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Default How to repair warped table top?

Planks (a light wood?) that make up the top of a small table are weather
warped. "Cupped" upward.

This isn't meant to be a centerpiece of the home, but it would be nice to
make it presentable again.

What's the usual repair recommended for such a condition?

Tools available: the usual drills and hand tools; table saw; router; belt
sander; palm sander; paint gun and compressor.

Suggestions welcome.

Thanks.

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Default How to repair warped table top?

Paul Conners wrote:
Planks (a light wood?) that make up the top of a small table are
weather warped. "Cupped" upward.

This isn't meant to be a centerpiece of the home, but it would be
nice to make it presentable again.

What's the usual repair recommended for such a condition?


Replace the boards. And put them so if they cup they will cup with the
center up. Fasten in the center and keep painted/varnished.
_____________

Tools available: the usual drills and hand tools; table saw; router;
belt sander; palm sander; paint gun and compressor.

Suggestions welcome.


Well, you could ....

a) plane down the boards to make them flat on the surface

b) if thin/narrow enough, bend them down and fasten

c) if not thin enough, remove and rip one or more kerfs on underside, put
glue in kerfs, bend flat.



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....a help file of info about MP3s, recording from
LP/cassette and tips & tricks on this and that.
Get it at http://mysite.verizon.net/xico



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Default How to repair warped table top?

On Feb 17, 12:55*am, Paul Conners wrote:
Planks (a light wood?) that make up the top of a small table are weather
warped. "Cupped" upward.

This isn't meant to be a centerpiece of the home, but it would be nice to
make it presentable again.

What's the usual repair recommended for such a condition?

Tools available: the usual drills and hand tools; table saw; router; belt
sander; palm sander; paint gun and compressor.

Suggestions welcome.

Thanks.


Depends on the amount of cup and the edges of the table. My wife
inherited an attractive elm claw foot from her mom. It had a similar
problem and one of the glue joints had failed too. I removed it from
the legs, removed the edge trim, sawed through the failed glue joint
and glued it back together. Before gluing I took a thin pass through
a thickness planer to level the top out again. Came out looking
good. If you don't have a planer, search around for a friend or
school that does.

RonB
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Default How to repair warped table top?

On Feb 16, 10:55*pm, Paul Conners wrote:
Planks (a light wood?) that make up the top of a small table are weather
warped. "Cupped" upward.

This isn't meant to be a centerpiece of the home, but it would be nice to
make it presentable again.

What's the usual repair recommended for such a condition?

Tools available: the usual drills and hand tools; table saw; router; belt
sander; palm sander; paint gun and compressor.

Suggestions welcome.

Thanks.


Very hard to say how I would address it without seeing a picture. Can
you post a pic somwhere? Be careful if you plan to try and address it
with a planer because depending on the defect the planer rollers can
sometimes just hold it flat while it planes it, then aftewards it
rools right back into it's curl and you have a nice flat but curled
surface still.
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Default How to repair warped table top?

On 2/17/2012 12:55 AM, Paul Conners wrote:
Planks (a light wood?) that make up the top of a small table are weather
warped. "Cupped" upward.

This isn't meant to be a centerpiece of the home, but it would be nice to
make it presentable again.

What's the usual repair recommended for such a condition?

Tools available: the usual drills and hand tools; table saw; router; belt
sander; palm sander; paint gun and compressor.

Suggestions welcome.

Thanks.


I like to start this type of conversation by saying, "you're not happy
with it the way it is now, are you?" or "it doesn't work now, does it?".
I guess we can't hurt too bad.

I would remove the top. On a nice spring day I would lay it on the
grass with the humped side up. Let it sit there a day preferably with
some sunshine. The piece has probably gotten wet at some point and the
top dried quicker and pulled the warp. I am suggesting you try to
equalize the moisture throughout the piece. I'm thinking you will see
some substantial improvement after a day of absorbing ground moisture on
the shrunken side and air/sun drying on the top side. I would them give
it lots of weight on a flat table surface, not on the concrete patio or
garage floor. After a week, see what you have.

--


___________________________________

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Dan G
remove the seven


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Default How to repair warped table top?

I would remove the top. On a nice spring day I would lay it on the
grass with the humped side up. Let it sit there a day preferably with
some sunshine. The piece has probably gotten wet at some point and the
top dried quicker and pulled the warp. I am suggesting you try to
equalize the moisture throughout the piece. I'm thinking you will see
some substantial improvement after a day of absorbing ground moisture on
the shrunken side and air/sun drying on the top side. I would them give
it lots of weight on a flat table surface, not on the concrete patio or
garage floor. After a week, see what you have.
[Dan G]


I like your suggestions. The lawn and sunshine are readily available. But the
only large flat surface is the garage floor. And weight? Hmm... 2 front
wheels of the Toyota come to mind...

Thanks.

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Default How to repair warped table top?

In ,
Paul Conners typed:
Planks (a light wood?) that make up the top of a small
table are weather warped. "Cupped" upward.

This isn't meant to be a centerpiece of the home, but it
would be nice to make it presentable again.

What's the usual repair recommended for such a condition?

Tools available: the usual drills and hand tools; table
saw; router; belt sander; palm sander; paint gun and
compressor.

Suggestions welcome.

Thanks.


Find someone with a planer and have them smooth it out for you into a flat
surface.


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Default How to repair warped table top?

On 2/18/2012 12:42 PM, Paul Conners wrote:
I would remove the top. On a nice spring day I would lay it on the
grass with the humped side up. Let it sit there a day preferably with
some sunshine. The piece has probably gotten wet at some point and the
top dried quicker and pulled the warp. I am suggesting you try to
equalize the moisture throughout the piece. I'm thinking you will see
some substantial improvement after a day of absorbing ground moisture on
the shrunken side and air/sun drying on the top side. I would them give
it lots of weight on a flat table surface, not on the concrete patio or
garage floor. After a week, see what you have.
[Dan G]


I like your suggestions. The lawn and sunshine are readily available. But the
only large flat surface is the garage floor. And weight? Hmm... 2 front
wheels of the Toyota come to mind...


I thought his suggestion ingenious as well. How about that Toyota, an
appropriately-sized sheet of 3/4" plywood (make a sandwich of your
"moistened" top) and a piece of 2x10 as a caul?

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Default How to repair warped table top?

Paul Conners wrote:

Planks (a light wood?) that make up the top of a small table are weather
warped. "Cupped" upward.

This isn't meant to be a centerpiece of the home, but it would be nice to
make it presentable again.

What's the usual repair recommended for such a condition?

Tools available: the usual drills and hand tools; table saw; router; belt
sander; palm sander; paint gun and compressor.

Suggestions welcome.

Thanks.


Just a note - cupping takes place towards the moisture not away from it.
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Default How to repair warped table top?

Just a note - cupping takes place towards the moisture not away from it.

Just to clarify: the concave side is moist, and the convex side is dry?



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Default How to repair warped table top?

Paul Conners wrote:

Just a note - cupping takes place towards the moisture not away from it.



Just to clarify: the concave side is moist, and the convex side is dry?

Yes.
Table top looks like a U (not as drastic I hope). Top got wet while the
underside remained drier. When it dried out the compressed fibers
(caused be the dry side restricting even swelling of the wet side)
distort it... according to the books

As mentioned, a possible sollution is to wet it all down lay it on
stickers and put weight on it to dry.

The "proper" method for an antique is to router out the underside and
replace with hardboard. That leaves the original top surface while
providing a flat base for it. Something I probably would not have the
nerve to do.

Mike
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Default How to repair warped table top?

On 2/22/2012 12:05 AM, Michael Joel wrote:
Paul Conners wrote:

Just a note - cupping takes place towards the moisture not away from it.



Just to clarify: the concave side is moist, and the convex side is dry?

Yes.



Not necessarily ... and AAMOF, and depending upon the grain and the way
the wood was cut off the tree, it more likely to be just the opposite of
what you stated ... the concave side being the dry side, and the convex
the moist.

There are indeed some exception with certain grain patterns due to the
way the wood was cut from the log (plain sawn, rift sawn, etc.), or if
laminated, but mostly wood cups and checks parallel to the grain and to
the drier side.

Excellent example is the cupping of hardwood floors, which "cup"
(concave side up) when wet from the underneath ... dry on the top, wet
on bottom ... one of the main reasons why a moisture barrier is always
used _beneath_ a hardwood floor.

Another hole in your balloon ... leaving a board to dry out in the sun,
The concave side is drier from exposure to the sun and heat, and, once
again, the board generally cups toward the dry side.

Try this by laying a board on wet grass before the morning sun hits on
sunny day, check it out by noon.

Here is indeed, "according to the books":
http://www.fpl.fs.fed.us/documnts/fp...chapter_16.pdf 16-6:

quote
Wood warmed by the sun experiences a virtual RH far below the ambient
RH. The surface dries faster than the rest of the lumber. This is why
cupping and checking often occur on decking boards; the top surface is
much drier than the rest of the board. Shrinkage of the top surface
commensurate with this dryness causes cupping and checking parallel to
the grain
/quote


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As mentioned, a possible sollution is to wet it all down lay it on
stickers and put weight on it to dry.
...
Mike


What are "stickers"?

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Paul Conners wrote:
As mentioned, a possible sollution is to wet it all down lay it on
stickers and put weight on it to dry.
...
Mike


What are "stickers"?


Google is your friend...

Man - does *anybody* do any kind of looking on their own any more?

--

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Default How to repair warped table top?

On 2/22/2012 11:58 AM, Paul Conners wrote:
....

What are "stickers"?


goatheads, sandburs, wavy thistle, ...

Sorry, couldn't help it.
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Default How to repair warped table top?

Swingman wrote:
On 2/22/2012 12:05 AM, Michael Joel wrote:

Paul Conners wrote:

Just a note - cupping takes place towards the moisture not away from
it.



Just to clarify: the concave side is moist, and the convex side is dry?

Yes.




Not necessarily ... and AAMOF, and depending upon the grain and the way
the wood was cut off the tree, it more likely to be just the opposite of
what you stated ... the concave side being the dry side, and the convex
the moist.

There are indeed some exception with certain grain patterns due to the
way the wood was cut from the log (plain sawn, rift sawn, etc.), or if
laminated, but mostly wood cups and checks parallel to the grain and to
the drier side.

Excellent example is the cupping of hardwood floors, which "cup"
(concave side up) when wet from the underneath ... dry on the top, wet
on bottom ... one of the main reasons why a moisture barrier is always
used _beneath_ a hardwood floor.

Another hole in your balloon ... leaving a board to dry out in the sun,
The concave side is drier from exposure to the sun and heat, and, once
again, the board generally cups toward the dry side.

Try this by laying a board on wet grass before the morning sun hits on
sunny day, check it out by noon.

Here is indeed, "according to the books":
http://www.fpl.fs.fed.us/documnts/fp...chapter_16.pdf 16-6:

quote
Wood warmed by the sun experiences a virtual RH far below the ambient
RH. The surface dries faster than the rest of the lumber. This is why
cupping and checking often occur on decking boards; the top surface is
much drier than the rest of the board. Shrinkage of the top surface
commensurate with this dryness causes cupping and checking parallel to
the grain
/quote



Sorry but I believe what I said to still be right.

While grain of course will have effects the cupping will take place
towards the moist side (or away from the compression pressure might also
be a way to say it). Take a look at porches or decks, do you seen any
cupped down? Fave you ever found a table top that cupped down?

Your wood floor - is it cupping because it is moist underneath or
because of the mopping and drying taking place above? as for the board
on the lawn - don't know, would have to try it.

Your quote - Is it indeed the sun causing the surface to dry faster or
is it in fact that the problem is not visual until the surface dries?

I will explain it as one of the books due (please recall I said this was
according to the books - not neccessarily the truth - I believe much of
the things "known" are not the truth of what is happening, but only what
we as humans can guess at/or comprehend with our limited knowledge).

Wood cells normally want to swell and then shrink back to their normal
shape and size. When something restricts this the swelling continues on
uncompressed sides (i.e. the bottom of the board, or anywhere else it is
not wet/or drier). This forces the cells into more of an oval shape
instead of their original shape. When they shrink from drying this shape
is not shanged so the compressed sides of the cell (we will call it the
width) ends up smaller than it used to be. As this is repeated we end up
with cupping/warping/checks/etc..

I can never recall seeing a board that was cupped in any direction
except on the side effected by changes in moisture.

Mike
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Google is your friend...

Sticker
A sticker is a type of a piece of paper or plastic, adhesive, sticky on
one side, and usually with a design on the other.

Stickers, Bumper Stickers - Sticker Giant
Stickers made easy. 26,000 bumper sticker designs in stock. Custom
sticker

Stickers - Shop for a new Custom Stickers
Political stickers, art stickers, funny stickers and millions more!
Highest

Stickers Galore
Stickers Galore offers an incredibly large selection of stickers for \

123stickers.com - Custom vinyl stickers | Custom Banners ...
Custom Vinyl Stickers | Custom T-shirts | Custom Banners. Low minimum
custom

Then I tried "sticker wood" and got this and the like:

http://www.ebay.com/sch/items/?_nkw=...w=&_mPrRngCbx=
1&_udlo=&_udhi=&_sop=12&_fpos=&_fspt=1&_sadis=&LH_ CAds=

There comes a point where the flaming of "Don't you use Google?" is worth
it...

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Default How to repair warped table top?

Paul Conners wrote:
As mentioned, a possible sollution is to wet it all down lay it on
stickers and put weight on it to dry.
...
Mike



What are "stickers"?

Sticks of wood (lumber). Usually they are used in stacked lumber to keep
the wood separated for air flow - and flat.

I did not mention that you would want a flat surface under the stickers.

Mike
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Default How to repair warped table top?

On 2/22/2012 1:09 PM, Michael Joel wrote:
Swingman wrote:
On 2/22/2012 12:05 AM, Michael Joel wrote:

Paul Conners wrote:

Just a note - cupping takes place towards the moisture not away
from it.



Just to clarify: the concave side is moist, and the convex side is dry?

Yes.




Not necessarily ... and AAMOF, and depending upon the grain and the
way the wood was cut off the tree, it more likely to be just the
opposite of what you stated ... the concave side being the dry side,
and the convex the moist.

There are indeed some exception with certain grain patterns due to the
way the wood was cut from the log (plain sawn, rift sawn, etc.), or if
laminated, but mostly wood cups and checks parallel to the grain and
to the drier side.

Excellent example is the cupping of hardwood floors, which "cup"
(concave side up) when wet from the underneath ... dry on the top, wet
on bottom ... one of the main reasons why a moisture barrier is always
used _beneath_ a hardwood floor.

Another hole in your balloon ... leaving a board to dry out in the
sun, The concave side is drier from exposure to the sun and heat, and,
once again, the board generally cups toward the dry side.

Try this by laying a board on wet grass before the morning sun hits on
sunny day, check it out by noon.

Here is indeed, "according to the books":


http://www.fpl.fs.fed.us/documnts/fp...chapter_16.pdf


quote
Wood warmed by the sun experiences a virtual RH far below the ambient
RH. The surface dries faster than the rest of the lumber. This is why
cupping and checking often occur on decking boards; the top surface is
much drier than the rest of the board. Shrinkage of the top surface
commensurate with this dryness causes cupping and checking parallel to
the grain
/quote



Sorry but I believe what I said to still be right.


Did you bother to even read the supporting evidence I provided
disproving your unequivocal contention, first above?

I will explain it as one of the books due (please recall I said this was
according to the books - not neccessarily the truth


It is indeed "not necessarily the truth", as I clearly outlined above,
complete with a cite as to the an explanation for why your statement is
not necessarily the case.

By all means, offer a cite that supports your contention to the contrary.

I believe much of
the things "known" are not the truth of what is happening, but only what
we as humans can guess at/or comprehend with our limited knowledge).


Yes, and as a result, that attitude arguably insures that your knowledge
in this regard will remain limited.

Wood cells normally want to swell and then shrink back to their normal
shape and size. When something restricts this the swelling continues on
uncompressed sides (i.e. the bottom of the board, or anywhere else it is
not wet/or drier). This forces the cells into more of an oval shape
instead of their original shape. When they shrink from drying this shape
is not shanged so the compressed sides of the cell (we will call it the
width) ends up smaller than it used to be. As this is repeated we end up
with cupping/warping/checks/etc..


The above is either so poorly worded as to be useless in defining your
contention, or the result of a total misunderstanding of the effects of
moisture and humidity on the dimensional instability of wood.

It's really impossible to tell which?

I can never recall seeing a board that was cupped in any direction
except on the side effected by changes in moisture.


Again, too loosely worded to be of much use in defining the problem ...
and your admission that you have "never recalled" seeing that, is
certainly no proof of your argument.

Yes, it is indeed this _differential_ in moisture content between
opposite faces that causes the phenomenon of cupping, but not
necessarily for the reason you unequivocally stated first above.

Simply put, cupping is most often the result of the opposite (convex)
side being moist, and the cupped (concave) side being drier ... the
exact opposite of your unequivocal statement.

IOW, your understanding is mostly backwards of the actual effect of
moisture on wood, with the exceptions I noted above. You will certainly
want to do your homework, and provide some supporting evidence to the
contrary, if you want to continue a reasonable discussion of the issue.

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Swingman wrote:

On 2/22/2012 12:05 AM, Michael Joel wrote:

Paul Conners wrote:

SNIP


Just 2 mor cents...

Grain of course plays a part is how the reaction takes place, but as you
said "but mostly wood cups and checks parallel to the grain and to the
drier side".

As my previous post metnions - never seen a floor/table/deck cup down.

But I don't want to argue it. As said - I am simply repeating it from
information I have read. I doubt anyone knows for sure the real reasons
for it all.
Mike


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Default How to repair warped table top?

Swingman wrote:

On 2/22/2012 1:09 PM, Michael Joel wrote:

Swingman wrote:

On 2/22/2012 12:05 AM, Michael Joel wrote:

Paul Conners wrote:

Just a note - cupping takes place towards the moisture not away
from it.




Just to clarify: the concave side is moist, and the convex side is
dry?

Yes.




Not necessarily ... and AAMOF, and depending upon the grain and the
way the wood was cut off the tree, it more likely to be just the
opposite of what you stated ... the concave side being the dry side,
and the convex the moist.

There are indeed some exception with certain grain patterns due to the
way the wood was cut from the log (plain sawn, rift sawn, etc.), or if
laminated, but mostly wood cups and checks parallel to the grain and
to the drier side.

Excellent example is the cupping of hardwood floors, which "cup"
(concave side up) when wet from the underneath ... dry on the top, wet
on bottom ... one of the main reasons why a moisture barrier is always
used _beneath_ a hardwood floor.

Another hole in your balloon ... leaving a board to dry out in the
sun, The concave side is drier from exposure to the sun and heat, and,
once again, the board generally cups toward the dry side.

Try this by laying a board on wet grass before the morning sun hits on
sunny day, check it out by noon.

Here is indeed, "according to the books":



http://www.fpl.fs.fed.us/documnts/fp...chapter_16.pdf


quote
Wood warmed by the sun experiences a virtual RH far below the ambient
RH. The surface dries faster than the rest of the lumber. This is why
cupping and checking often occur on decking boards; the top surface is
much drier than the rest of the board. Shrinkage of the top surface
commensurate with this dryness causes cupping and checking parallel to
the grain
/quote



Sorry but I believe what I said to still be right.



Did you bother to even read the supporting evidence I provided
disproving your unequivocal contention, first above?

I will explain it as one of the books due (please recall I said this was
according to the books - not neccessarily the truth



It is indeed "not necessarily the truth", as I clearly outlined above,
complete with a cite as to the an explanation for why your statement is
not necessarily the case.

By all means, offer a cite that supports your contention to the contrary.

I believe much of
the things "known" are not the truth of what is happening, but only what
we as humans can guess at/or comprehend with our limited knowledge).



Yes, and as a result, that attitude arguably insures that your knowledge
in this regard will remain limited.

Wood cells normally want to swell and then shrink back to their normal
shape and size. When something restricts this the swelling continues on
uncompressed sides (i.e. the bottom of the board, or anywhere else it is
not wet/or drier). This forces the cells into more of an oval shape
instead of their original shape. When they shrink from drying this shape
is not shanged so the compressed sides of the cell (we will call it the
width) ends up smaller than it used to be. As this is repeated we end up
with cupping/warping/checks/etc..



The above is either so poorly worded as to be useless in defining your
contention, or the result of a total misunderstanding of the effects of
moisture and humidity on the dimensional instability of wood.

It's really impossible to tell which?

I can never recall seeing a board that was cupped in any direction
except on the side effected by changes in moisture.



Again, too loosely worded to be of much use in defining the problem ...
and your admission that you have "never recalled" seeing that, is
certainly no proof of your argument.

Yes, it is indeed this _differential_ in moisture content between
opposite faces that causes the phenomenon of cupping, but not
necessarily for the reason you unequivocally stated first above.

Simply put, cupping is most often the result of the opposite (convex)
side being moist, and the cupped (concave) side being drier ... the
exact opposite of your unequivocal statement.

IOW, your understanding is mostly backwards of the actual effect of
moisture on wood, with the exceptions I noted above. You will certainly
want to do your homework, and provide some supporting evidence to the
contrary, if you want to continue a reasonable discussion of the issue.



Ok. Whatever you would like to make it. I have no need to argue.
I think my sentences were clear enough.

You also call into question whether or not I even undestand moisture -
and that I will not be able to learn (if I don't).

I do believe for some reason you feel offended and seem to have a chip -
but that is fine too.

You have decided what you will take for the answer - nothing I say or do
will change it.

Mike
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Default How to repair warped table top?

On 2/22/2012 2:11 PM, Michael Joel wrote:
Swingman wrote:

On 2/22/2012 12:05 AM, Michael Joel wrote:

Paul Conners wrote:

SNIP


Just 2 mor cents...

Grain of course plays a part is how the reaction takes place, but as you
said "but mostly wood cups and checks parallel to the grain and to the
drier side".

As my previous post metnions - never seen a floor/table/deck cup down.

But I don't want to argue it. As said - I am simply repeating it from
information I have read. I doubt anyone knows for sure the real reasons
for it all.


You don't want to argue because you were mistaken, charitably, either in
your wording, or your understanding.

And you are very mistaken in your contention that you "doubt anyone
knows for sure" ... a first semester, college level, Botany 101 class
would prove to you that this is well understood, and well documented
with empirical evidence.

For your future benefit, and so this ends on an instructive note, you
will certainly want to explore the definitive work on the matter:

http://www.amazon.com/UNDERSTANDING-.../dp/B000UQH160

Every woodworker can learn something from reading Hoadley, guaranteed.

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On 2/22/2012 2:19 PM, Michael Joel wrote:
Swingman wrote:



moisture on wood, with the exceptions I noted above. You will
certainly want to do your homework, and provide some supporting
evidence to the contrary, if you want to continue a reasonable
discussion of the issue.



Ok. Whatever you would like to make it. I have no need to argue.
I think my sentences were clear enough.

You also call into question whether or not I even undestand moisture -
and that I will not be able to learn (if I don't).

I do believe for some reason you feel offended and seem to have a chip -
but that is fine too.

You have decided what you will take for the answer - nothing I say or do
will change it.



To the contrary, and unlike you ... I will certainly read any supporting
evidence you have to support your position.




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Swingman wrote:
You don't want to argue because you were mistaken, charitably, either in
your wording, or your understanding.

And you are very mistaken in your contention that you "doubt anyone
knows for sure" ... a first semester, college level, Botany 101 class
would prove to you that this is well understood, and well documented
with empirical evidence.

For your future benefit, and so this ends on an instructive note, you
will certainly want to explore the definitive work on the matter:

http://www.amazon.com/UNDERSTANDING-.../dp/B000UQH160

Every woodworker can learn something from reading Hoadley, guaranteed.


See - that is why I get pulled back in. Because the logic is so illogical.

If I said I don't believe they really know what is happening - you say
take a "first semester, college level, Botany 101 class
would prove" - The only thing it would prove is they believe it. Very
circular thinking (as the "scientists" would say).

That will be the last think I desire to say on the subject to you. You
may continue to deride me if you like.

Mike
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On 2/22/2012 2:28 PM, Michael Joel wrote:
Swingman wrote:



That will be the last think I desire to say on the subject to you. You
may continue to deride me if you like.


You are wrong again ... it is not you being derided, It is you showing
up here, making a statement that is misleading, and taking exception to
being corrected (and very nicely and politely so, if you read my first post)

What we don't particularly care for here is misleading information, so
pardon me if I don't feel sorry for your above whining as somehow being
a "victim".


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Sticks of wood (lumber). Usually they are used in stacked lumber to keep
the wood separated for air flow - and flat.

I did not mention that you would want a flat surface under the stickers.

Mike


Thank you Mike.

Three or four 2in x 2in sticks for a 36in x 48in table top?

It will be placed on a concrete slab apron in front of the garage. No cracks
or obvious defects in the slab.

Thanks.

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On 2/22/2012 2:28 PM, Michael Joel wrote:
Swingman wrote:
You don't want to argue because you were mistaken, charitably, either
in your wording, or your understanding.

And you are very mistaken in your contention that you "doubt anyone
knows for sure" ... a first semester, college level, Botany 101 class
would prove to you that this is well understood, and well documented
with empirical evidence.

For your future benefit, and so this ends on an instructive note, you
will certainly want to explore the definitive work on the matter:

http://www.amazon.com/UNDERSTANDING-.../dp/B000UQH160

Every woodworker can learn something from reading Hoadley, guaranteed.


See - that is why I get pulled back in. Because the logic is so illogical.

If I said I don't believe they really know what is happening - you say
take a "first semester, college level, Botany 101 class
would prove" - The only thing it would prove is they believe it. Very
circular thinking (as the "scientists" would say).

....

Well, that's self-serving to the max. You might as well say that the
physicists on believe Newton's Principles; after all, it's "only" a theory.

I suggest you do read Hoadley (or any of several references from the US
Forest Products Lab, these can be downloaded at no cost); specifically
Chap 4, "Wood and Water".

The short story is---wood shrinks as it dries and it does so
non-uniformly. The tangential/radial shrinkage ratio from green to
oven-dry has been measured for some hundreds of species and averages
about 2 (roughly an average of 8%/4% T/R) but shows a significant
variation between species of from just barely above 1:1 to highs
approaching 3:1. The higher the ratio the more the particular would
will distort as it is dried as the relative shrinkage in the two
directions competes at a different rate.

The difference between tangential and radial shrinkage isn't random nor
magic; it's caused by the anatomical structure, principally the effect
of wood rays whose lengthwise axes are oriented radially outward.
Species w/ more predominant rays are more stable.

Over the range of moisture content shrinkage is roughly proportional to
moisture loss. This doesn't matter too much as raw lumber is dried; the
roughsawn stock is oversize to begin with and if dried uniformly will be
stable after it is milled given a uniform environment. This is why it
is so important to finish both sides of a furniture panel, say--if one
side is finished and the other not, differential moisture absorption is
highly likely to cause movement.

Cupping after the fact is owing to one of two causes--either the piece
wasn't at equilibrium to begin with and dried after milling with the
resultant change in dimension as determined by the species' particular
T/R ratio and the percentage change in moisture.

The second is that the piece has subsequently absorbed moisture and
therefore grown. The relative amount in the direction is also dependent
on T/R and how uniform (or un-uniform) the moisture absorption is.

Cupping in flatsawn boards results in concavity away from the pith, the
result of greater tangential than radial shrinkage. The magnitude is
greater as the location of the board from the original trunk is closer
to the pith on a surface. This face is completely radial while the
opposite is tangential in the portion across from the location of the
pith and will therefore shrink at twice the rate. Woodworkers tend to
say the "rings flatten out" which an easy way to remember the direction
the board will cup but the reason for the cup has virtually nothing to
do w/ the growth rings themselves.

Cup is reversible on swelling which is why the idea of wetting is given
as a cure. Of course, the end then has to be to get the whole board in
equilibrium again at that point which goes back to point a) above--if
the piece was milled in inequilibrium, it's an insoluble problem w/o
mechanical repair.

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On 2/22/2012 3:36 PM, dpb wrote:
On 2/22/2012 2:28 PM, Michael Joel wrote:
Swingman wrote:
You don't want to argue because you were mistaken, charitably, either
in your wording, or your understanding.

And you are very mistaken in your contention that you "doubt anyone
knows for sure" ... a first semester, college level, Botany 101 class
would prove to you that this is well understood, and well documented
with empirical evidence.

For your future benefit, and so this ends on an instructive note, you
will certainly want to explore the definitive work on the matter:

http://www.amazon.com/UNDERSTANDING-.../dp/B000UQH160

Every woodworker can learn something from reading Hoadley, guaranteed.


See - that is why I get pulled back in. Because the logic is so illogical.

If I said I don't believe they really know what is happening - you say
take a "first semester, college level, Botany 101 class
would prove" - The only thing it would prove is they believe it. Very
circular thinking (as the "scientists" would say).

...

Well, that's self-serving to the max. You might as well say that the physicists
on believe Newton's Principles; after all, it's "only" a theory.

I suggest you do read Hoadley (or any of several references from the US Forest
Products Lab, these can be downloaded at no cost); specifically Chap 4, "Wood
and Water".

The short story is---wood shrinks as it dries and it does so non-uniformly. The
tangential/radial shrinkage ratio from green to oven-dry has been measured for
some hundreds of species and averages about 2 (roughly an average of 8%/4% T/R)
but shows a significant variation between species of from just barely above 1:1
to highs approaching 3:1. The higher the ratio the more the particular would
will distort as it is dried as the relative shrinkage in the two directions
competes at a different rate.

The difference between tangential and radial shrinkage isn't random nor magic;
it's caused by the anatomical structure, principally the effect of wood rays
whose lengthwise axes are oriented radially outward. Species w/ more
predominant rays are more stable.

Over the range of moisture content shrinkage is roughly proportional to
moisture loss. This doesn't matter too much as raw lumber is dried; the
roughsawn stock is oversize to begin with and if dried uniformly will be stable
after it is milled given a uniform environment. This is why it is so important
to finish both sides of a furniture panel, say--if one side is finished and the
other not, differential moisture absorption is highly likely to cause movement.

Cupping after the fact is owing to one of two causes--either the piece wasn't
at equilibrium to begin with and dried after milling with the resultant change
in dimension as determined by the species' particular T/R ratio and the
percentage change in moisture.

The second is that the piece has subsequently absorbed moisture and therefore
grown. The relative amount in the direction is also dependent on T/R and how
uniform (or un-uniform) the moisture absorption is.

Cupping in flatsawn boards results in concavity away from the pith, the result
of greater tangential than radial shrinkage. The magnitude is greater as the
location of the board from the original trunk is closer to the pith on a
surface. This face is completely radial while the opposite is tangential in the
portion across from the location of the pith and will therefore shrink at twice
the rate. Woodworkers tend to say the "rings flatten out" which an easy way to
remember the direction the board will cup but the reason for the cup has
virtually nothing to do w/ the growth rings themselves.

Cup is reversible on swelling which is why the idea of wetting is given as a
cure. Of course, the end then has to be to get the whole board in equilibrium
again at that point which goes back to point a) above--if the piece was milled
in inequilibrium, it's an insoluble problem w/o mechanical repair.


Wow, nice explanation! Thanks for taking the time to write that up.

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Paul Conners wrote:
Sticks of wood (lumber). Usually they are used in stacked lumber to keep
the wood separated for air flow - and flat.

I did not mention that you would want a flat surface under the stickers.

Mike



Thank you Mike.

Three or four 2in x 2in sticks for a 36in x 48in table top?

It will be placed on a concrete slab apron in front of the garage. No cracks
or obvious defects in the slab.

Thanks.


Whatever will allow air movement and keep it basically flat (flat is
relative really - a wal-mart straight edge is "flat" - unless of course
you compare it to a $45.00 straight edge - which is more flat ).

Let me clarify (at the danger of possibly being accused of trying to
change tack) what I meant when you asked "concave moist side". I meant
yes - as in moist side that has dried. I did not mean simply the moist
side causes a cup - it would have been made moist while compression was
placed on it (i.e. the dry side) and then dry out (but it may also take
many many times of this before a cup is seen). Information that is only
needed if someone is interested - from books - and not even needed to be
mentioned to answer your OP - so I guess my headache was caused once
again be me

Mike
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On 2/22/2012 9:21 AM, Swingman wrote:
On 2/22/2012 12:05 AM, Michael Joel wrote:
Paul Conners wrote:

Just a note - cupping takes place towards the moisture not away from
it.


Just to clarify: the concave side is moist, and the convex side is dry?

Yes.



Well no not normally. The side that absorbs the moisture expands.



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On 2/22/2012 3:36 PM, dpb wrote:

The short story is---wood shrinks as it dries and it does so
non-uniformly. The tangential/radial shrinkage ratio from green to
oven-dry has been measured for some hundreds of species and averages
about 2 (roughly an average of 8%/4% T/R) but shows a significant
variation between species of from just barely above 1:1 to highs
approaching 3:1. The higher the ratio the more the particular would will
distort as it is dried as the relative shrinkage in the two directions
competes at a different rate.

The difference between tangential and radial shrinkage isn't random nor
magic; it's caused by the anatomical structure, principally the effect
of wood rays whose lengthwise axes are oriented radially outward.
Species w/ more predominant rays are more stable.

Over the range of moisture content shrinkage is roughly proportional to
moisture loss. This doesn't matter too much as raw lumber is dried; the
roughsawn stock is oversize to begin with and if dried uniformly will be
stable after it is milled given a uniform environment. This is why it is
so important to finish both sides of a furniture panel, say--if one side
is finished and the other not, differential moisture absorption is
highly likely to cause movement.

Cupping after the fact is owing to one of two causes--either the piece
wasn't at equilibrium to begin with and dried after milling with the
resultant change in dimension as determined by the species' particular
T/R ratio and the percentage change in moisture.

The second is that the piece has subsequently absorbed moisture and
therefore grown. The relative amount in the direction is also dependent
on T/R and how uniform (or un-uniform) the moisture absorption is.

Cupping in flatsawn boards results in concavity away from the pith, the
result of greater tangential than radial shrinkage. The magnitude is
greater as the location of the board from the original trunk is closer
to the pith on a surface. This face is completely radial while the
opposite is tangential in the portion across from the location of the
pith and will therefore shrink at twice the rate. Woodworkers tend to
say the "rings flatten out" which an easy way to remember the direction
the board will cup but the reason for the cup has virtually nothing to
do w/ the growth rings themselves.

Cup is reversible on swelling which is why the idea of wetting is given
as a cure. Of course, the end then has to be to get the whole board in
equilibrium again at that point which goes back to point a) above--if
the piece was milled in inequilibrium, it's an insoluble problem w/o
mechanical repair.



Very well put and, as a result, that much more informative.

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On 2/22/2012 4:27 PM, Leon wrote:
On 2/22/2012 9:21 AM, Swingman wrote:
On 2/22/2012 12:05 AM, Michael Joel wrote:
Paul Conners wrote:

Just a note - cupping takes place towards the moisture not away from
it.


Just to clarify: the concave side is moist, and the convex side is dry?

Yes.



Well no not normally. The side that absorbs the moisture expands.


Don't look now, Bubba ... but I did not say that. LOL

I know ... it's Butch's fault!


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On 2/22/2012 1:09 PM, Michael Joel wrote:
Swingman wrote:
On 2/22/2012 12:05 AM, Michael Joel wrote:

Paul Conners wrote:

Just a note - cupping takes place towards the moisture not away
from it.



Just to clarify: the concave side is moist, and the convex side is dry?

Yes.




Not necessarily ... and AAMOF, and depending upon the grain and the
way the wood was cut off the tree, it more likely to be just the
opposite of what you stated ... the concave side being the dry side,
and the convex the moist.

There are indeed some exception with certain grain patterns due to the
way the wood was cut from the log (plain sawn, rift sawn, etc.), or if
laminated, but mostly wood cups and checks parallel to the grain and
to the drier side.

Excellent example is the cupping of hardwood floors, which "cup"
(concave side up) when wet from the underneath ... dry on the top, wet
on bottom ... one of the main reasons why a moisture barrier is always
used _beneath_ a hardwood floor.

Another hole in your balloon ... leaving a board to dry out in the
sun, The concave side is drier from exposure to the sun and heat, and,
once again, the board generally cups toward the dry side.

Try this by laying a board on wet grass before the morning sun hits on
sunny day, check it out by noon.

Here is indeed, "according to the books":
http://www.fpl.fs.fed.us/documnts/fp...chapter_16.pdf 16-6:

quote
Wood warmed by the sun experiences a virtual RH far below the ambient
RH. The surface dries faster than the rest of the lumber. This is why
cupping and checking often occur on decking boards; the top surface is
much drier than the rest of the board. Shrinkage of the top surface
commensurate with this dryness causes cupping and checking parallel to
the grain
/quote



Sorry but I believe what I said to still be right.

While grain of course will have effects the cupping will take place
towards the moist side (or away from the compression pressure might also
be a way to say it). Take a look at porches or decks, do you seen any
cupped down? Fave you ever found a table top that cupped down?


Have you ever seen deck boards or a table top that was not attached?
Given restrictions a board will bow in the direction that is not
restricted. Given no restrictions the surface absorbing moisture will
expand and that will not result in a concaved surface.




Your wood floor - is it cupping because it is moist underneath or
because of the mopping and drying taking place above? as for the board
on the lawn - don't know, would have to try it.


Absolutely the underneath side. You mop it and water goes down inside
the cracks to lower and side sections of of the board. Those surfaces
stay wet longer than the top surface. Then the edges expand and they cut
up but the surface has long since dried because of exposure.





Your quote - Is it indeed the sun causing the surface to dry faster or
is it in fact that the problem is not visual until the surface dries?


You are not thinking about all of the surfaces that have actually gotten
wet.





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Paul Conners wrote:
Google is your friend...


Sticker
A sticker is a type of a piece of paper or plastic, adhesive,
sticky on one side, and usually with a design on the other.

Stickers, Bumper Stickers - Sticker Giant
Stickers made easy. 26,000 bumper sticker designs in stock. Custom
sticker

Stickers - Shop for a new Custom Stickers
Political stickers, art stickers, funny stickers and millions
more! Highest

Stickers Galore
Stickers Galore offers an incredibly large selection of stickers
for \

123stickers.com - Custom vinyl stickers | Custom Banners ...
Custom Vinyl Stickers | Custom T-shirts | Custom Banners. Low
minimum custom

Then I tried "sticker wood" and got this and the like:

http://www.ebay.com/sch/items/?_nkw=...w=&_mPrRngCbx=
1&_udlo=&_udhi=&_sop=12&_fpos=&_fspt=1&_sadis=&LH_ CAds=

There comes a point where the flaming of "Don't you use Google?" is
worth it...


Here ya go then.... http://www.ca.uky.edu/agc/pubs/for/for55/for55.htm

I did a google search on the phrase "what is a sticker for drying wood" and
came up with this link and a bunch more.

--

-Mike-



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On 2/22/2012 4:32 PM, Swingman wrote:
On 2/22/2012 4:27 PM, Leon wrote:
On 2/22/2012 9:21 AM, Swingman wrote:
On 2/22/2012 12:05 AM, Michael Joel wrote:
Paul Conners wrote:

Just a note - cupping takes place towards the moisture not away from
it.


Just to clarify: the concave side is moist, and the convex side is
dry?

Yes.


Well no not normally. The side that absorbs the moisture expands.


Don't look now, Bubba ... but I did not say that. LOL

I know ... it's Butch's fault!



In know! I probably posted to the wrong person... Obviously. I knew
you were right.


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Well, that's self-serving to the max. You might as well say that the
physicists on believe Newton's Principles; after all, it's "only" a theory.

I suggest you do read Hoadley (or any of several references from the US
Forest Products Lab, these can be downloaded at no cost); specifically
Chap 4, "Wood and Water".

The short story is---...


Very interesting and valuable information. But I'm not sure it's particularly
relavent to my situation.

If it is warped, simply putting under great pressure (I have a few thousand
pounds of red bricks at hand), it's probably not pertinent *which* way it's
warped.

Placed on small square lumber and weighted, should give some good results.

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Here ya go then.... http://www.ca.uky.edu/agc/pubs/for/for55/for55.htm

I did a google search on the phrase "what is a sticker for drying wood" and
came up with this link and a bunch more.

-Mike-


Thanks. That helps.

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On 2/22/2012 9:31 PM, Paul Conners wrote:
....

Very interesting and valuable information. But I'm not sure it's particularly
relavent to my situation.

If it is warped, simply putting under great pressure (I have a few thousand
pounds of red bricks at hand), it's probably not pertinent *which* way it's
warped.

Placed on small square lumber and weighted, should give some good results.


You can press it flat all you want but unless you change either the
moisture content back to equilibrium at the time it was milled and
(presumably) flat or, if as noted previously, it was milled while not in
an equilibrium moisture content where it now is it will just return to
the present shape again.

If you can restrain it sufficiently, you _may_ be able to hold it in place.

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Excellent example is the cupping of hardwood floors, which "cup"
(concave side up) when wet from the underneath ... dry on the top, wet
on bottom ... one of the main reasons why a moisture barrier is always
used _beneath_ a hardwood floor.
[Swingman]


This doesn't hold water ;-) when speaking of this table top. The bottom is
not likely to be "soaked" in water but free to dry, much more so than the
top. The top is exposed to water (rain, spillage), whereas the underside has
little exposure to water except for the little that drips around the edges of
the table and which gravity will pull it off immediately.

The bottom side of the table top looks nearly pristine, whereas the top looks
like it's been through a war: the factory finish (polyurethane?) is still on
the underside of the wood but long since baked off the top (from sun
exposure).

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On 2/23/2012 11:26 AM, Paul Conners wrote:
Excellent example is the cupping of hardwood floors, which "cup"
(concave side up) when wet from the underneath ... dry on the top, wet
on bottom ... one of the main reasons why a moisture barrier is always
used _beneath_ a hardwood floor.
[Swingman]


This doesn't hold water ;-) when speaking of this table top. The bottom is
not likely to be "soaked" in water but free to dry, much more so than the
top. The top is exposed to water (rain, spillage), whereas the underside has
little exposure to water except for the little that drips around the edges of
the table and which gravity will pull it off immediately.

The bottom side of the table top looks nearly pristine, whereas the top looks
like it's been through a war: the factory finish (polyurethane?) is still on
the underside of the wood but long since baked off the top (from sun
exposure).


You obviously did not bother to read the very specific quote at the end
of my post that deals with "sun exposure". LOL

You're right that what you quote above does not apply to your table
....nor was it ever intended to.

What does indeed apply to your table is the description you used in your
original post ... the term "weathered".

You might want to go back and read the second "example" I used for the
effects of moisture on the dimensional stability of wood, as well as the
quote at the bottom which specifically deals with wood subjected to sun
and "weather".

If you did not accurately describe the condition of your table, then you
have no one to blame but yourself for misapplying the examples.

Just so there is no mistake how appropriate the quote was to your table
suffering "sun exposure" (sic), here it is again:

quote
Wood warmed by the sun experiences a virtual RH far below the ambient
RH. The surface dries faster than the rest of the lumber. This is why
cupping and checking often occur on decking boards; the top surface is
much drier than the rest of the board. Shrinkage of the top surface
commensurate with this dryness causes cupping and checking parallel to
the grain
/quote

It really does help to read an _entire_ post, not just those parts you
want to take exception to.

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