Beech block worktop bow problem

[dexteria]

Hi all,

I've had some beech block worktop in my workshop for a couple of weeks now. On Friday I removed the plastic wrapper and cut the worktop into 3 lengths. One of these was about 600mm long and two others 1200mm.

Today I have noticed that the short piece has a front to back bow of about 25mm in the centre. I have plenty of other wood (oak, ash, maple, scots pine....) in the same workshop area wich exhibits no warpage. Has anyone experienced this before? I thought Beech block shouldn't bow like this?

Any advice appreciated.

TIA

Mark

 

[orangetlh]

Beech is one of the worst timbers for movement. try spraying a small amount of water on the concave side with one of those garden centre spray bottle things, should return it somewhere near.

 

[ByronBlack]

also, if you plane a small amount out of the convex side, this can release some tension and sometime reduce the amount of bow - I did this recently with some staves that I cut for a workbench top.

 

[OllyK]

Had the exact same problem with an offcut left over from the kitchen. Put it up on the rafter in the garage with the bow facing up and stacked a load of weight on top of it. I then forgot about it for a couple of months and came across it again this weekend - it's nice and flat again!

 

[dexteria]

I've clamped it flat for now. I'll leave it for a couple of days. Failing that I'll try the water spray and then planing.

Thanks for the advice.

Mark

 

[dexteria]

Hi all,

The clamping alone didn't work so I tried the water spray trick and it worked a treat.

Cheers

Mark

 

[motownmartin]

Hi all,

The clamping alone didn't work so I tried the water spray trick and it worked a treat.

Cheers

Mark

Let us know what happens when it dries out.

Martin

 

[mel]

you could try stress relieving it with a simple saw cut
use a thin curf blade and cut approx half the material away
avoid the end of the board if it will be seen

just a thought

hth
mel

 

[Sgian Dubh]

This all has to do with how wood reacts to changes in relative humidity (RH.) There's a good chance the wood was originally kiln dried to about 7% or 8% MC and then processed into a worktop fairly shortly after that. Then, to retain the MC at as low a level as possible it was shrink wrapped to reduce exposure to high RH numbers during storage and transport to the retail outlet and, finally, into a customer's house.

Removing the shrink wrapping suddenly exposed the wood to typical garage/workshop conditions in which there is no climate control and average RH is likely at this time of year to be about 60-65%. This equates to, given time, a wood equilibrium moisture content (EMC) between about 11% and 12.5%. The key phrase is, 'given time.' The take up or loss of moisture from wood is affected by hysteresis (a time lag.)

It's a possiblity that the piece that cupped was cut and laid flat on a horizontal surface thus exposing the upper surface to a higher RH and shielding the other from it. The top surface absorbs moisture and swells and the lower surface doesn't, so the result is cupping across the width with the convex face up. The other two parts might have been placed so that air could circulate all around them thus reducing the likelihood of cupping occurring. Obviously I have no idea what happened to the parts after they were cut, but what I've suggested is a realistic scenario.

Placing the cupped piece so that air can circulate freely all round will allow it to equalise its moisture content on both faces creating a balanced moisture gradient throughout the thickness. This will give the board the best long term chance to straighten out. A quick wipe over with a damp cloth on the concave side, as has been suggested, may help in the short term. It's hard to know if the piece will ever fully flatten, but if the other pieces from the same length remain flat, then this piece should eventually match their condition. Slainte.

 

[harvestbarn]

I would suspect the garage humidity has been nearer 80% for the last month or two due to the unusually extremely wet weather for such a long period. That is assuming the garage space has not been heated or dehumidified.

 

[custard]

All this business with squirting water and weights is just desperate measures in extreme circumstances when there's nothing else to do and so nothing to lose.

After forty years woodworking the policy in my workshop is simple, if a piece of wood persistently demonstrates that it doesn't want to behave itself then it goes on the wood burner pile. End of. I'm not risking using it in a furniture build because hard won experience has taught me it'll just cause me more problems later on.

Yes, Beech is a well known offender in this respect, but treat each piece of timber on it's own merits irrespective of the species. The least stable piece of Cuban Mahogany or Rosewood is still less stable than the most stable piece of Beech.

 

[novocaine]

just off the top of my head, but I'd suspect that if it was bent in 2007 it is now completely warped and quite possibly crispy and black having been ripped out and burned.

 

[Phil Pascoe]

Yes. I'm not sure that 80% humidity eight years later will affect it much.

 

[blackrodd]

just off the top of my head, but I'd suspect that if it was bent in 2007 it is now completely warped and quite possibly crispy and black having been ripped out and burned.

+1 More for the above, Nasty, nasty, beech even formed from "staves" should be kept in the fixing area to settle to the M/C of that area, cutting in the workshop and leaving in there is never a good idea, for any time at all.
Checking the wrapper for damage is advised, as it is wrapped and sealed in the factory and will suck up moisture really swiftly once opened.
If it's for you're self then I'd suggest a slitting saw and fixing, But as Custard says for a bespoke kitchen it's wise not to chance you're luck and reputation.
Regards Rodders

 

[beganasatree]

Hi Mark,
In the garage/workshop I have oak.zebrano wenge.beech and iroko work top offcuts and guess which one has bowed ??

Peter.

 

[Giff]

Iroko ?