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Warping wood question

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Anonymous

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Ive had a board of mahogany up in the loft for what must be over 10 years now & so I guess its well seasoned.

Yesterday I cut off a piece about 8" wide & thicknessed it down to approx 10mm thick, it came out perfectly flat from the thicknesser & by the time I had done that & some other jobs it was the end of the day so I just left the woods on my bench.

When I came in the next morning I noticed the wood was no longer flat, it had curved slightly over the 8" width & so I thought if that was a panel for a door or something it would be pretty useless now.

What have I done wrong? should I have left the pieces clamped overnight or with some weights on them to prevent bowing? or am I doing it all wrong? should the 8" wide piece have been made out of strips of say 2" wide making sure the growth rings are alternating as Norm always seems to do & then biscuit them together?

Any advice would be handy to me right now as up until now ive been making up little jigs & things with just soft wood from "Wicks" but it seems now im working with "Real" wood im experiencing these sort of problems.

Thanks guys,
Nick :?
 
A

Anonymous

Guest
Normfan,

Warping like this usually happens because of extreme change of humidity. ie the loft is dry, the workshop damp or vice versa.

I would imagine you would have needed to have left the full board out of the loft for some time before converting it.

I will prepare to be shot down in flames here!!
 
A

Anonymous

Guest
A Couple of Mistakes Possibly made there Norm Fan

Firstly when you put a piece of seasoned timber through the Planer Thicknesser you should remember to reverse the timber each cut, trying to remove the same amount off of each side, if you work just one side the side the planed side will react by either retaining or absorbing moisture causing warping.

Secondly you shouldn’t have left the piece flat on the bench over night, this means that only one side has acclimatised to the workshop humidity and again causing a warp.

Bad luck on both accounts. It will be difficult now to re flatten the timber without re working at the thicknesser.

Best of luck
 
A

Anonymous

Guest
Stevezm,

Is it not equally the case though, that if the full board you start with is the same humidity as the enviroment the finished article is going to go into, then the planed piece will be stable? If the difference between the loft and the workshop is big enough then perhaps you havn't given the wood enough time to aclimatise before planing?

I know from the past, extremes in humidity can have a drastic effect on the way wood moves. Try putting the planed piece back in the loft and see what happens? I have never had success with wetting and cramping. It always goes back to where it wants depending on the humidity.

Hell, this is one of the reasons why I could be a bit reluctant to go into making furniture!!

Regards
 

johnelliott

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Various points come to mind, and might be worth mentioning.

First of all, humidity. Have you measured it? In the workshop and in the attic. If not, go to your local garden centre and for about a tenner buy a hygrometer, which will indicate the relative humidity. I won't quote numbers as the hygrometers vary a good deal, but measure it in your living room first and then try the workshop. If there is a difference of more than say 10% then you will be fighting a losing battle, and anything made of solid wood in the workshop will tend to bend when it is brought indoors. Even paper will give you an idea of whether or not there is a problem. Take a piece of paper from your house and leave it overnight in the workshop. Is it still as crisp and crinkly? If not, then there's a humidity problem in your workshop. Various solution possible- dehumidifier, sealing floor, walls and ceiling, a little dry heat, all will help.

Also, bear in mind that as wood grows it develops internals stresses and tensions, which, when some of the wood is removed, will release, causing bending. If possible plane and thickness your wood to NEAR the required dimension, then leave it for a while until it has warped if it is going to, then plane it again and thickness to size

8 inches wide and 10 mm thick, I would expect most woods to bend a bit, especially if, as Steve says, it is all removed from one side

One last point, seasoned is not the same as kiln-dried

John
 
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Anonymous

Guest
John,

Just to pick up on the Hygrometer and dehumidifier.

I bought one some time ago. It's amazing how the humidity levels go up and down. I wouldnt be without it now.

I've used dehumidifiers in a single garage size workshop. After giving them about 2 or 3 weeks to get going , again, amazing the difference. You can feel it on your face as you walk in. Much dryer and better for the tools as well!

Regards
 
A

Anonymous

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Matstro

Yes the change in room humidity will have a great effect on the timber and you should allow the timber to acclimatize. If loft to workshop is similar then a week should be enough.

But even so you must never leave it on a closed surface to acclimatize, i.e. a bench; this will mean the one side reacts quicker and hey presto banana wood.

I find it’s almost impossible to rectify the matter after the event without some reworking.

Putting it back in the loft, probably, won’t work as the one side of the timber has now changed considerably in structure. If you work out whether the side you have cut has cupped or bowed then you will need to treat the other side accordingly and then clamp and cross your fingers.
 
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Anonymous

Guest
Thanks a lot to everyone who replied, I appreciate the help :)

I will try out a few things that you have all suggested but in the meantime I have another question for you all (uh oh here he goes again) :roll:

Im planning on making a little bedside cabinet for my mum out of cherry maybe, if I make up the cabinet & then use an oil like Teak oil to finish the item off will it still warp all over the place?

Why doesnt brushing oil into the wood cause it to warp like water/humidity does? in my finishings book it says oil is better than wax at heat & moisture resistance & I like it because it looks more natural than all of these varnishes & is dead easy to get on.

I like cherry but does anyone have any thoughts on what is the most stable & general all round best wood to make cabinets from?

Ok, I think thats 3 questions :shock:
Thx!
Nick
 
A

Anonymous

Guest
Normfan,

Just to go back to your woodwarping problem a minute. If you want to salvage the peice of warped wood, one way to flatten it that may work is to; Wet the (hollow)side quite liberally(that one side only) leave for a while, keep your eye on it then it may go flat or go the other way. When this happens brush on a coat of say 75% water to 25% PVA white woodwrking glue onto the opposite side (rounded side) When this glue "size" drys out it will tend to shrink that face of the wood which will in turn counteract the warp on the other side when the water drys out.

I hope you understood that! I didnt and I wrote it!!! Try out on a piece of scrap first. Bear in mind that if it works ,one side of the wood will have a glue film and won't take stain and alot of finishes, but at least it may well remain flat.

RE. Your other queries I'll let others have ago at them cos I've been described as a limelighthog!!!! I'll' chip in afterwards though!

Regards
 

johnelliott

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Books can and have been written about the subjects which you are enquiring about, and I don't think that there is very much we can tell you here. I will venture that no hardwood is conspicuously more prone to warping than any other, and that finishes will only slow down but not prevent wood reaching the same level of dryness as its surroundings.
Many techniques of cabinet making are designed to reduce the warping problem, frame and panel construction being an obvious example.

I think you would be well advised to get a couple of books from the library and have a good read.

John
 
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Anonymous

Guest
Thank Matstro for that tip, yes I think I understand what your saying, I will give it go on an off cut & see what happens.

Im off to my local library now to see what I can find on this, they always have really old books but then I guess this is an old subject that hasnt changed over the years so it should be fine.

Nick :wink:
 
A

Anonymous

Guest
Normfan,

Unfortunately, like all trades, its not till you've made things that then turn out to be a disaster that you learn whats right and whats not!

Books are a good idea cos they give you the basics on which to build the knowledge. Don't get too bogged down in them though, try to determine whats key stuff and whats not.

I guess all your questions could be answered here but then they would take the form of a book! Get some out, give them a read then post back with some specific points?

Good Luck
 
A

Anonymous

Guest
You see Norm Fan The question you ask has many answers and like Matstro says here can be better than any book sometimes but it's always worth cross referencing your answers.

Cherry, I love cherry, one of my favourite woods. Will it warp and why when you apply oil doesn't it warp. Here goes and this is only my basic lay understanding.

Warping takes effect when moisture is introduced in such amounts that the moisture content of the wood changes. If you buy kiln dried cherry when you get it in the workshop you must allow it to acclimatise and make sure the workshop humidity is similar to your mothers’ room.

Again plane/thickness both side of the timber to even out the shock factor and don’t store the wood at anytime flat on its face, this is the number one cause of cupping. The trick is, if you can look after the timber up to the point it becomes a cabinet then you have half the battle won.

Now if you oil the cabinet, so long as the timber isn’t going to be moved to a very different humidity the moisture content on back side won’t change much from that of the front and the cabinet itself supplies some stabilizing structure to the timbre also. Also the oiled side will continue to breathe moisture and will swell and shrink as normal.

Oil won’t affect the timber as far as warping is concerned, it is not as thin as water and doesn’t penetrate a fraction of the way water does. Think about it if you soak a board in oil it will warp eventually as it would if you soaked it in water. The air we breathe in is full of water not oil, therefore the timber is permanently soaked in water to some degree

Don’t glue in any panels, the cabinet frame will want to expand and contract over the years and you may want to apply the finish to these areas before assembly.

Crikey this is going on, sorry and there are loads of different angles that I could have gone off on and then it would have been a book. I will leave that to the rest of you.
 
A

Anonymous

Guest
Thanks for that info, its a real help..

Im sure I will get there in the end :)

Thx!
 
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