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How to UNwarp wood in cold weather

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Forum topic by Hillsboro posted 01-25-2013 11:22 PM 3973 views 0 times favorited 11 replies Add to Favorites Watch
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Hillsboro

43 posts in 1554 days


01-25-2013 11:22 PM

I am immensely frustrated. I know how UNwarp wood when the weather is warm and sunny. However, it is bloody cold in northern Virginia and I really do not want to wait for spring (unless that is the only solution).

I have a collection of 1/4, and 3/8 stock that I wish to use in a project. Unfortunately it is all cupped and/or warped.

Any suggestions on corrective methods would be appreciated.

Many thanks,

Phil Stevens


11 replies so far

View runswithscissors's profile

runswithscissors

951 posts in 681 days


#1 posted 01-26-2013 12:19 AM

I don’t have a solution for cupped stock, except maybe to joint it. But it sounds like you are at or near your final thickness. But for warped and even twisted boards, I like to use heat (not steam, just heat). My favorite tool for this is a propane powered infra red paint stripper I bought many years ago. But I have never seen another one like it, and was not able to find a website for the company. Next up is the heat gun, which will work well, except you have to be careful not to scorch the wood. Clamp one end of the board in a vise or to a table or vertical post. Play the heat over the wood where the warp is until it is very hot (but not scorching). That should be on the inside of the warp. Now start gradually bending the wood to straighten it. I do this by eye. You’ll need to over bend. Take away the heat, and hold the board in this position for a couple of minutes. This will let it cool enough that it will now hold the new shape. If it isn’t right yet, repeat. If you went to far, you’ll have to reheat it to unbend it.

If the wood has a twist, you can clamp a handle onto the end to give you leverage to correct that. Maybe somebody else can help with the cupping.

I have a feeling a lot of wood that LJs feel obliged to joint could be treated this way. And by the way, this works very well for bending plywood, especially thinner panels.

I needed a 10’ oak crown molding for my kitchen. The only one I could find in town was badly warped. Resembled a ski. I got it at a discount (nobody else wanted it), and using the above method, was able to straighten it out easily. Total time was maybe 10 minutes.

View MonteCristo's profile

MonteCristo

2097 posts in 845 days


#2 posted 01-26-2013 07:57 PM

The warping has relieved stress in the wood. By unwarping it, you may well be introducing stress back into the wood, even with the use of heat. Unless you counteract that, it will likely just go back to its initial state.

-- Dwight - "Free legal advice available - contact Dewey, Cheetam & Howe""

View Hillsboro's profile

Hillsboro

43 posts in 1554 days


#3 posted 01-27-2013 12:42 AM

Monte risotto:

Not informative or helpful. If that is all you can think of it would have been better to have said nothing

View TCCcabinetmaker's profile

TCCcabinetmaker

925 posts in 1011 days


#4 posted 01-27-2013 01:02 AM

actually monte cristo alot of cupping is due to uneven moisture content, from one side being allowed to dry more than another. Thus the wood shrinks on one side causing it to have a cup in the board.

Hillsboro it’s not necessarily so much the warmth of the day as it is the sun drying the wood, but at any case have you tried a heat lamp?

-- The mark of a good carpenter is not how few mistakes he makes, but rather how well he fixes them.

View joeyinsouthaustin's profile

joeyinsouthaustin

1256 posts in 729 days


#5 posted 01-27-2013 01:04 AM

I don’t know a lot about cold, being in texas, But often moisture is the key to warping, and winters get drier than usual. Is the problem related to the climate in your shop?? Also how would you un warp it in summer, that can’t be done in the winter? I ask that question honestly from the perspective of someone who suffered through a 75 degree day today. For me it is usually bringing the moisture back in line to relax the wood. So I am unsure what about your shop, or set up is allowing you to do it in the summer, but not the winter. While writing this scissors has offered an interesting solution, close to what I was thinking. I have done similar but with moisture, by ironing over top of a damp cotton rag on the cup side, and heat only on the crown side(with an industrial soldering iron I use for soldering door pans, not a home iron) With thin woods drying causes the shape changes In my experience. I am looking for an article I read. I kept a poster out of this at my office to remind me how things will change. Here is the next best thing I found. I will post the graphic next time I am at the office if you are interest pm me.

-- Who is John Galt?

View Jorge G.'s profile

Jorge G.

1526 posts in 1131 days


#6 posted 01-27-2013 01:08 AM

For the cupped board, you might try wetting the concave side. For the warped board I have no solution.

Maybe you should explain your project. It seems to me you are using very thin stock, maybe the wood would straighten up as you glue it.

-- To surrender a dream leaves life as it is — and not as it could be.

View MonteCristo's profile

MonteCristo

2097 posts in 845 days


#7 posted 01-27-2013 05:41 AM

Hillsboro

Look up the term “reaction wood”. You might learn something.

-- Dwight - "Free legal advice available - contact Dewey, Cheetam & Howe""

View joeyinsouthaustin's profile

joeyinsouthaustin

1256 posts in 729 days


#8 posted 01-27-2013 08:40 PM

Monte Great insight, however in my experience “reaction wood” (I have also call it wyld or live) generally changes shape after physically processes, like jointing, ripping, or shaping. Wood that has changed shape while sitting in the shop is usually due to losing or gaining moisture. IMO the situation hillsboro is describing is from sitting. Although as mentioned in my first post, I don’t have a real read on how tensed or compressed wood acts in extreme temp change.

If the cupping matches the picture according to grain, you may be able to fix it by bringing moisture back in line, or with one of the other options mentioned here.

I wood agree that if it has done it once it will want to go that way again.

-- Who is John Galt?

View TCCcabinetmaker's profile

TCCcabinetmaker

925 posts in 1011 days


#9 posted 01-27-2013 09:23 PM

not necessarily, but that’s why it’s important to stack wood properly when drying it or when storing it long term. And yes there are some slices of wood that will cup, however most wood unless specified is going to be straight sawn instead of quarter sawn, which is what your diagram is pretty much showing. Quarter sawing produces better looking wood, but produces less lumber, so lumber mills tend to not do it as often and charge more for quarter sawn.

-- The mark of a good carpenter is not how few mistakes he makes, but rather how well he fixes them.

View Hillsboro's profile

Hillsboro

43 posts in 1554 days


#10 posted 01-28-2013 04:08 AM

My thanks to all for the thoughts/comments. In answer to Joey’s question about fixing cupped lumber in warm weather: put it cupped side down on the grass early in the morning. The suns heat, and the wet grass will solve the problem. Just be sure to check the lumber often or you might end up with cupping in the opposite direction.

Clearly this is not an option in the winter. Virginia in the winter is cold and with the cold it is very dry in the house regardless of where one is. Therefore, despite how one stacks lumber problems arise.

I have discovered that careful use of a heat gun will solve the problem for my thin stock.

View joeyinsouthaustin's profile

joeyinsouthaustin

1256 posts in 729 days


#11 posted 01-28-2013 07:32 PM

I understand now why It would help if it was summertime, not to brag, ok maybe a little, I could have used that method yesterday, as it was 80 degrees, but is basically the same as the ironing over a damp rag. Glad you are able to un cup things.

-- Who is John Galt?

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