White spots on elm slab and potential cupping?


Arlowtis
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As I get this slab set up to air dry (elevated, stickering, weighting) I have noticed a couple things that raise concern. 

Here's a new album highlighting these: https://ibb.co/album/jpDBbF

First I am wondering if anyone knows what the white spots are in the wood? Will these potentially go away with sanding?

Also, it appears I may have some cupping on the end with the large crack. After laying a straight board across I've noticed a gap beneath it in the center of the wood. Is this considered cupping or is it more likely due to the crack? Any options on whether further lifting can be prevented OR if the addition of the iron legs later on bwill help pull the edges back down? 

I know ripping the pith out is an option.

Seriously hoping I didn't buy a completely bunk slab. 

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You did not buy a bunk slab, you bought a slab with the pith through the middle, you have only one solution, cut the pith out. Any other attempt to prevent cupping will not work.

As for the white spots it’s hard to tell but I’m betting the inside of that slab is a lot wetter than you realize, definitely wetter than your outside readings. 
 

One positive, once you cut out the pith you’ll have two nice quarter sawn pieces.

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That pith has gotta go. It's just gonna keep moving & cracking. Cut it out & glue it back together. that looks like a pretty straight grained slab, & the glue line will be barely noticeable, if at all. I know you're stuck on the idea of having this huge single piece table top, but in reality you'll end up with something that's ugly & a constant maintenance headache with the continued cracking & cupping.

11 hours ago, Bmac said:

You did not buy a bunk slab, you bought a slab with the pith through the middle, you have only one solution, cut the pith out. Any other attempt to prevent cupping will not work.

This is exactly the truth.

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How did you measure the MC of the slab? A pin meter set on the surface is only measuring the surface moisture. You'd need to drive pins deep to get a good reading, also the reading should be towards the center of the slab not the ends. The ends are not sealed and that's why it's cracking at the ends, well in addition to the pith being included. If you have a pin less meter they tend to be able to measure deeper into the board. Also wasn't mentioned when the slab was cut. If it was this summer and it was outside until now it's not as dry as you think it is and I agree moisture could be causing those spots.

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6 hours ago, Chestnut said:

How did you measure the MC of the slab? A pin meter set on the surface is only measuring the surface moisture. You'd need to drive pins deep to get a good reading, also the reading should be towards the center of the slab not the ends. The ends are not sealed and that's why it's cracking at the ends, well in addition to the pith being included. If you have a pin less meter they tend to be able to measure deeper into the board. Also wasn't mentioned when the slab was cut. If it was this summer and it was outside until now it's not as dry as you think it is and I agree moisture could be causing those spots.

Using a pin meter as deep as it would go, which isn't significant on top. It's now reading at 18.5-19.3% in the center with the pins either pressed slightly in or nearly as deep as I can get them. My guess is it's crazy high in the center. Thanks for your input.

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7 hours ago, drzaius said:

That pith has gotta go. It's just gonna keep moving & cracking. Cut it out & glue it back together. that looks like a pretty straight grained slab, & the glue line will be barely noticeable, if at all. I know you're stuck on the idea of having this huge single piece table top, but in reality you'll end up with something that's ugly & a constant maintenance headache with the continued cracking & cupping.

This is exactly the truth.

I've come to realize that no amount of hoping is going to replace the knowledge that you and the others on this forum possess, and that this is a long-term project both in terms of allowing the wood to actually dry and repairs down the road. I do not have the tools to remove the pith, unfortunately. At least not cleanly and I really want to maintain as much width as I can. That being said, I understand I will be in for years of difficulty if I leave the pith intact. 

I have an opportunity to sell this to someone who can/wants to remove the pith, and is able to plane the remainder flat, and that's probably my best option. Wouldn't you say? 

I was really excited about the elm, but I'm going to have to choose something else from a more reputable source and start from square one. Which...is kind of where I am now. 

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If you "don't have tools" to remove the pith, what do you have? A handsaw and a handplane will take care of it, along with a large helping of patience...

I cut and squared a slightly thinner slab last year, to a level that light would not shine through the joint, with a hand plane. And the initial rips were made with a circular saw (didn't reach through), then completed with a hand saw.

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3 hours ago, wtnhighlander said:

If you "don't have tools" to remove the pith, what do you have? A handsaw and a handplane will take care of it, along with a large helping of patience...

I cut and squared a slightly thinner slab last year, to a level that light would not shine through the joint, with a hand plane. And the initial rips were made with a circular saw (didn't reach through), then completed with a hand saw.

Well that is amazingly helpful. Being relatively new to all of this, I assumed I'd need more! Thank you for your input. 

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