cupped hardwood

[sgimbel]

I have some 8" wide 1/4" oak that is cupping. Opinions. If I just weight it down can I remove the cupping? If I wet it down and then heavy weight would that work? It's not cupped badly will just scrolling it relieve the pressure and cause it to uncup? Or did I just blow it! Scott in Round Rock

[campasano]

I was watching a woodworking show a while back, do not remember which one. They had a piece of hardwood that was cupped, they made a cut along the lenght on one side about half the thickness of the wood, applied glue into the cut and clamped it tight across the width of the board. After it dried the cupping was gone.

Mike

[wiwoodsguy]

At 1/4" it still can have some good pull in the wood so there is no telling if you can get it out stickering it down with weight or not. Usually bowing on a board 8" and up occurs on a board rift on both sides and face grain in the center. I usually just cut mine in half and make 4" material. Tis the season> You could try bending it back with stickers and weight. You could thickness sand it to 1/8" there would be less force from the wood and you could maybe stabalize it in a frame. Good luck, Mike

[tomsteve]

... or rip it and glue it up. i have wetted one side of a cupped piece of wood and weighted it down, with varying results. i think a lot has to do with what mike said about it being rift sawn. also the m.c could have changed

[sgimbel]

tomsteve, The m.c. could have changed? I haven't heard that term before. Please explain.

[unixpro]

Moisture Content.

[tomsteve]

unsealed wood is always absorbing and losing moisture. if the wood is sittin in the shop the m.c. can change with changes in the weather and shop temp.

[ncsealeveler]

Even if you wet,sticker and weight i believe it will cup again.Tony

[sawdustus]

Cupping is caused by the larger growth rings on one side of the board giving off a different amount of moisture during drying than the smaller ones on the other side. That is why furniture makers try not to use boards from near the center of the tree. You can put the cupped board, concave side down, on your lawn on a a warm sunny day. In a few hours it will have uncupped and then recupped in the other direction. Put it back in your shop and let it flatten. It may cup again but for a few days it will be usable for scrolling.

george

[wiwoodsguy]

I put a quick drawing together to explain. In case you were wondering if moisture had anything to do with the cupping. Absolutly! A Log when cut from a tree has about well it differs with species oak has 50- 60% moisture where as basswood in the log runs about 140%moisture content. Now you take cut it into lumber and sticker it weight it and let it air dry about 3 - 12 months. ussually about 12% is considered air dried. Then it can be used for outdoor project and in places where it won't dry much more than that. Now if you plan to use it indoors it should be kiln dried. In the kiln it is normally brought down to 6 - 7 % moisture then they accually put water in the kiln to bring it back to 8- 10 % to stabilize it. the reason to take it down to 6 -7 % is to make sure when you use the board for say a fireplace or something over or near the furnace duct blowing warm dry air over it it won't crack and check. Again back to the cupped board when a board cups it is always moisture related. The moisture in the air is enough over time to cup a board. Now if you are talking about a 1/4" or less in thickness it will be more apt to cup because the moisture comes and goes in the board as it does not have mass. I have always said that wood under 1/4" should be treated as a veneer and the best way to take care of veneer is to lay it flat and try to keep moisture away from it. to the picture near the edge of most boards 8" and up you will find Quarter which is when your grain runs 90 degrees with the face of the board or rift which is like 60 -85 degrees with the face. in the middle is flat sawn. if you look at the end of the board you can tell which way it will cup. In the case of the drawing it will cup up to the as the center dries uneven with the outside. If you straighten the cup it does not mean it won't cup again. However if you use it after you straighten it and then finish it with whatever means it will then be harder for moisture to come and go and after you finish it will be less likly to cup. But my point is it is all about moisture in wood. The best thing to do with thin stock is to keep it layed flat and away from moisture. Mike