THE WOODRAT IS BACK!
Articles Forums Gallery Marketplace Videos

WoodCentral Forums

Est. 1998 — 27 years of woodworking knowledge

Need a tree taken down or milled?

Flattening a burl slice question

Posts

Flattening a burl slice question

#1

Flattening a burl slice question

Barry Irby

Years ago my son brought a burl back from Florida. and had it sliced into sheets and set them aside. We have three that are about 30" in diameter and maybe 1" thick. They vaguely resemble potato chips. About 2" out of plane. He would like to flatten them.

How would you soften them enough to press them flat? I am thinking steam. Some kind of steamer box. Then some kind of press to flatten them. Maybe park the truck on them for a while. I don't know what wood they are but it is something I have never seen and had and tough.

Any suggestions?

Re: Flattening a burl slice question

#2

Re: Flattening a burl slice question

Ralph Lipeles

I've steamed small strips when I was building a strip canoe. Your project is a little bit bigger. I would build a steamer box about 1" higher then the slabs and a little bit over 30" by 30" Next, the steam inlets and exhaust ports. Drill 2 holes on one end 7 1/2" from each side. The diameter of the holes should be the size of the pvc that you will be using for the steam inlet. Now drill 2 holes on the other end of the steam box for the steam outlet. These holes can be a little bit smaller diameter because some of the steam will have condensed. I guess that it will take quite a while to soften such large slabs so I wiould also drill some small drain holes on the bottom so that the condensed water has a place to go. Now make up some pvc to connect from the steam source to the inlet holes of the steam box. Now you should be all set to go. Make sure the the steam source puts out a lot of steam so the the entire steam box has a good steam flow. If you wanted to get really scientific you could drill some holes in the steam box for a temperature probe. The probe would tell you if you were getting even steam flow. When using the steam bow, rest the slab on small 1/2" thick pieces of something that will raise the slab to the middle of the box so that steam will go above and below the slab.

Re: Flattening a burl slice question

#3

Any Idea how long to steam?

Barry Irby

You and I are thinking along the same channels, but now I need to know an estimate of the time.

Re: Flattening a burl slice question

#4

Re: Flattening a burl slice question

John K Jordan

Boiling softens the lignin. Haven't heard of anyone with experience in bending after boiling. You could try an experiment.

Re: Flattening a burl slice question

#5

JL

Re: Any Idea how long to steam?

JL

No idea - typically for most steam bending it is a hour per inch of thickness.

Then you add a fudge factor for other dimensions. As an example, when I bend a hoop for a chair - I rough the hoop to about 1". When I do bend a crest - they are typically about 3/4" or so at the bottom by 3-4" tall (by however wide) - typically steam those for a hour When I have bent black walnut rails - 2" tall x 1" thick x 3' long - those were steamed for about 1.4-1.5 hours.

You are talking something 30" wide x 30" - so the steam only diffuses in and softens from the top and bottom - not really from the sides. You would then have to clamp them until dry. So if you were using 3/4" plywood with perforations - that would take forever.

Would you cut them into smaller, more manageable pieces? Say 4" strips or so? You could do a few trials and steam a lot easier.

Re: Flattening a burl slice question

#6

Ellis Walentine

What's next?

Ellis Walentine

Whatever shape these slabs have arrived at is the natural shape they will always want to take if left to their own devices. So, this begs the question of what your son intends to do with them once you've flattened them. Whatever that might be, my advice is to plan to provide a structure that will secure them, that is engineered to adequately resist whatever cupping/twisting forces the wood may exert.

Ellis

Re: Flattening a burl slice question

#7

Re: What's next?

Barry Irby

You are right. He wants to make a coffee table out of one of them. This was not well thought out. Had no plan at all when we had the burl sliced. Should have left then all in one thick slab and then flattened it. Probably could have gotten one table out of it. Now we may not get any.

One of my "rules" is Don't leave until you have someplace to go. I think we broke that rule.

👍 This page answered my questions

Your vote helps other woodworkers quickly find the answers and techniques that actually work in the shop.