table top warping

[Mike McCann]

I am making a child table and chairs. the table top is 5 pieces of glued up cherry 24" accross by 36" long. Before I started to finish it the table top was perfectly flat. However i have finished the top now and when placing it on the leg structure there is a bow in the top about 1/4". What can I do to straighten this out. Right now I am trying by leaving the top on the legs and puting weight in the middle to see if it will push the bow down. I will then put some finish on the bottom. Will this work or is there something else I should try.

thanks
Mike

[Mike McCann]

Well

the weight on the boards does not seem to be working. Any suggestions.

[Stephen Edwards]

Can you take pics of the table, both of the top and the underside of the top, showing how the top is attached to the "frame" of the table?

There are several possible solutions to your problem. More info would likely get more responses.

[Howard Acheson]

Because you have only finished one side the top has developed an uneven moisture content on the two sides. The unfinished side has absorbed moisture from the humidity.This causes warping. You should always finish both sides within a short period of time. Also, never leave a panel lying directly on another surface. This will also cause uneven moisture on the two sides. Always raise the panel up at least an inch to allow air to freely flow to both sides.

If you have an area that is of lower relative humidity, you can try leaving it in that area and see if it flattens. In many areas, the indoor RH is less than the outdoor in winter.

You might also try drying out the unfinish surface. Once I rigged up a hair dryer to gently blow on the surface I wanted to dry. As I recall it removed most or all of the warp within a few hours or overnight. Keep a close eye on it and get to finishing when it is flat.

[Mike McCann]

The top is not secured yet to the table. I just finished the top and placed it on the of the legs to see how it looks. I just finished the top in shellac and it warped over night alon the grain lines. I will keep the wieght on it overnight to see if it flattens out when it does I will put some finish on it to seal it. I have checked my store bought dining and kitchen table and both do not have any finish on them.

[Mike Henderson]

One thing I've done in the past is to put the top in cauls to clamp it flat, then flood both sides with water. Allow to dry over night (or longer). Usually, the top will come out of cauls pretty flat.

Then put battens on the underside of the table to keep it flat. Two to three battens should do. They will be cross grain so don't glue them (except maybe in the middle), use screws and elongate the holes towards the ends of the battens to allow for wood movement.

Mike

[Stephen Edwards]

One thing I've done in the past is to put the top in cauls to clamp it flat, then flood both sides with water. Allow to dry over night (or longer). Usually, the top will come out of cauls pretty flat.

Then put battens on the underside of the table to keep it flat. Two to three battens should do. They will be cross grain so don't glue them (except maybe in the middle), use screws and elongate the holes towards the ends of the battens to allow for wood movement.

Mike

I've never tried the water bath method but I can vouch for the battens, just as you've described. It works.

[Mike McCann]

Thanks, Looks like with the wieght I have on it is slow straighrtening out. I will add the battens as you suggested to keep it flat.

[Tony Bilello]

I agree with Howard.
Normally, whatever you do to one side of a large piece of wood, you should do to the other. If the underside is left exposed to air, higher humidity will cause the bottom to swell and the top dont change. This swelling will result in the top cupping upward. Conversely, if you have a colder dryer period, the bottom will dry out and shrink and then the cupping will be downward.
The cupping can somewhat be avoided with stretchers.
If it doesnt take much effort to flatten it out with your finger putting pressure on it, then attaching the top to the apron probably will do the trick also.
It it were mine though, I would wait till it flattens out on its own with the weather, then go and finish the bottom side of the top.

[Mike McCann]

Thanks all for the advise. The top is now flat I have it clamped with cauls to keep it that way while I finish the bottom.