Thread: Bowing Timber after Biscuit Jointing

Welcome to the forum VV
The joys of working with real timber. If you have something that is flat, straight etc the best thing is to get finish on it as soon as you can. This often helps but not always. With some timbers you need to lay them alternatly (ununun) rings up and rings down so they cancel each other out rather than (uuuuuu). If I do a table top etc, I get it flat and smoth then clamp it to the bench untill I can get finish on it and clamp it to the table frame/legs. You might need to find a good book (often some of the old school books are cheap and full of info) to give you a bit of woodwork theory. Or just keep asking questions. The braces inderneath may help.

G'day VinVin,

forget the biscuits for a start, I'm guessing your talking about 140 x 19 Radiata Pine, just a simple straight butt glued joint is fine for this stuff and don't worry, it goes like Bananas anytime not just after you've messed with it.
Make a boat out of the one you've done and start again! Oppose the grain as the big Hama has said, Butt join, AV 1050 or something like that. Now heres the thing, if you have to go off and do other stuff for a bit and you have this kind of panel laying about in your shop, while you are away, gremlins will come in and try to make boats out of your panels for themselves, the way to stop this is to hide the panels under sarking, (they hate sarking)!
Truth is, although I like the story so far, temperature and relative humidity remain reasonably constant when wrapped up in sarking. (silver side out) a little weight on top while waiting will help also. You should think of timber as being a breathing animal, like a Lion waiting to pounce on it's prey, if you put a time lapse camera on a piece of timber over a period of time, you would be amazed at the amount of movement it has! How's that table coming Claw?

All the best ...Oddjob1

Vin , another hint .
Apply the finish to top and bottom , inside and out , all surfaces of the box.
That stops the moisture getting into the bare side of the wood and swelling it 'stretching it' as it were , while the coated side stays as it was .
The off-side only needs a sealer coat , no need to go the whole hog with it

Thanks for the advice...

Good thing i used cheap pine as my practice project.. the actual box has a hard wood frame and didnt bow at all.. so it looks like i might be starting again with the lid...

As for the Biscut Joints, hey, i had a new toy and needed to try it out

cant wait till i get my dovetail guides and saw, then i can really make a mess of things!

Silly question tho, and i havnt really had a good look at the grain on the pine, but is there an easy way to tell which side is which?

Oh yeah - and whats AV 1050?

Tag team happening here, AV 1050 is a wood glue made by Bostik. Or any pva, selleys etc. If you look at the grain on the end of your stick it will go either up or down. If you alternate them one will curve up and the other down rather than all up or all down. Like I said you need to do a tiny bit of theory, a good woodwork book for Christmas.

ahhhhh ok - i get the grain thing now- makes sence..

looks like tomorrow i'll be heading out to get more wood... I did realise just before tho, that where i had the box sitting with the lid on it, is under one of those clear sections in the roof, so, it might have been in direct sunlight at certain times during the day, which is likely to be an issue.

Thanks for your help people!

Well, looks like i cant even make a boat ... last night i clamped it all flat again, covered it up and left it. This morning, i unclamped it all and its back to flat again .. today i will brace it from underneath and sand and paint it..

Thanks for your advice guys ... i did learn alot.

Vin Vin I've left edge joined timber lying on a workbench in my workshop for a few days and it has bowed up like that. When I turn it over, or stand it on an edge for a few days, it flattens out. This is because when I leave it on the bench in a hot workshop the top loses moisture to the air and the bottom doesn't. Exposing both sides for a few days balances up the moisture content on both sides.

But the good advice has already been given. Get it ready and finish all over it as soon as possible to stop the uneven drying out in the first place.

I tried working woth biscuits to make some cupboard doors. Hopeless, same problems as you.

The biscuits have little or nothing to do with the bowing.

With the range of wood glues available today , one for every occasion , biscuits , and dowels for that matter , are not needed very often for end and side gluing of flat timber .

MDF is another matter due to the fact that it has no side or end grain strength

Can't see that the biscuits were the cause of the problem.

Use them all of the time as they are great for alignment and if used correctly do give some added strength to the join [ not wanting to cause the usual argument re biscuits v's whatever - just my opinion]. One of the main causes for bowing I have found is if your edges are not square.

yeah- i seee your point .. the panels i biscuit joined were for a lid on a toy box, which might have someone sitting on it or my child standing on it, and so i wanted additional support between the panels in lieu of edge glueing.