Table Top Warping

[Phillbo87]

Hi i am quite new to woodworking and have recently started it up as a hobby with some general knowledge of it.
I have recently glued up a small table top approximately 350mm by 350mm it consists of 5 panels. Last week i got it all flat and square after it was glued together it was pretty much perfect so to my surprise i came back to it a week later and its warped slightly in the middle i am puzzled and pulling my hair out to why this has happened can anyone help please i know there is seasonal movement in hardwood but theres no way it should moved that much in a week. PS the wood is maple and walnut.

Many thanks

Paul

 

[Steve Maskery]

Hi Paul, welcome to the forum.
Wood can warp overnight, never mind after a week! How much is the cupping?

My guess is that it has dried out a bit since you planed it. As wood dries, it shrinks, and it shrinks more in some directions than others, which is what causes the cupping.

If the distortion is not much, you might be lucky and find that you can pull it flat when you attach it to the aprons. If you have lots of thickness to play with, you can flatten it again. Or you can just live with it as it is.

Several options, some more appealing than others, I know.

 

[Phil Pascoe]

Did you reverse the grain of the pieces? Heart side up, heart side down, heart side up ... ? That minimises cupping.

 

[RobinBHM]

It possibly absorbed more moisture one side, was it left on a bench with the upper side uncovered?

One solution it to suspend it above a heat source like an electric radiator. Keep the convex side to the heat. The heat will reduce the moisture content and flatten out the top. No guarantees it will end ip dead flat, all depends on grain pattern, timber etc.

If I make any worktops I now always keep them sandwiched between some ply or wrap fully in plastic or pallet wrap -just whilst not being worked, ie overnight.

 

[blackrodd]

Hello and welcome, To help minimise this cupping you have experienced,
When timber is stored outside, in a woodyard, or in unheated shed, it should be allowed to settle for a few days inside.
Best to let the timber settle indoors in a similar environment in which it will end up, before you machine it and joint.
Its also recommended that when facing and planing, as even amount as possible should be taken from each side.
And as Phil.p says set the grain out as opposites when you joint
And don't forget its very easy to over tighten the clamps and set a "bow", a prop from the ceiling will help.
As Steve says, fix the top and see what it looks like, it'll likely look very good, try it and see!
HTH Regards Rodders

 

[sitefive]

happened to me as well just now, was making a table for someone, but the delivery date changed by over a month,left it lying without attached to anything and it has warped now so badly that I have to make a new tabletop

 

[custard]

Did you reverse the grain of the pieces? Heart side up, heart side down, heart side up ... ? That minimises cupping.

There's some superficial logic to that, but the practical reality is that table tops almost always tend to cup upwards no matter what you do. Study enough antiques and you see that all heart down, all heart up, or alternating heart and bark makes no difference, they all tend to end up with a concave upper surface over time. So the better plan is to arrange the boards to deliver the most harmonious and pleasing appearance, letting heart and bark sides fall where they may.

 

[custard]

Hi i am quite new to woodworking and have recently started it up as a hobby with some general knowledge of it.
I have recently glued up a small table top approximately 350mm by 350mm it consists of 5 panels. Last week i got it all flat and square after it was glued together it was pretty much perfect so to my surprise i came back to it a week later and its warped slightly in the middle i am puzzled and pulling my hair out to why this has happened can anyone help please i know there is seasonal movement in hardwood but theres no way it should moved that much in a week. PS the wood is maple and walnut.

Many thanks

Paul

Did you leave it flat on your bench? If so the air can get to the upper surface and dry that, but not to the lower surface. Prop it up if it's to be left for a week so air can circulate all around. And leave your timber "in stick" for a few weeks in the workshop before starting work, if possible bring it down to thickness in increments over another couple of weeks, always taking roughly equal amounts off each face. A huge part of woodworking is just dealing with the inevitable movement of timber.

 

[Sgian Dubh]

Did you reverse the grain of the pieces? Heart side up, heart side down, heart side up ... ? That minimises cupping.

There's some superficial logic to that, but the practical reality is that table tops almost always tend to cup upwards no matter what you do. Study enough antiques and you see that all heart down, all heart up, or alternating heart and bark makes no difference, they all tend to end up with a concave upper surface over time. So the better plan is to arrange the boards to deliver the most harmonious and pleasing appearance, letting heart and bark sides fall where they may.

What the original question was about and what you've described custard is essentially the difference between distortion in recently worked wood (a recently made up panel), and distortion caused by moisture cycling and compression set. The first is most likely caused by any one of the factors described by others, e.g., one face exposed to changes in humidity and one face protected, such as might be the case if a panel is left resting with one face resting on a bench.

The latter, commonly seen in old furniture as you describe, is usually the result of repeated exposure to moisture in the air (or even actual wetting) of the upper surface whilst the underside is largely protected exposure to moisture.

Take, for example a somewhat extreme example, a traditional Victorian kitchen worktable of unfinished pine, that received regular scrubbing with hot water after food preparation. Each application of water to the top surface and the subsequent drying is a moisture cycle. The wood cells near the top surface of the wood adsorb a little water and swell, then dry and shrink again — the underside of the table top always remained relatively dry as it was never soaked with so much water. Because the table tops were fixed down to stout rails in the under framing they weren’t able to cup upwards freely in response to the wetting — convex side up. The dry underside, and the rails and/or bearers holding the top flat resist each swelling of the cells on the top side. The result is the cells near the upper surface gradually distort and collapse. Once they have collapsed they will never again, under normal circumstances in service, revert to their original shape and the upward facing concavity becomes permanent. Slainte.

 

[Phillbo87]

Thanks for all the responses they really helped. Yes i had reversed the grain of the pieces. I think it must of warped slightly because i just left it flat on my bench and its quite cold in the shed where i do my woodwork. The warp in the middle of wood is only slight so i should be able to salvage the table top if i can't its not the end of the world i was more bothered about not knowing why the warping had happened but thanks to your responses i have a better understanding of it now.

Many Thanks
Paul

 

[lurker]

Thanks for all the responses they really helped. Yes i had reversed the grain of the pieces. I think it must of warped slightly because i just left it flat on my bench and its quite cold in the shed where i do my woodwork. The warp in the middle of wood is only slight so i should be able to salvage the table top if i can't its not the end of the world i was more bothered about not knowing why the warping had happened but thanks to your responses i have a better understanding of it now.

Many Thanks
Paul

Thats a pragmatic reponse :lol:
With luck it will be so slight no one but you will know.

The weather we have been having recently I'd be avoiding any glue ups of this nature in my cold workshop.