I have a pierce of 3/4 plywood, about 5'by2', currently the back of a
desk hutch. Once upon a time, it was a headboard, but it got cut down
when we "downsized" and 'tad-dah!" I had the back piece and the side
piece uprights.

But it was warped. In both directions.

Any suggestions for "straightening a sheet of plywood?

(I know, I could just find the "flattest" part and cut that out)

--
pyotr filipivich.
Discussing the decline in the US's tech edge, James Niccol once wrote
"It used to be that the USA was pretty good at producing stuff teenaged
boys could lose a finger or two playing with."

On 1/17/2023 13:31, pyotr filipivich wrote:
> I have a pierce of 3/4 plywood, about 5'by2', currently the back of a
> desk hutch. Once upon a time, it was a headboard, but it got cut down
> when we "downsized" and 'tad-dah!" I had the back piece and the side
> piece uprights.
>
> But it was warped. In both directions.
>
> Any suggestions for "straightening a sheet of plywood?
>
> (I know, I could just find the "flattest" part and cut that out)

Do you have anything heavy, such as a stack of drywall sheets? Last
time, I stacked about 20 panels of drywall on some warped plywood, and
when I came back to the house project a couple of weeks later, it
certainly made an improvement. I'm sure that a number of 80# bags of
concrete would do the trick, also.

Years ago, I know that they steamed wood to bend it into shapes for
intricate woodwork. I surely can't say that I've tried that method.

On 1/17/2023 1:31 PM, pyotr filipivich wrote:
> I have a pierce of 3/4 plywood, about 5'by2', currently the back of a
> desk hutch. Once upon a time, it was a headboard, but it got cut down
> when we "downsized" and 'tad-dah!" I had the back piece and the side
> piece uprights.
>
> But it was warped. In both directions.
>
> Any suggestions for "straightening a sheet of plywood?
>
> (I know, I could just find the "flattest" part and cut that out)
>

Probably if you soaked it in water for a while, and clamped it in an
appropriately size improvised vise (with 1 or perhaps even 2 pieces of
3/4" plywood on each side, and plenty of clamps (bolts might help too)),
and let it dry, then that would most likely flatten it out to a great deal.
However, I have no ideal "how long" this fix would last. If you have
high humidity, it might not last long. To be honest, I would probably
replace the piece, and never look back! You might experience better
results with Baltic Birch plywood ($$)--I believe it is usually sold in
5'x5' sheets. But I have no experience or expertise trying to what you
are trying to do. Good luck! A before and after picture would be
interesting.

P.S. The "floor" of the cabinet under my kitchen sink has similar,
possibly even more extreme, warp-age. But since She caused the problem
by negligence, and since it is usually out of view, it is not close to
the top of my list of "home projects for me". Someday I may replace
it--though I anticipate that I will need to replace it in two pieces
instead of just one (I'll almost surely have to remove it that way
too!). Now, please don't feel bad that you reminded me about this! ; )

On 1/17/2023 3:29 PM, Michael Trew wrote:
> On 1/17/2023 13:31, pyotr filipivich wrote:
>> I have a pierce of 3/4 plywood, about 5'by2', currently the back of a
>> desk hutch.  Once upon a time, it was a headboard, but it got cut down
>> when we "downsized" and 'tad-dah!" I had the back piece and the side
>> piece uprights.
>>
>> But it was warped.  In both directions.
>>
>> Any suggestions for "straightening a sheet of plywood?
>>
>> (I know, I could just find the "flattest" part and cut that out)
>
> Do you have anything heavy, such as a stack of drywall sheets?  Last
> time, I stacked about 20 panels of drywall on some warped plywood, and
> when I came back to the house project a couple of weeks later, it
> certainly made an improvement.  I'm sure that a number of 80# bags of
> concrete would do the trick, also.
>
> Years ago, I know that they steamed wood to bend it into shapes for
> intricate woodwork.  I surely can't say that I've tried that method.

They still do that to shape wood for things like acoustic guitar sides
(think about how it needs to curve like an "S").

Michael Trew <michael.trew@att.net> on Tue, 17 Jan 2023 15:29:12 -0500
typed in rec.woodworking the following:
>On 1/17/2023 13:31, pyotr filipivich wrote:
>> I have a pierce of 3/4 plywood, about 5'by2', currently the back of a
>> desk hutch. Once upon a time, it was a headboard, but it got cut down
>> when we "downsized" and 'tad-dah!" I had the back piece and the side
>> piece uprights.
>>
>> But it was warped. In both directions.
>>
>> Any suggestions for "straightening a sheet of plywood?
>>
>> (I know, I could just find the "flattest" part and cut that out)
>
>Do you have anything heavy, such as a stack of drywall sheets? Last
>time, I stacked about 20 panels of drywall on some warped plywood, and
>when I came back to the house project a couple of weeks later, it
>certainly made an improvement. I'm sure that a number of 80# bags of
>concrete would do the trick, also.
>
>Years ago, I know that they steamed wood to bend it into shapes for
>intricate woodwork. I surely can't say that I've tried that method.

I have affirmed who does that. Not sure he has a setup which can
"scale" B-)
--
pyotr filipivich
"With Age comes Wisdom. Although far too often, Age travels alone."

Bill <nonegiven@att.net> on Tue, 17 Jan 2023 15:49:26 -0500 typed in
rec.woodworking the following:
>On 1/17/2023 1:31 PM, pyotr filipivich wrote:
>> I have a pierce of 3/4 plywood, about 5'by2', currently the back of a
>> desk hutch. Once upon a time, it was a headboard, but it got cut down
>> when we "downsized" and 'tad-dah!" I had the back piece and the side
>> piece uprights.
>>
>> But it was warped. In both directions.
>>
>> Any suggestions for "straightening a sheet of plywood?
>>
>> (I know, I could just find the "flattest" part and cut that out)
>>
>
>Probably if you soaked it in water for a while, and clamped it in an
>appropriately size improvised vise (with 1 or perhaps even 2 pieces of
>3/4" plywood on each side, and plenty of clamps (bolts might help too)),
>and let it dry, then that would most likely flatten it out to a great deal.
>However, I have no ideal "how long" this fix would last. If you have
>high humidity, it might not last long. To be honest, I would probably
>replace the piece, and never look back! You might experience better
>results with Baltic Birch plywood ($$)--I believe it is usually sold in
>5'x5' sheets.

Hmmm, I think I'll just look into a) is there a 32" stretch which
is "mostly flat"? or b) what can I find in "fall down" bin at
BigBoxInc.

>But I have no experience or expertise trying to what you
>are trying to do. Good luck! A before and after picture would be
>interesting.
>
>P.S. The "floor" of the cabinet under my kitchen sink has similar,
>possibly even more extreme, warp-age. But since She caused the problem
>by negligence, and since it is usually out of view, it is not close to
>the top of my list of "home projects for me". Someday I may replace
>it--though I anticipate that I will need to replace it in two pieces
>instead of just one (I'll almost surely have to remove it that way
>too!). Now, please don't feel bad that you reminded me about this! ; )
--
pyotr filipivich
"With Age comes Wisdom. Although far too often, Age travels alone."

On 1/17/2023 5:30 PM, pyotr filipivich wrote:
> Bill <nonegiven@att.net> on Tue, 17 Jan 2023 15:49:26 -0500 typed in
> rec.woodworking the following:
>> On 1/17/2023 1:31 PM, pyotr filipivich wrote:
>>> I have a pierce of 3/4 plywood, about 5'by2', currently the back of a
>>> desk hutch. Once upon a time, it was a headboard, but it got cut down
>>> when we "downsized" and 'tad-dah!" I had the back piece and the side
>>> piece uprights.
>>>
>>> But it was warped. In both directions.
>>>
>>> Any suggestions for "straightening a sheet of plywood?
>>>
>>> (I know, I could just find the "flattest" part and cut that out)
>>>
>>
>> Probably if you soaked it in water for a while, and clamped it in an
>> appropriately size improvised vise (with 1 or perhaps even 2 pieces of
>> 3/4" plywood on each side, and plenty of clamps (bolts might help too)),
>> and let it dry, then that would most likely flatten it out to a great deal.
>> However, I have no ideal "how long" this fix would last. If you have
>> high humidity, it might not last long. To be honest, I would probably
>> replace the piece, and never look back! You might experience better
>> results with Baltic Birch plywood ($$)--I believe it is usually sold in
>> 5'x5' sheets.
>
> Hmmm, I think I'll just look into a) is there a 32" stretch which
> is "mostly flat"? or b) what can I find in "fall down" bin at
> BigBoxInc.

Don't hesitate to borrow a level to use as a straight-edge from another
aisle of the store. Good luck with your project!

On Tuesday, January 17, 2023 at 8:21:31 PM UTC-5, Bill wrote:
> On 1/17/2023 5:30 PM, pyotr filipivich wrote:
> > Bill <none...@att.net> on Tue, 17 Jan 2023 15:49:26 -0500 typed in
> > rec.woodworking the following:
> >> On 1/17/2023 1:31 PM, pyotr filipivich wrote:
> >>> I have a pierce of 3/4 plywood, about 5'by2', currently the back of a
> >>> desk hutch. Once upon a time, it was a headboard, but it got cut down
> >>> when we "downsized" and 'tad-dah!" I had the back piece and the side
> >>> piece uprights.
> >>>
> >>> But it was warped. In both directions.
> >>>
> >>> Any suggestions for "straightening a sheet of plywood?
> >>>
> >>> (I know, I could just find the "flattest" part and cut that out)
> >>>
> >>
> >> Probably if you soaked it in water for a while, and clamped it in an
> >> appropriately size improvised vise (with 1 or perhaps even 2 pieces of
> >> 3/4" plywood on each side, and plenty of clamps (bolts might help too)),
> >> and let it dry, then that would most likely flatten it out to a great deal.
> >> However, I have no ideal "how long" this fix would last. If you have
> >> high humidity, it might not last long. To be honest, I would probably
> >> replace the piece, and never look back! You might experience better
> >> results with Baltic Birch plywood ($$)--I believe it is usually sold in
> >> 5'x5' sheets.
> >
> > Hmmm, I think I'll just look into a) is there a 32" stretch which
> > is "mostly flat"? or b) what can I find in "fall down" bin at
> > BigBoxInc.
> Don't hesitate to borrow a level to use as a straight-edge from another
> aisle of the store. Good luck with your project!

Warped plywood is often caused by unequal moisture content across both sides. See if there is a grade stamp on the back/bad side of the plywood. If you see something like ABX or BCX or CDX, or the word Exterior appears, it has exterior glue and can be dampened. If it has a grade stamp indicating Interior use ignore the dampening directions here and try the flipping part. As this started life in furniture there is a good chance it doesn't have exterior glue...

If you dampen the concave side, and place that side down on a flat surface, it may straighten itself out in a few days. Putting a blue tarp or plastic sheeting under it will help retain the moisture (keep the "floor" from sucking moisture out of the plywood). Sometimes just flipping a sheet over and exposing "the other side" to the same conditions as the "first side" is all it takes to equalize the moisture content. Note that 3/4" will generally take a bit longer to normalize than 1/2".

Bill <nonegiven@att.net> on Tue, 17 Jan 2023 20:21:24 -0500 typed in
rec.woodworking the following:
>
>> Hmmm, I think I'll just look into a) is there a 32" stretch which
>> is "mostly flat"? or b) what can I find in "fall down" bin at
>> BigBoxInc.
>
>Don't hesitate to borrow a level to use as a straight-edge from another
>aisle of the store. Good luck with your project!

For what I want to do "eye ball" will do.
--
pyotr filipivich
"With Age comes Wisdom. Although far too often, Age travels alone."

John Grossbohlin <grossboj@gmail.com> on Tue, 17 Jan 2023 18:20:40
-0800 (PST) typed in rec.woodworking the following:
>> > Hmmm, I think I'll just look into a) is there a 32" stretch which
>> > is "mostly flat"? or b) what can I find in "fall down" bin at
>> > BigBoxInc.
>> Don't hesitate to borrow a level to use as a straight-edge from another
>> aisle of the store. Good luck with your project!
>
>Warped plywood is often caused by unequal moisture content across both sides. See if there is a grade stamp on the back/bad side of the plywood. If you see something like ABX or BCX or CDX, or the word Exterior appears, it has exterior glue and can be dampened. If it has a grade stamp indicating Interior use ignore the dampening directions here and try the flipping part. As this started life in furniture there is a good chance it doesn't have exterior glue...

I'm not sure where it "started" life. This was part of a
collection of "obtanium" (Things found which might be good for
something some day.)
>
>If you dampen the concave side, and place that side down on a flat surface, it may straighten itself out in a few days. Putting a blue tarp or plastic sheeting under it will help retain the moisture (keep the "floor" from sucking moisture out of the plywood). Sometimes just flipping a sheet over and exposing "the other side" to the same conditions as the "first side" is all it takes to equalize the moisture content. Note that 3/4" will generally take a bit longer to normalize than 1/2".

The concave side had a really thin piece of "very nice wood" glued
to it to make the plywood "look nice" on the side we would see. I
have pondered if that might have been a problem, but "Nope it would
have warped it the other way.
Now I am wondering if it might have absorbed moisture on that
side? If I leave the unfinished side facing the window, will it dry
out enough? Is that likely to happen in Seattle, in winter?
--
pyotr filipivich
"With Age comes Wisdom. Although far too often, Age travels alone."

On Tuesday, January 17, 2023 at 10:43:02 PM UTC-5, pyotr filipivich wrote:
> John Grossbohlin <gros...@gmail.com> on Tue, 17 Jan 2023 18:20:40

> >If you dampen the concave side, and place that side down on a flat surface, it may straighten itself out in a few days. Putting a blue tarp or plastic sheeting under it will help retain the moisture (keep the "floor" from sucking moisture out of the plywood). Sometimes just flipping a sheet over and exposing "the other side" to the same conditions as the "first side" is all it takes to equalize the moisture content. Note that 3/4" will generally take a bit longer to normalize than 1/2".
> The concave side had a really thin piece of "very nice wood" glued
> to it to make the plywood "look nice" on the side we would see. I
> have pondered if that might have been a problem, but "Nope it would
> have warped it the other way.
> Now I am wondering if it might have absorbed moisture on that
> side? If I leave the unfinished side facing the window, will it dry
> out enough? Is that likely to happen in Seattle, in winter?

At this point I'd try it and see what happens!

John Grossbohlin <grossboj@gmail.com> on Wed, 18 Jan 2023 05:54:01
-0800 (PST) typed in rec.woodworking the following:
>On Tuesday, January 17, 2023 at 10:43:02 PM UTC-5, pyotr filipivich wrote:
>> John Grossbohlin <gros...@gmail.com> on Tue, 17 Jan 2023 18:20:40
>
>> >If you dampen the concave side, and place that side down on a flat surface, it may straighten itself out in a few days. Putting a blue tarp or plastic sheeting under it will help retain the moisture (keep the "floor" from sucking moisture out of the plywood). Sometimes just flipping a sheet over and exposing "the other side" to the same conditions as the "first side" is all it takes to equalize the moisture content. Note that 3/4" will generally take a bit longer to normalize than 1/2".
>> The concave side had a really thin piece of "very nice wood" glued
>> to it to make the plywood "look nice" on the side we would see. I
>> have pondered if that might have been a problem, but "Nope it would
>> have warped it the other way.
>> Now I am wondering if it might have absorbed moisture on that
>> side? If I leave the unfinished side facing the window, will it dry
>> out enough? Is that likely to happen in Seattle, in winter?
>
>At this point I'd try it and see what happens!

Easiest option. Now all I have to do is wait for the sun to
shine.
--
pyotr filipivich
"With Age comes Wisdom. Although far too often, Age travels alone."

On Tuesday, January 17, 2023 at 1:31:06 PM UTC-5, pyotr filipivich wrote:
> I have a pierce of 3/4 plywood, about 5'by2', currently the back of a
> desk hutch. Once upon a time, it was a headboard, but it got cut down
> when we "downsized" and 'tad-dah!" I had the back piece and the side
> piece uprights.
>
> But it was warped. In both directions.
>
> Any suggestions for "straightening a sheet of plywood?
>
> (I know, I could just find the "flattest" part and cut that out)
>

5' x 2'?

Go to a home center and get a full sized sheet.

Then you'll have an 8' x 4' sheet of warped plywood. ;-)

On Tuesday, January 17, 2023 at 10:43:02 PM UTC-5, pyotr filipivich wrote:
> John Grossbohlin <gros...@gmail.com> on Tue, 17 Jan 2023 18:20:40
> -0800 (PST) typed in rec.woodworking the following:
> >> > Hmmm, I think I'll just look into a) is there a 32" stretch which
> >> > is "mostly flat"? or b) what can I find in "fall down" bin at
> >> > BigBoxInc.
> >> Don't hesitate to borrow a level to use as a straight-edge from another
> >> aisle of the store. Good luck with your project!
> >
> >Warped plywood is often caused by unequal moisture content across both sides. See if there is a grade stamp on the back/bad side of the plywood. If you see something like ABX or BCX or CDX, or the word Exterior appears, it has exterior glue and can be dampened. If it has a grade stamp indicating Interior use ignore the dampening directions here and try the flipping part.. As this started life in furniture there is a good chance it doesn't have exterior glue...
> I'm not sure where it "started" life. This was part of a
> collection of "obtanium" (Things found which might be good for
> something some day.)
> >

You only have to see 1 side right?

Is there any angle iron or similar in your obtanium vault?

Mount the plywood on something straight and stiff that would
force it back to flat.

Maybe use some decorative bolts or other means to
make the mounting hardware seem like a design feature.

DerbyDad03 <teamarrows@eznet.net> on Wed, 18 Jan 2023 15:16:32 -0800
(PST) typed in rec.woodworking the following:
>On Tuesday, January 17, 2023 at 1:31:06 PM UTC-5, pyotr filipivich wrote:
>> I have a pierce of 3/4 plywood, about 5'by2', currently the back of a
>> desk hutch. Once upon a time, it was a headboard, but it got cut down
>> when we "downsized" and 'tad-dah!" I had the back piece and the side
>> piece uprights.
>>
>> But it was warped. In both directions.
>>
>> Any suggestions for "straightening a sheet of plywood?
>>
>> (I know, I could just find the "flattest" part and cut that out)
>>
>
>5' x 2'?
>
>Go to a home center and get a full sized sheet.

Have you seen the price of plywood??? B-) That's why I'm reusing
it.
>
>Then you'll have an 8' x 4' sheet of warped plywood. ;-)

Snerk.

Reminded of the cartoon of the two welders at a Modern Sculpture
Exhibit. "Sure it's Art. But can you really say that it is welding?"
--
pyotr filipivich
"With Age comes Wisdom. Although far too often, Age travels alone."

DerbyDad03 <teamarrows@eznet.net> on Wed, 18 Jan 2023 15:23:11 -0800
(PST) typed in rec.woodworking the following:
>On Tuesday, January 17, 2023 at 10:43:02 PM UTC-5, pyotr filipivich wrote:
>> John Grossbohlin <gros...@gmail.com> on Tue, 17 Jan 2023 18:20:40
>> -0800 (PST) typed in rec.woodworking the following:
>> >> > Hmmm, I think I'll just look into a) is there a 32" stretch which
>> >> > is "mostly flat"? or b) what can I find in "fall down" bin at
>> >> > BigBoxInc.
>> >> Don't hesitate to borrow a level to use as a straight-edge from another
>> >> aisle of the store. Good luck with your project!
>> >
>> >Warped plywood is often caused by unequal moisture content across both sides. See if there is a grade stamp on the back/bad side of the plywood. If you see something like ABX or BCX or CDX, or the word Exterior appears, it has exterior glue and can be dampened. If it has a grade stamp indicating Interior use ignore the dampening directions here and try the flipping part. As this started life in furniture there is a good chance it doesn't have exterior glue...
>> I'm not sure where it "started" life. This was part of a
>> collection of "obtanium" (Things found which might be good for
>> something some day.)
>
>You only have to see 1 side right?

At best.
>
>Is there any angle iron or similar in your obtanium vault?

Lemmee see ... I know I have some channel AL from some place.
>
>Mount the plywood on something straight and stiff that would
>force it back to flat.
>
>Maybe use some decorative bolts or other means to
>make the mounting hardware seem like a design feature.

Or, I could just work the warp into the design, then make
allusions to the extraordinary effort it took to get just the right
amount of curve into the wood for this effect.
"It's not a bug, it's a feature!"
--
pyotr filipivich
"With Age comes Wisdom. Although far too often, Age travels alone."

On 1/17/2023 2:49 PM, Bill wrote:
> On 1/17/2023 1:31 PM, pyotr filipivich wrote:
>> I have a pierce of 3/4 plywood, about 5'by2', currently the back of a
>> desk hutch.  Once upon a time, it was a headboard, but it got cut down
>> when we "downsized" and 'tad-dah!" I had the back piece and the side
>> piece uprights.
>>
>> But it was warped.  In both directions.
>>
>> Any suggestions for "straightening a sheet of plywood?
>>
>> (I know, I could just find the "flattest" part and cut that out)
>>
>
> Probably if you soaked it in water for a while,

NOT A GOOD IDEA

and clamped it in an
> appropriately size improvised vise (with 1 or perhaps even 2 pieces of
> 3/4" plywood on each side, and plenty of clamps (bolts might help too)),
> and let it dry, then that would most likely flatten it out to a great deal.
> However, I have no ideal "how long" this fix would last. If you have
> high humidity, it might not last long.  To be honest, I would probably
> replace the piece, and never look back! You might experience better
> results with Baltic Birch plywood ($$)--I believe it is usually sold in
> 5'x5' sheets.   But I have no experience or expertise trying to what you
> are trying to do.  Good luck!  A before and after picture would be
> interesting.
>
> P.S. The "floor" of the cabinet under my kitchen sink has similar,
> possibly even more extreme, warp-age. But since She caused the problem
> by negligence, and since it is usually out of view, it is not close to
> the top of my list of "home projects for me". Someday I may replace
> it--though I anticipate that I will need to replace it in two pieces
> instead of just one (I'll almost surely have to remove it that way
> too!). Now, please don't feel bad that you reminded me about this!  ; )

On Wed, 18 Jan 2023 21:26:45 -0800, pyotr filipivich
<phamp@mindspring.com> wrote:

>DerbyDad03 <teamarrows@eznet.net> on Wed, 18 Jan 2023 15:16:32 -0800
>(PST) typed in rec.woodworking the following:
>>On Tuesday, January 17, 2023 at 1:31:06 PM UTC-5, pyotr filipivich wrote:
>>> I have a pierce of 3/4 plywood, about 5'by2', currently the back of a
>>> desk hutch. Once upon a time, it was a headboard, but it got cut down
>>> when we "downsized" and 'tad-dah!" I had the back piece and the side
>>> piece uprights.
>>>
>>> But it was warped. In both directions.
>>>
>>> Any suggestions for "straightening a sheet of plywood?
>>>
>>> (I know, I could just find the "flattest" part and cut that out)
>>>
>>
>>5' x 2'?
>>
>>Go to a home center and get a full sized sheet.
>
> Have you seen the price of plywood??? B-) That's why I'm reusing
>it.
>>
>>Then you'll have an 8' x 4' sheet of warped plywood. ;-)
>
> Snerk.
>
> Reminded of the cartoon of the two welders at a Modern Sculpture
>Exhibit. "Sure it's Art. But can you really say that it is welding?"

Is this either?
<https://www.axios.com/local/boston/2023/01/13/martin-luther-king-boston-common-memorial-hug>

On 1/19/2023 11:47 AM, Leon wrote:
> On 1/17/2023 2:49 PM, Bill wrote:
>> On 1/17/2023 1:31 PM, pyotr filipivich wrote:
>>> I have a pierce of 3/4 plywood, about 5'by2', currently the back of a
>>> desk hutch.  Once upon a time, it was a headboard, but it got cut down
>>> when we "downsized" and 'tad-dah!" I had the back piece and the side
>>> piece uprights.
>>>
>>> But it was warped.  In both directions.
>>>
>>> Any suggestions for "straightening a sheet of plywood?
>>>
>>> (I know, I could just find the "flattest" part and cut that out)
>>>
>>
>> Probably if you soaked it in water for a while,
>
> NOT A GOOD IDEA

You wouldn't get it wet? My understanding is that water makes wood more
flexible. I know there is some glue in plywood, but I didn't say to
soak it until it fell apart! : ) I was the one who also advocated
simply replacing it--the wet-flex-fix is a last ditch effort!

>
>
>
>
> and clamped it in an
>> appropriately size improvised vise (with 1 or perhaps even 2 pieces of
>> 3/4" plywood on each side, and plenty of clamps (bolts might help
>> too)), and let it dry, then that would most likely flatten it out to a
>> great deal.
>> However, I have no ideal "how long" this fix would last. If you have
>> high humidity, it might not last long.  To be honest, I would probably
>> replace the piece, and never look back! You might experience better
>> results with Baltic Birch plywood ($$)--I believe it is usually sold
>> in 5'x5' sheets.   But I have no experience or expertise trying to
>> what you are trying to do.  Good luck!  A before and after picture
>> would be interesting.
>>
>> P.S. The "floor" of the cabinet under my kitchen sink has similar,
>> possibly even more extreme, warp-age. But since She caused the problem
>> by negligence, and since it is usually out of view, it is not close to
>> the top of my list of "home projects for me". Someday I may replace
>> it--though I anticipate that I will need to replace it in two pieces
>> instead of just one (I'll almost surely have to remove it that way
>> too!). Now, please don't feel bad that you reminded me about this!  ; )
>

On 1/19/2023 11:49 PM, Bill wrote:
> On 1/19/2023 11:47 AM, Leon wrote:
>> On 1/17/2023 2:49 PM, Bill wrote:
>>> On 1/17/2023 1:31 PM, pyotr filipivich wrote:
>>>> I have a pierce of 3/4 plywood, about 5'by2', currently the back of a
>>>> desk hutch.  Once upon a time, it was a headboard, but it got cut down
>>>> when we "downsized" and 'tad-dah!" I had the back piece and the side
>>>> piece uprights.
>>>>
>>>> But it was warped.  In both directions.
>>>>
>>>> Any suggestions for "straightening a sheet of plywood?
>>>>
>>>> (I know, I could just find the "flattest" part and cut that out)
>>>>
>>>
>>> Probably if you soaked it in water for a while,
>>
>> NOT A GOOD IDEA
>
> You wouldn't get it wet?  My understanding is that water makes wood more
> flexible.  I know there is some glue in plywood, but I didn't say to
> soak it until it fell apart!  : )  I was the one who also advocated
> simply replacing it--the wet-flex-fix is a last ditch effort!

But you did say soak it "in" water, and who is to say how much is enough
and how much is too much If not in a mold I would fear de-lamination.
AND the OP said that it was once a headboard so it likely had a nice
veneer with a finish on it. Most if not all bending I have seen was
with steam and molds on unfinished plywood/wood.

Leon <lcb11211@swbelldotnet> on Thu, 19 Jan 2023 10:47:48 -0600 typed
in rec.woodworking the following:
>On 1/17/2023 2:49 PM, Bill wrote:
>> On 1/17/2023 1:31 PM, pyotr filipivich wrote:
>>> I have a pierce of 3/4 plywood, about 5'by2', currently the back of a
>>> desk hutch.  Once upon a time, it was a headboard, but it got cut down
>>> when we "downsized" and 'tad-dah!" I had the back piece and the side
>>> piece uprights.
>>>
>>> But it was warped.  In both directions.
>>>
>>> Any suggestions for "straightening a sheet of plywood?
>>>
>>> (I know, I could just find the "flattest" part and cut that out)
>>>
>>
>> Probably if you soaked it in water for a while,
>
>NOT A GOOD IDEA

I thought the same - don't have a bath tub.

Besides, might be simpler to just get a couple more heat lamps and
dry the convex side.
--
pyotr filipivich
"With Age comes Wisdom. Although far too often, Age travels alone."

krw@notreal.com on Thu, 19 Jan 2023 22:18:44 -0500 typed in
rec.woodworking the following:
>On Wed, 18 Jan 2023 21:26:45 -0800, pyotr filipivich
><phamp@mindspring.com> wrote:
>
>>DerbyDad03 <teamarrows@eznet.net> on Wed, 18 Jan 2023 15:16:32 -0800
>>(PST) typed in rec.woodworking the following:
>>>On Tuesday, January 17, 2023 at 1:31:06 PM UTC-5, pyotr filipivich wrote:
>>>> I have a pierce of 3/4 plywood, about 5'by2', currently the back of a
>>>> desk hutch. Once upon a time, it was a headboard, but it got cut down
>>>> when we "downsized" and 'tad-dah!" I had the back piece and the side
>>>> piece uprights.
>>>>
>>>> But it was warped. In both directions.
>>>>
>>>> Any suggestions for "straightening a sheet of plywood?
>>>>
>>>> (I know, I could just find the "flattest" part and cut that out)
>>>>
>>>
>>>5' x 2'?
>>>
>>>Go to a home center and get a full sized sheet.
>>
>> Have you seen the price of plywood??? B-) That's why I'm reusing
>>it.
>>>
>>>Then you'll have an 8' x 4' sheet of warped plywood. ;-)
>>
>> Snerk.
>>
>> Reminded of the cartoon of the two welders at a Modern Sculpture
>>Exhibit. "Sure it's Art. But can you really say that it is welding?"
>
>Is this either?
><https://www.axios.com/local/boston/2023/01/13/martin-luther-king-boston-common-memorial-hug>

Ah, no.
--
pyotr filipivich
"With Age comes Wisdom. Although far too often, Age travels alone."

On 1/20/2023 11:58 AM, Leon wrote:
> On 1/19/2023 11:49 PM, Bill wrote:
>> On 1/19/2023 11:47 AM, Leon wrote:
>>> On 1/17/2023 2:49 PM, Bill wrote:
>>>> On 1/17/2023 1:31 PM, pyotr filipivich wrote:
>>>>> I have a pierce of 3/4 plywood, about 5'by2', currently the back of a
>>>>> desk hutch.  Once upon a time, it was a headboard, but it got cut down
>>>>> when we "downsized" and 'tad-dah!" I had the back piece and the side
>>>>> piece uprights.
>>>>>
>>>>> But it was warped.  In both directions.
>>>>>
>>>>> Any suggestions for "straightening a sheet of plywood?
>>>>>
>>>>> (I know, I could just find the "flattest" part and cut that out)
>>>>>
>>>>
>>>> Probably if you soaked it in water for a while,
>>>
>>> NOT A GOOD IDEA
>>
>> You wouldn't get it wet?  My understanding is that water makes wood
>> more flexible.  I know there is some glue in plywood, but I didn't say
>> to soak it until it fell apart!  : )  I was the one who also advocated
>> simply replacing it--the wet-flex-fix is a last ditch effort!
>
> But you did say soak it "in" water, and who is to say how much is enough
> and how much is too much

I subscribe to the motto, "Sometimes you have to be willing to break it
in order to fix it". And sometimes I break it, but fortunately most of
the time I don't. : )

On 1/20/2023 8:29 PM, Bill wrote:
> On 1/20/2023 11:58 AM, Leon wrote:
>> On 1/19/2023 11:49 PM, Bill wrote:
>>> On 1/19/2023 11:47 AM, Leon wrote:
>>>> On 1/17/2023 2:49 PM, Bill wrote:
>>>>> On 1/17/2023 1:31 PM, pyotr filipivich wrote:
>>>>>> I have a pierce of 3/4 plywood, about 5'by2', currently the back of a
>>>>>> desk hutch.  Once upon a time, it was a headboard, but it got cut
>>>>>> down
>>>>>> when we "downsized" and 'tad-dah!" I had the back piece and the side
>>>>>> piece uprights.
>>>>>>
>>>>>> But it was warped.  In both directions.
>>>>>>
>>>>>> Any suggestions for "straightening a sheet of plywood?
>>>>>>
>>>>>> (I know, I could just find the "flattest" part and cut that out)
>>>>>>
>>>>>
>>>>> Probably if you soaked it in water for a while,
>>>>
>>>> NOT A GOOD IDEA
>>>
>>> You wouldn't get it wet?  My understanding is that water makes wood
>>> more flexible.  I know there is some glue in plywood, but I didn't
>>> say to soak it until it fell apart!  : )  I was the one who also
>>> advocated simply replacing it--the wet-flex-fix is a last ditch effort!
>>
>> But you did say soak it "in" water, and who is to say how much is
>> enough and how much is too much
>
> I subscribe to the motto, "Sometimes you have to be willing to break it
> in order to fix it". And sometimes I break it, but fortunately most of
> the time I don't. : )

Thumbs up!