Can Horribly Warped Wood Slabs be Saved with Steam?

Today I have a fun special guest with me! Wink bought wood from me in the past, and in the last load of stuff that he purchased, there was a slab that was super twisted. When I moved the log that the slab came from to our new house, I never got it put away properly. I left it sitting on some dunnage out in the field, and it got super twisted. This is why I always tell people that it’s important to make sure slabs are flat when they are drying, because they will conform to the area they are drying in. 

So we are going to try steam bending this slab to take the twist out of it. You can see that one side is up by three inches, so a pretty intense twist. 

The slab that we are going to steam bend is 10’6’’ in length and 5’ in width. We need some buffer room, so the box will be 11’’ long and 6’ wide. 

We are going to make the steam box out of the temporary roof deck that I used on the sunroom addition over the winter. For the steam, I bought four of these self-contained steam generator units, plus I have one that I already owned. 

We have to figure out how tall to make the box to fit two slabs in it. To do that, we need to know how much twist there is for all of the dead space that the twist is going to occupy. After doing some measuring, we are going to make it 16 inches deep.

This is where the steaming is going to happen. We’ve got two slabs on here with some 2x in between so the steam can get to both of the slabs. Then the lid that we made goes on top and gets screwed on.

Next we get the steam generators plumbed into the box. We are putting them at the end of each side, towards the bottom. 

The generators have warmed up and are currently boiling, and you can see the steam rising out of one of the corners here. It’s currently 6PM, and we are going to run this overnight. Wink is going to keep an eye on the steam generators and refill them overnight as needed. Then we will do a real solid run tomorrow. 

Next morning, and the steam box is still cooking away. The steam generators get refilled at 9PM, 11PM, 3AM, and 6AM. Wink has been running these pretty much nonstop since then. I’ve burned through about 40 gallons of water already. We will run through all the water we have, and then unload the slabs into a form.

Here is the setup of the form for the slabs. We assume that the slabs are going to have some amount of springback, so I have tapered two of the bunks in the opposite direction of the twist. That way, when we clamp the slabs into this form, they will twist further in the opposite direction. While the slabs are in the form, we will put about 12,000 pounds of clamping force on top of it. Then when they come out of the forms, they should springback into flat. At least, that’s the plan.

So we will get these unloaded and into the forms as quickly as we can while they are still steamy.

We’ve loaded them into the forms and sandwiched them down with some workbenches and the forklift for weight. Now they are going to sit for a while.

It’s been two weeks, and I’m taking a peek at these slabs. They look surprisingly good. There’s no springback. There is a little bit of warp, but for the most part, they are conforming well to the form. They have surprisingly less moisture than I expected them to have, at about 14-16%. 

A month later now, and Wink is back to take a look at these with me. This slab looks so much better now. 

The original intention was for me to surface this for Wink to save him some time. The downside is that if you’re going to surface something that has these kinds of defects in them, and you’re planning on filling them with epoxy anyway, surfacing them now is going to cause all of this detail to get lost. The little fibers will get completely removed and blown out. Ideally, you fill these details with epoxy before doing any surfacing in order to preserve the crispness in the edges. So Wink is going to take it back like this, fill it, and do the flattening later on. 

Now it has been two months, and I’m getting moisture readings within 1% of each other depending on where I’m measuring in the slab. Now that I have tried out steam bending and know how it works, I can go through and flatten the rest of the slabs from that log, when I have the time.  

What a fun, weird experiment! So thank you, as always, for joining. I greatly appreciate it. If you have any questions or comments on steam flattening slabs, please feel free to leave me a comment. As always, I’d be happy to answer any questions you might have, and until next time happy woodworking!

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