I’ve got some 5/8″ hemlock that is slightly cupped. Normally I would hand plane these boards, but I need them at a thickness of 3/4″ to 5/8″ and don’t want to plane anymore.
I’ve read about wetting a towel and placing it on the convex side and using an iron to flatten the board.
Is this a temporary solution? Do the boards cup again once they dry?
Any suggestions?
Replies
Dampening one face of the wood is only a very temporary fix, the cup will return within minutes to a few hours. If the wood loses even more moisture, if it is indoors in the winter for instance, it will cup even more. If the wood is still losing moisture because it isn't fully dry it will also cup more.
John White, Shop Manager, Fine Woodworking Magazine
This is hemlock that was purchased right after being cut from the log. It has been drying, with stickers, in a breezy (old) barn for several months. Would it have helped (to prevent cupping) to weigh the pile down with cinder blocks while drying?
Strapping the pile, with ratcheting nylon cargo straps, might have reduced the cupping partially, if you kept retightening the straps as the wood shrank, but the forces generated by shrinking and expanding wood are quite large, the weight supplied by a few cement blocks would make no difference.
John W.
You could try ripping them in half and gluing them back together.
But as John said. If they are still losing moisture, then they may still continue to cup.
J.P.
There was a time when we used to frame houses with hemlock. This is a very difficult species. It twists and warps something awful. We used it green and tried to get it secured as fast as possible. Smaller members like 2x4s, would still warp and need replacement or fixing. I don't think I'd want to build any cabinetry or furniture out of it. I have a clear memory of the soaking wet saw dust, the sweet smell and standing on a two story wall plate, hand over hand, hauling up 2x10x16 rafters that weighed almost as much as I did. The only lumber I've used that was more cantankerous was tamarack, (larch).
I used some hemlock a few years ago, mostly for the rough beams. This was a loft type apartment, over a garage, with limited windows. The owner wanted a rough grid to separate a sleeping area but still let in light. Much of the lumber has checked but it didn't warp into a twisted mess, probably due to the construction of many half laps or luck.
Thanks for your info. Basically I bought the Hemlock because it was cheap and easy to get from a local Amish man. I paid $3.80 for a 11"w X 8' long board. I bought about a dozen boards. I was planning on using it for benches and a settle (bench with a back), rough type furniture and some smaller 18th century repro pipe boxes, etc.
I was very carefull to stack and sticker the lumber in a breezy barn, protected from rain. The stuff did cup and it sure did bend too. I'll probably rip it into smaller pieces and use it for small stuff but even working the wood over the weekend with my hand planes, I noticed that their is no rhymn or reason to the direction of the grain. The Amish guy cut the logs to get the most out of the log. Not the best grain pattern!
This has really been a good learning experience. You get what you pay for.
Cheap and easy in the world of woodworking ultimately leads to time-consuming and expensive.Please read this disclaimer which is an integral part of my post: Do not copy, print, or use my posts without my express written consent. My posts are not based on fact. My posts are merely my written opinions, fiction, or satire none of which are based on fact unless I expressly state in writing that a statement is a fact by use of the word "fact." No one was intended to be harmed in the making of this post.
"I've read about wetting a towel and placing it on the convex side and using an iron to flatten the board. " Oh, that's funny. I think the procedure got a little mixed up in the retelling, somewhere along the line.
You need dampness on the concave side, as that is the side that has lost moisture disproportionately, and cupped. You need a heat source on the convex side, but if you use an iron, you're going to get awfully, awfully tired! It takes quite awhile (say an hour, maybe two?) for the concave side to absorb enough moisture as the convex side dries a little more, to loosen up and flatten.
The orignal method was grass and sunshine, but not too hot or direct. A towel and lamp can be substituted. I have used this method, but mostly on old tables, such as a side or end-table, that had become mishappened. The thing is, you must get a finish of some sort on the wood as soon as you can to have any hope of it staying flat.
The thing about new boards (never milled and finished) is that you're fighting what's set in the wood. With an old piece of furniture, you can figure that at some point in its life, it actually was flat. If you want to try it, one more tip: After the first treatment, set the board where it gets circulation all around and let the obvious moisture on the "grass side" dry. If it re-cups, go through the procedure again, but let the board cup ever so slightly in the other direction, remove and let surface dry again. You can try that maybe twice. If it quickly re-cups, you're sunk. If it seems to stay flat, get some shellac on it really quick, let it set a day or two (always with complete air circulation) and see if it stays there.
forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)
Edited 6/26/2007 12:00 pm by forestgirl
The towel and iron are used on the same side (concave side) not opposite sides.
Here's David Marks on the matter:
http://www.diynetwork.com/diy/ww_other/article/0,2049,DIY_14443_2559170,00.html
(scroll down)
Or you can read Tage Frid if you have that in your library.
Both recommend the same technique as do others.
You appear to have it slightly wrong (the wet towel and iron part, that is)
You might like this source, one of my favorites:
http://aic.stanford.edu/sg/wag/1995/WAG_95_howlett.pdf
But you can try to dry the convex side by laying the board out in the sun with the convex side up. The concave side of the board is the dryest. That's why the towel and iron trick on the concave side works - by steaming only one side of the board. (the dry side).
This is easier than trying to get the convex side as dry as the concave side (or equalizing them with grass on one side and sunshine on the other). The iron and towel work remarkably quickly. One needs to be ready to put the board into the project, or cut any required joinery and bang the thing together in the same day, if not within a few hours.
Please read this disclaimer which is an integral part of my post: Do not copy, print, or use my posts without my express written consent. My posts are not based on fact. My posts are merely my written opinions, fiction, or satire none of which are based on fact unless I expressly state in writing that a statement is a fact by use of the word "fact." No one was intended to be harmed in the making of this post.
Edited 6/26/2007 3:17 pm by ThePosterFormerlyKnownAs
That's a new one for me, but glad to put it in my arsenal. As for the history of it all, I suspect there was grass and sunshine in use long before towels and irons were thought of. I like that twist on it though, since sunshine's in pretty short supply here in the Great Northwest.
forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)
Edited 6/26/2007 11:39 pm by forestgirl
You're just steaming one side of the board with the wet towel and iron - the "tight" side, if you will....
It works, it can be a lifesaver if you have a beautiful board that cannot be replaced.
Please read this disclaimer which is an integral part of my post: Do not copy, print, or use my posts without my express written consent. My posts are not based on fact. My posts are merely my written opinions, fiction, or satire none of which are based on fact unless I expressly state in writing that a statement is a fact by use of the word "fact." No one was intended to be harmed in the making of this post.
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