatively soft and pliable, just like steamed wood. Heat and steam a thin piece of wood and bend it and when it dries it stays bent.

Wood seems to get so much harder when "cured" I wonder if there is some chemical change going on such that later seasonal movement will not completely undo. If the wood is thin enough, it may even dry and harden without cracking.

JKJ in East TN

Re: Platter drying experiment 1 (Very LONG, sorry)

Mike Schwing from Md.

>Hi Ruth,

I don't do much green-to-finish turning these days, but when I did I had very good success liberally coating the turning with oil (I used walnut oil but only because I had it on hand), and then putting the turning in paper grocery bags for a couple of weeks. In fact, I recall even having success at keeping pith from cracking with this method. I don't really enjoy that kind of turning so I don't do it much anymore but if I did I'd employ that method again.

I don't have any science to back it up, but as to helping with this particular experiment, my hunch is it won't make much of a difference.

Re: Platter drying experiment 1 (Very LONG, sorry)

Gary Evans, Tallassee, TN

>Hi Ruth,

This one has two coats of Velvit Oil, and I'll probably put another one on when I take it out this weekend. The oil should also help with my plan to slow down the drying rate. This helps to minimize the stresses that might otherwise create cracks.

The Relative Humidity, temperature and air movement determine the drying rate. The drying rate determines the stresses that build in the wood. If the stress exceeds the strength of the wood, then the wood starts to crack.

Fortunately, wood gets stronger as it gets drier, so the trick is to maintain a drying rate where the strength curve is slightly ahead of the stress curve. Since I haven't checked the moisture content of this wood, I'm sort of flying blind on this one (that's where the art comes in,) but the high RH in my shop is my best friend in this situation. It's hell on tools, but great for drying wood slowly.

Otherwise, I would have to devise a way to create a high RH until the wood gets down to 25% MC or so, at which point the strength is close to maximum.

Gary

Re: Platter drying experiment 1 (Very LONG, sorry)

Gary Evans, Tallassee, TN

>John,

I'm expecting to see the platter act like the steamed wood you mention. I expect, over time, that it will take a "set" that will keep it relatively flat from that point on.

If you couldn't force wood into the shape you want, then green-wood bending, as well as restraining stickered wood with weights, would not work very well.

By the way, I appreciate you allowing me the conceit of calling this an experiment. Since I don't have a control involved, and my sample size is quite limited, it isn't very scientific. With your background, I thought you might bring that up. 8^]

Gary

Re: Platter drying experiment 1 (Very LONG, sorry)

Carol Reed - Strawberry, AZ

>A suggestion, if I may, Gary.

Unless you have a plethora of clamps and don't need these for the several months you want to run this experiement, you might drill bolt holes through your plywood, install long bolts, nuts and washers. Easy to tweak the plywood for even space all the way around and frees up your clamps.

Just a thought.

Re: Restraint while drying

Russ Fairfield

>Yes, restraint while drying will help. It works for drying lumber and veneer, and it will work for your platter or bowl. Several things that might help, and some suggestions for further experimentation.

Be careful to not use too much weight. This is a case where, if a little is good, more is not better.

Like any other piece of wood that is being dried, it is important that there be no moisture gradient across the piece of wood across the piece while it is drying. In this case that means that the exposed rim doesn't dry faster than the rest of the piece. Being thin will help, but you may need more than that. You can do this by keeping the rim moist with a spray bottle of water, and letting it dry after the rest of the piece has lost some water. I would suggest drilling holes in the board used for a weight. This will let out the moisture from under the weight.

Several layers of newspaper between the wood and the weight will be helpful for keeping the moisture equal. Change the newspaper when it gets damp.

Keeping the rim damp also helps keep a bowl rim from cracking while it is drying. Drying a bowl upside down with the rim on a damp towel will keep the rim from drying faster than the rest of the wood. Keep the towel damp until the rest of the bowl has started to dry.

Bowls respond very well to band clamps around them, particularly if they are being dried in an enclosure with a controlled environment such as a kiln or a drying room.

We can also prevent some of the cracking that always happens across the foot of a rough turned bowl by mounting the green wood on a face-plate that will not be removed until after the bowl has been dried, turned the 2nd time, and finished. A hose-clamp can be used around a chucking spigot to do the same thing.

Re: Platter drying experiment 1 (Very LONG, sorry) *LINK*

John K Jordan

>>Since I don't have a control involved, and my

>sample size is quite limited, it isn't very

>scientific. With your background, I thought you

>might bring that up. 8^]

Well, I imagined there were plenty of control samples around with a variety of woods and shapes - nearly everything green I turn warps and/or goes out of round regardless of whether it is flat or deep. Even Tuesday evening, you could see the platter was warped and I doubt it would ever flatten out by iteslf! If you are successful in keeping it flat, I think it is an excellent experiment even without controls.

I've also read of people microwaving bowls, and while hot and steamy, warp them significantly for an extreme effect. Your "unwarping" is similar. Of course it would be far simpler to make something "precisely" unround and unflat rather than precisely round and flat! For your platter, I suspect you could easily control the flatness but not any oval shape.

Another data point - read about the guys who turn the amazing wooden hats - they build bending jigs made of sticks, rubber bands, springs, etc to shape the hat exactly as desired. Once shaped, it seems to stay. Although these hats are far more complex than a platter, seems this is technique, not experiment.

JKJ in East TN


http://www.woodhat.com/workshops.asp

newspaper

John K Jordan

>>Several layers of newspaper between the wood

>and the weight will be helpful...

I've had the ink from certain newspapers come off on my hands. Seems like those papers might stain wood, especially damp wood.

For those who don't know, in many places you can get free rolls of unprinted newspaper for the asking. I get end rolls from the local paper and use them for a variety of purposes. No ink to deal with and you can wrap things with very long pieces if necessary. Ocassionally they even have end rolls of white bond paper.

JKJ in East TN

Re: Platter drying experiment 1 (Very LONG, sorry)

Barry N. Turner

>Since you are restraining the blank from movement while it dries, wouldn't it be more prone to cracking, since it won't be able to move and by so-soing relieve it's internal stresses?

Re: Platter drying experiment 1 (Very LONG, sorry)

Gary Evans, Tallassee, TN

>Hi Carol,

The bolts were the original plan, but I discovered that I didn't have any long enough. Saturday's evolution will include bolts.

Thanks,

Gary

Re: Platter drying experiment 1 (Very LONG, sorry)

Gary Evans, Tallassee, TN

>Hi Barry,

My thinking is that by controlling the drying rate, I will control those stresses below the level at which the wood will crack. Since the wood strengthens as it dries, the drying rate can increase as the platter gets drier.

I like Russ's suggestion about keeping the rim moist. I am going to try to incorporate that in my plan.

Thanks,

Gary

Re: Platter drying experiment 1 (Very LONG, sorry)

Barry Irby

>It seems to me that the clamps or bolts will loosen over time as the bowl drys and shrinks. Perhaps you are monitoring this closely and manually keeping the bolts tight? Why not use some springs? You can get an assortment of springs and find ones that apply enough pressure. Also, not much chance of over tightening them.

Re: Platter drying experiment 1 (Very LONG, sorry)

Gary Evans, Tallassee, TN

>Hi Barry,

If this pans out, I may rig up a press with springs for a future green platter experiment. With this one, I wanted to be able to control the pressure as the platter dries. I was afraid to try to straighten it the whole 1/4" at one go. After I drill the vent holes this weekend, and install the bolts, I'll try to take it the rest of the way to flat.

By the way, how did you come out with your solar lumber drier?

Gary