Antonia Edinger

[Antonia Edinger]

Hi, this is my second green turned bowl. I turned it. Dried it and it dried without cracks but warped in more of an oval shape.I turned it round again but I stuck in in a kiln to dry the shellac and it returned to an oval shape again. Do you think it was just not quite dry? My meter read 0% which I figured it was a bit off

 

[odie]

Antonia.......your link is not working for me, so can't see the photo.

The lowest meter reading I've ever had was 6% on a kiln dried board I once received......so, that 0% reading you got seems a bit suspicious.

I do not use a kiln, but rely on air-drying. I don't normally use a meter after a roughed bowl stabilizes, but when I do, it's around 12-14%.

ko

 

[Antonia Edinger]

That's what I thought too lol I'm not sure you can tell much from the photo but I'll try again

 

[odie]

That's what I thought too lol I'm not sure you can tell much from the photo but I'll try again

Right, seeing the bowl doesn't help answer your question......nice looking bowl though...... .....is it ash?

If you put your finished bowl in a kiln and it warped again, then my guess is it did reduce the moisture content.

What process did you use to determine the MC had stabilized prior to finish turning it?

 

[Antonia Edinger]

Thanks it's an oak bowl. I was weighing the bowls every few days and noting the change however I convinced myself that it felt so dry! So I put a meter on it and it read 0 so I thought maybe I left it in there too long...

 

[odie]

Thanks it's an oak bowl. I was weighing the bowls every few days and noting the change however I convinced myself that it felt so dry! So I put a meter on it and it read 0 so I thought maybe I left it in there too long...

You're not going to have much change in MC (moisture content) in a few days time, but many turners do trust their moisture meter to give an accurate measurement. For me, I go by monthly weights. I measure the weight, and when the roughed bowl does not vary in weight (more than a few grams) for 3-4 months, then it's stabilized. I can understand that you might feel hurried to get to your project faster......and, you might want to use some commercially kiln dried stock to put on the lathe immediately. Then you can use time as a determining element to make sure your air dried stock does stabilize to the local atmosphere before you finish turn it.

ko

 

[Owen Lowe]

When drying, oaks tend to shrink a lot compared to other US woods, I believe it’s on the order of 10-11% across the grain vs. with the grain. There is a US Forest Service wood data publication that gives shrinkages for commercial domestic hard and soft woods, though I don’t have the link at the moment.

I think your oval issue is probably from moisture loss. Like Odie, I only use the weighing method for determining when to re-turn a rough-out. The time it takes to stabilize is unique to your methods, atmospheric conditions, and karma. Frankly, I like an oval bowl as much as a round one -- I think it lends a visually organic feel to the bowl.

 

[Owen Lowe]

Here’s the link to the USFS document. Look on page 19 for the shrinkage chart though I find the whole publication kinda interesting.

https://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr117.pdf

 

[Antonia Edinger]

Here’s the link to the USFS document. Look on page 19 for the shrinkage chart though I find the whole publication kinda interesting.

https://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr117.pdf

Wow that's useful thanks. I figured I rushed it.

 

[Antonia Edinger]

You're not going to have much change in MC (moisture content) in a few days time, but many turners do trust their moisture meter to give an accurate measurement. For me, I go by monthly weights. I measure the weight, and when the roughed bowl does not vary in weight (more than a few grams) for 3-4 months, then it's stabilized. I can understand that you might feel hurried to get to your project faster......and, you might want to use some commercially kiln dried stock to put on the lathe immediately. Then you can use time as a determining element to make sure your air dried stock does stabilize to the local atmosphere before you finish turn it.

ko

Thanks I'll stick to monthly ones in the future. Although the oval shape is kinda neat..

 

[Bill Boehme]

If you turn wet wood to final form, it will warp and oak warps more than most. If you want to kiln dry wood, it needs to be done before the wood is turned to final size. If you put a finished bowl in a kiln it will warp a bit more ... even if it was already at EMC because EMC in the kiln isn't the same as room ambient EMC. Once wood has been thoroughly dried, especially if kiln dried, it isn't going to respond much to seasonal humidity changes.

Moisture meters aren't the best way to tell if a bowl has dried to EMC. Odie's method of weighing is the best way to tell if the wood is dry. A scale that reads grams is essential. You don't really need to know the moisture percentage... all that you really need to know is that the wood has reached equilibrium with its environment (EMC) which be when it is no longer losing weight. If you rough turn a bowl and either bag it or Anchorseal it, it should be adequately dry to finish in about three or four months.

If you want to include pictures in your post, you can either attach or embed them. You can embed a picture from a photo sharing site by clicking the picture icon above editor box. To upload a picture, click on the UPLOAD A FILE button below the text editor box. The photo gallery on this site is only for displaying completed work.

 

[Antonia Edinger]

If you turn wet wood to final form, it will warp and oak warps more than most. If you want to kiln dry wood, it needs to be done before the wood is turned to final size. If you put a finished bowl in a kiln it will warp a bit more ... even if it was already at EMC because EMC in the kiln isn't the same as room ambient EMC. Once wood has been thoroughly dried, especially if kiln dried, it isn't going to respond much to seasonal humidity changes.

Moisture meters aren't the best way to tell if a bowl has dried to EMC. Odie's method of weighing is the best way to tell if the wood is dry. A scale that reads grams is essential. You don't really need to know the moisture percentage... all that you really need to know is that the wood has reached equilibrium with its environment (EMC) which be when it is no longer losing weight. If you rough turn a bowl and either bag it or Anchorseal it, it should be adequately dry to finish in about three or four months.

If you want to include pictures in your post, you can either attach or embed them. You can embed a picture from a photo sharing site by clicking the picture icon above editor box. To upload a picture, click on the UPLOAD A FILE button below the text editor box. The photo gallery on this site is only for displaying completed work.

Great information thanks I will definitely keep that in mind for my bowls Thank you as well for the photo information. I thought loading the picture that way seemed strange.

 

[hockenbery]

That's what I thought too lol I'm not sure you can tell much from the photo but I'll try again

Nice bowl for your second try.

You centered the grain well and those bowls always warp oval and quite symmetrically when the grain is lined up well.
If you wait until the rough out is dry to 8-10%MC the returned bowl will hold its shape,in most houses.

 

[Mike Johnson]

If you rough turn a number of bowls you won't be in a hurry in getting the only one done.
Having a handful of rough turned bowls you can monitor the weights and moisture content of
each one and work with the ones that are ready.

 

[Antonia Edinger]

Nice bowl for your second try.

You centered the grain well and those bowls always warp oval and quite symmetrically when the grain is lined up well.
If you wait until the rough out is dry to 8-10%MC the returned bowl will hold its shape,in most houses.

Ah ok thanks. I probably wouldn't be able to replicate this but it does seem pretty symmetrical so I'll just tell everyone that's how I meant it to be

 

[john lucas]

Some woods have lots of internal stress and will warp after you remove a lot of wood even if they are dry. Limb stock is the worst about this and Oak is fairly bad so if you combine the two you get a pretty good chance at some wood movement when your turning. That's the reason we tell you when your hollowing a bowl and you thin out the rim, don't go back. As you get down the bowl the rim will move enough that it isn't round anymore, and that's on a dry piece.
I just turned 2 Beads of Courage boxes. Both out of very old and certainly dry wood. I had an emergency and couldn't get back to them for 12 days where they sat on my workbench. When I got back the lids no longer fit in every position. They didn't move much just .035". The lid moved less but when you added those two together the lid would fit loosely in 2 positions and was too snug for the fit these boxes are supposed to have in 2 other positions. I took away more wood last night.

 

[Antonia Edinger]

Ahhh ok makes sense.