Clamp Pressure Damaged Cherry ???

[Rob Will]

Has anybody seen clamp pressure stain cherry lumber?
I was using some scrap cherry to add end caps to a shop cabinet.
The parts were glued and finish nailed to the ends of the cabinet. Several clamps were applied to make everything pull down tight.

After sitting under clamp pressure overnight, the cherry shows signs of staining. (???)

It should be noted that I did not apply excessive pressure and the clamps had cushioned surfaces. In fact, on one end I used a piece of 3/4" birch plywood against the cherry to help spread clamping pressure.

Here's the weird part....
The piece of birch plywood seems to have absorbed the stained color. This occured everywhere there was clamp pressure.

What is going on here? Does cherry have some sort of oil in it?
This particular cabinet is to be painted so this is not a problem - this time. What happened?

TIA,
Rob

[Mike Schmalzer]

I have seen this many times with cherry but not with all cherry. I am not sure that it is oils or something else. A bit of sanding and some steam usually gets rid of it. I always assume that it will happen with cherry so I always use rubber covers on the clamps and make sure my joinery is perfect to eliminate excessive clamping. Hope that helps.

Mike

[Dewey Torres]

I usually just avoid Cherry...Not kidding here! I like the way Jatoba looks better anyway. Why does cheery have to be such a bear to use??? I have seen cats less finicky.

Dewey

[Rick Thom]

Rob is it possible that the pads on your clamps weren't perfectly clean before you used them?
I was finding this with mine as well and the source was a bit of BLO or some such thing on the pads from a previous job so I pulled them all off and gave them a thorough cleaning and scraping of old glue etc. Problem solved for now. I do believe that cherry shows staining more than most wood species.

[Rob Will]

Rob is it possible that the pads on your clamps weren't perfectly clean before you used them?
I was finding this with mine as well and the source was a bit of BLO or some such thing on the pads from a previous job so I pulled them all off and gave them a thorough cleaning and scraping of old glue etc. Problem solved for now. I do believe that cherry shows staining more than most wood species.

Hi Rick,
Actually the clamps were new and had the plastic pads attached.
In my first pic, that is where the pads made direct contact with the cherry (two stains side by side).

In the second and third pics, the clamps were not in contact with the cherry at all. The plywood strip was against the cherry acting as a pad. Note that the plywood absorbed the stain everywhere there was clamp pressure. The cherry shows an identical pattern. There is no staining where the clamps were pressing against the opposite side of the plywood.

Thanks,
Rob

[Brian Kerley]

Rob, in the latest FWW, they had someone write in with this problem. Basically, under pressure you are forcing some of the oils out of plastic/rubber clamp pads into the wood. The letter had mentioned something about Jorgensen clamps having this problem in particular.

[Rob Will]

Rob, in the latest FWW, they had someone write in with this problem. Basically, under pressure you are forcing some of the oils out of plastic/rubber clamp pads into the wood. The letter had mentioned something about Jorgensen clamps having this problem in particular.

Thanks Brian,
Yes, I was using Jorgensen clamps but one end of my glue up had the plywood pad in-between.

I'm wondering what a bit of Naptha would do to the stain,
(if it is indeed oil)

I just went out to the shop and set up a test with several different clamps on a similar cherry board.
One of the Jorgensen clamps has brand new plastic pads right out of the package.
Let's leave it under pressure for a couple of days and see if we can make this happen again.

Rob

[Norman Pyles]

Rob, my Jorgensen clamp pads do the same thing, on oak. Been thinking about taking them off, and using the clamps without the pads.

[Barry Nelson]

I think that some types of vynil sweat, may be thats what happened to yours:confused:

[Sean Kinn]

Just incase you needed another vote...yes it's the orange pads on the Jorgy's. Mine do it too. Per the FWW article:

"If you need to remove clamp-pad stains from existing workpieces, lightly sand the affected areas or wipe them with mineral spirits or naphtha. Either one should do the trick."

P.S. Sanding has worked for me, but I was aware of this problem ahead of time and used wooden pads under the clamp 99% of the time.

[Todd Bin]

I had the same problem with some African Mahogany. I rubbed a little Naptha and sanded a little. Some of the "spots" would not come out but I wasn't too worried. I applied a Tung oil finish to the project and the spots disappeared completely. I would have been sweating it if I was going to choose some other kind of finish.

[Tom Esh]

As others have noted, it's probably the pad compound or some other residual oil on the pads. I use wood clamp pads for that reason. If you have one of those otherwise useless twisty borg 2x4s lying around you can whip up a few of these in no time...

[David DeCristoforo]

Take those little plastic pads off the clamp jaws and drop them into the nearest trash can. Use some wood pads instead. You can either drill them out so they ride on the pipe as in Tom's pic or just stick them onto the clamp jaws with a spot of hot melt glue. Or, if you have enough arms, just hold them in place and tighten up the clamps. In any case, the plastic pads are too "squishy" for my taste. (Oh, what? You're not supposed to eat them? Now you tell me.....)

[Lee Schierer]

Hi Rick,
Actually the clamps were new and had the plastic pads attached.


Now that's your problem. The plastic pads, particularly when new tend to stain wood. The plasitsizer in them leaches out under pressure. Clean the area with Lacquer thinner. I recommend not using them or placing a sacrificial piece of wood between them and the good wood.

[john bateman]

The guy has stated that the marks appear even when using a piece of plywood between the clamp pads and the cherry....yet all these replies keep telling him it's the vinyl pads. It can't be!
Look at the picture. The marks are on both pieces of wood which were facing each other.
http://sawmillcreek.org/attachment.php?attachmentid=86898&d=1208748587

[David Peters]

Or, if you have enough arms, just hold them in place and tighten up the clamps.

What I wouldn't give for an extra pair of arms at glue-up time!

I recently went through a rather stressful glue-up on a Cherry piece and after finally getting everything together and clamped properly, I checked the stopwatch and it was more than 8 minutes from the time I started. Let's hope everything stays together once the clamps come off.

Maybe it's time for me to start looking at some glues with extended open time....

[Paul Simmel]

The guy has stated that the marks appear even when using a piece of plywood between the clamp pads and the cherry....yet all these replies keep telling him it's the vinyl pads. It can't be!
Look at the picture. The marks are on both pieces of wood which were facing each other.
http://sawmillcreek.org/attachment.php?attachmentid=86898&d=1208748587

Yes. The OP was very clear on the issue.

Since the stain was absorbed by the ply in the exact same areas where the clamping pressure was applied, I'd be interested as heck to see why this cherry bleeds like that.

[Chris Padilla]

Maybe it's time for me to start looking at some glues with extended open time....

Epoxy and Plastic Resin glue come to mind. There is nothing more stressful than a glue-up with glue setting faster than you like!

[Kent Novick]

The guy has stated that the marks appear even when using a piece of plywood between the clamp pads and the cherry....yet all these replies keep telling him it's the vinyl pads. It can't be!
Look at the picture. The marks are on both pieces of wood which were facing each other.
http://sawmillcreek.org/attachment.php?attachmentid=86898&d=1208748587

The other staining is definitely from the pads. Having it bleed all the way through the ply is unlikely, however... Is it possible that the piece of ply had been used as a caul before this glue-up? I had the same issue when using a piece of mdf for a caul, and got the staining. Without thinking, I grabbed it for another glue-up and just put the clamp-stained side facing the wood. The stain transferred from the mdf to the wood, just as thought the clamp was on the wood directly.

[Paul Simmel]

Kent,

Check out the second and third pic's.

[Kent Novick]

Kent,

Check out the second and third pic's.


That's what I'm referring to. Having the stain bleed through the plywood from the pads would be weird, but it could transfer if the plywood had been used before and stained by clamping, and the stained part had been placed against the cherry. I've had it happen.

[Stephen Edwards]

As others have noted, it's probably the pad compound or some other residual oil on the pads. I use wood clamp pads for that reason. If you have one of those otherwise useless twisty borg 2x4s lying around you can whip up a few of these in no time...

What a great idea! Thanks for the photo. That looks much easier than constantly having to position the piece of wood between the glue up stock and the clamp. Why haven't I thought of that already?!

[Tom Esh]

What a great idea! Thanks for the photo. That looks much easier than constantly having to position the piece of wood between the glue up stock and the clamp. Why haven't I thought of that already?!

Slick, eh? It's not original though. Probably as old as pipe clamps. I think I pinched the idea from another creeker post quite some time ago.:)

[Rob Will]

You guys were right......the stain is from the Jorgensen pads.

Last night, I set up a test with several different clamps on a scrap cherry board. Some had the plastic pads, some did not.

In every location where a Jorgensen plastic pad touched the wood there was a stain. The plastic pads on other brands of clamps did not leave a stain. None. Zero.

Last year I invested a pile of money in 40 Jorgensen clamps. I felt good about them being USA made. Now I'm not too happy and wondering who developed that lame plastic formula :mad:.

Now that I have a tiny bit of experience with these clamps, I'm wishing they were all Bessey's like this:
http://www.besseytools.com/images/pdf/2k7/WoodBarClampsUS.pdf
I recently bought four of the medium duty Bessey TG5 series at WoodCraft. They are expensive as sin but of very nice quality :).

Rob

[David DeCristoforo]

"... invested...in 40 Jorgensen clamps...Now I'm not too happy...lame plastic formula"

Your clamps are fine. The Jorgensen pipe clamps have been a "staple" in wood shops for a long time now. It's just the "lame plastic" thingies you need to dump. The Besseys are sweet but look at the pics... even those come with those "lame plastic" pads. I could go on a huge rant here about how we seem committed to wasting precious resources on needless junk (that we to refer to as "improvements") like the previously mentioned "lame plastic" things that we got along just fine without for a very long time.....but I won't....

[Rob Will]

The guy has stated that the marks appear even when using a piece of plywood between the clamp pads and the cherry....yet all these replies keep telling him it's the vinyl pads. It can't be!
Look at the picture. The marks are on both pieces of wood which were facing each other.
http://sawmillcreek.org/attachment.php?attachmentid=86898&d=1208748587

Sorry guys,
I failed to tell the whole story (now that we have more information).

Theory 1: After further review, I think that I initially clamped the cherry directly with the clamps. After a few minutes, I added the strip of plywood. OR........

Theory 2: I may have used that strip of plywood in a similar glue-up the day before. The oil from the pads may have soaked into the plywood and the next time that I used the plywood pad, the oil was transferred to the cherry.

Either way, the oil is definitely coming from the Jorgensen pads.
Sorry I did not make that clear but I just today figured out what was happening:o.

Rob

[Paul Simmel]

That's what I'm referring to. Having the stain bleed through the plywood from the pads would be weird, but it could transfer if the plywood had been used before and stained by clamping, and the stained part had been placed against the cherry. I've had it happen.

The first response to the original post:

>>> I have seen this many times with cherry but not with all cherry. I am not sure that it is oils or something else.

I suppose your scenario is a possible one too. The OP is going to have to clear up whether or not he used a stained piece of ply. I've never used the rubber pads, so I wouldn't know.

Also, the "fuss" of the wood may have been compressed and thus "flattened" not "stained" at all. That, I have seen.

[Rob Will]

"... invested...in 40 Jorgensen clamps...Now I'm not too happy...lame plastic formula"

Your clamps are fine. The Jorgensen pipe clamps have been a "staple" in wood shops for a long time now. It's just the "lame plastic" thingies you need to dump. The Besseys are sweet but look at the pics... even those come with those "lame plastic" pads. I could go on a huge rant here about how we seem committed to wasting precious resources on needless junk (that we to refer to as "improvements") like the previously mentioned "lame plastic" things that we got along just fine without for a very long time.....but I won't....

Hi David,
The clamps that I am using are the Jorgensen I-beam clamps.
http://www.sawmillcreek.org/attachment.php?attachmentid=52900&d=1166504040
My other clamp brands with plastic pads leave no stain.
Rob

[Paul Simmel]

Rob,

>>> Theory 2: I may have used that strip of plywood in a similar glue-up the day before. The oil from the pads may have soaked into the plywood and the next time that I used the plywood pad, the oil was transferred to the cherry.

Can you locate the glue up from the day before, and see if the piece is "stained" and/or match the marks from the ply to it? Also, can you just clamp down on a piece of scrap without the pads, to see what happens, and let us know what you see there?

This is now a full-blown mystery. Aside from the "fuzz" issue I mentioned earlier, this is the weirdest thing I've seen in a long time and would like very much to add the answer to my "knowledge base".

Thanks!

[David DeCristoforo]

Those are even better. I have a lot of those too. Not as pretty as yours though since I have been beating them for 25 years now.... The wood pads in Tom's pics work with these too. You just need a slot instead of a hole..... I make them put of 1/2" ply

[Jacob Reverb]

Now that I have a tiny bit of experience with these clamps, I'm wishing they were all Bessey's like this:
http://www.besseytools.com/images/pdf/2k7/WoodBarClampsUS.pdf

You won't get the same kind of clamping pressures with those Besseys as you get with your Pony-type pipe clamps. Look at how much more leverage you get on the handles of your pipe clamps.

Just take the rubber pads off and toss them. None of my dozens have rubber clamp covers, and never a problem! :D

Edit: Oops! I now see you're referring to bar-type clamps. In that case, you probably won't get anywhere near the kinds of pressures you're currently getting with your Jorgensen bar clamps!

[jim gossage]

i have seen the same thing with all of my clamps that have plastic/rubber pads on them. cleaning the pads with mineral spirits does not help. i see it on walnut and cherry. if your clamps are ferrous metal, take off the pads and replace them with little pieces of those refrigerator magnetic thingees that you get in the mail as advertisements. you can also put a piece of blue painters tape over the plastic pad - not very pretty but its quick, cheap, and it has never failed me.

[Mike SoRelle]

Out of curiosity last night, I took a couple of el-cheapo bar clamps that I've had for a few years and have used many times and clamped them both to a scrap piece of pine and lo and behold this morning both of clamp locations had a significant oil looking darkening where the pads had sat.

I've never noticed it since I always use scrap cauls (which I also see the stains on now that I look for them) so I'd say age is not a factor either.

I did use significant pressure for my test since I was trying to squeeze out the goo

Guess the lesson here is to never skip the cauls (or throw the caps away, but I like the anti slip they give while positioning.) I wonder if plasti-dip does the same thing after it's cured?


Mike

[Chris Padilla]

Petroleum products are eeeeeeeeeevvvvvvvvviiiiiiiillllllllllll!!!!!!!!!!

;)

:D