# Glue for Bent Laminations?



## CubsFan (Feb 23, 2010)

I'm working on the Morris Chair from Wood Magazine 112 ( http://www.woodmagazine.com/woodworking-plans/furniture/mission/ )

I'm to the point where I need to glue the arms to the form. My question is: what's the best glue? I was just going to use normal Titebond II, but I was at a woodworking show this weekend where Jim Heavy from Wood Magazine was talking about bent laminations, and he recommended polyurethane glue. He likes the extended open time mostly. Now to be fair, he was talking about laminating a drawer front with 10-15 pieces, I've only got 3 pieces total. So open time would be slightly less of an issue for me.

Anyway, any thoughts on the best glue?

Thanks!


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## Loren (May 30, 2008)

Yellow glue can creep from the joints. White glue is less prone to
creep but it still can. I use plastic resin glue for laminations with exposed
edges because it dries hard and won't creep.


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## a1Jim (Aug 9, 2008)

I use resin glue also. Here's a readily available brand.

http://www.amazon.com/00203-Weldwood-Plastic-Resin-1-Pound/dp/B001003J16


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## DLCW (Feb 18, 2011)

I always use plastic resin glue (DAC Woodweld) on all bent lamination work. It has virtually no springback and literally welds the pieces of wood together to become one piece. Another nice feature is the really long open/working time. Upwards of 45 minutes. But you do need to keep it in clamps over night and it needs to stay warm. I use a simple electric blanket drapped over the glue up to keep it warm. You can clamp with conventional clamps or a vacuum press/clamping system. Just make sure you have good even pressure.

I get my Woodweld from my local Ace Hardware. It is a powder and gets mixed with water. Wear a mask!!!!


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## Byron (Nov 19, 2011)

Everyone has their preferences but all glues have their problems. Resin glue requires a TON of pressure compared to yellow glue, but has more open time and less spring back. I know many many people that have had problems using resin glue. Yellow glue seems to always be a surefire glue in general applications. Any time you can use yellow glue I would recommend it, keeping in mind the benefits of the other forms of glue. Epoxy does not introduce moisture into the wood since it is not water based and when working with thin stock is usually a good idea. The downside to yellow glue besides adding moisture is how flexible it is. This flexibility causes cold creep when the layers of laminations expand at different ratios. Yellow glue is the easiest glue to work, there's no toxic particles to mix in, and I would recommend it for normal bent laminations.


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## Byron (Nov 19, 2011)

After looking at this chair it seems like there's not really a need to bend the arms, you can cut them without much if any short-grain, does not really make sense to me.


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## Viktor (Jan 15, 2009)

What Loren said. Titebond and such are PVA glues that creep under significant and constant load. Hide glue does not creep, but it is brittle. In practice this should not make any difference unless you are making a bow.


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## rance (Sep 30, 2009)

This is gonna sound, uh, creepy, but What is creep? I thought once you glued something, it stayed there.


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## CubsFan (Feb 23, 2010)

Thanks everyone! I'll swing by the store tomorrow and grab some glue. Also, I second rance's question


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## Byron (Nov 19, 2011)

If you ever look at a dried glob of yellow glue you will notice it is still pretty flexible and rubbery, but when you look at resin glues and epoxies they are extremely stiff, this means that even though yellow glue gets absorbed into the grain of the wood the bond is still a flexible one, adding much strength to the joint but also allowing the joint to move slightly, so when two different pieces expand and contract at different ratios the joint is allowed slight movement. This is also something that makes epoxies and resin glues slightly less reliable due to the fact they are more brittle and can crack, Idk how much of a problem this actually creates, I don't think I've been alive long enough to know for sure let alone make something that has had to face the standards of time.


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## a1Jim (Aug 9, 2008)

I think of it as wood moving after being under clamp pressure. Here's some Ideas

http://www.craftkb.com/Uwe/Forum.aspx/woodworking/41034/Glue-Creep-Was-Bent-Lamination

or better yet

http://www.adhesivestoolkit.com/Toolkits/DesignGuidance/Creep.xtp


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## shipwright (Sep 27, 2010)

My choice for bent lamination under pressure would be urea formaldehyde or hide glue. Either would be very strong with excellent characteristics. UF would give far more working time but does require good clamping pressure. That said, bent lamination requires good clamping pressure.

Epoxy is the wrong glue for bent lamination unless you are prepared to add a thin cloth or the like between pieces. The pressure required to compress curved laminations will drive too much glue from the joint and it will be dry. Epoxy will not function this way.

Sorry Byron, no offence intended but if you are finding epoxy brittle, you are using poor epoxy. One of the great advantages that epoxies have over polyesters is their flexibility.


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## rance (Sep 30, 2009)

Never too old to learn. Thank you all for the explanations.


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## Nels (Dec 10, 2013)

Not to happy this morning. After gluing 2 chair backs up yesterday afternoon, I unclamped and both failed. Used Titebond III. One broke both glue joints and went back to straight boards. The other one is still curved, but one joint failed. Back to the drawing board!
The gap in the middle board is for the slats on the back of the chair.


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## Hammerthumb (Dec 28, 2012)

How thick are the pieces your laminating? Can't really tell from the picture, but I think the pieces may have been too thick. Maybe try with thinner laminations. As far as glue, I have had real good luck with urethane glue or hide glue, depending on the project.


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## JAAune (Jan 22, 2012)

A few tips that might help.

Use an odd number of laminations. This prevents a useless glue line in the middle that does nothing to help maintain the shape of the part.

You should be able to flex the laminations with your hands close to the shape of the form. If you can't even come close to doing this, the laminations are too think and will be under too much stress. Make them thinner and use more pieces to get the needed thickness.

I prefer epoxy or Unibond 800 for the most critical laminations. Those that aren't under as much stress or those that will be used in places where they are firmly held in place get glued up with Unibond 1 or Titebond III.

If using those powdered resin glues like Weldwood be sure to buy it from a place that moves a lot of product. I'm not positive but I think that's the product only has a 1 year shelf life. If it gets much older than that it'll cause joint failures. I'm also pretty sure the same product will go bad if the lid is left open since it will soak up moisture from the air. Get exactly what you need out of the container then shut it tightly again before proceeding to mix your glue.


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## Tony_S (Dec 16, 2009)

Has anyone on this forum actually experienced "glue creep" first hand? Honest question!

Ive heard and read the term hundreds of times over the last 25 years, but over those 25 years, I've glued thousands and thousands of feet of curved laminated handrail, railing components, curved laminated stringers….Treads of all shapes and descriptions…not to mention all the different personal projects, furniture, hardwoods, softwoods etc.

95% of all this was done with plain old yellow PVA. Not once…ever, do I recall having experienced "glue creep".

Truthfully, Ive always regarded it as BS…a woodworkers myth.

I'd love to hear some first hand info and thoughts on what may have led to the mythical(to me and anyone else Ive ever worked with) creep.


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## JAAune (Jan 22, 2012)

I've see some curved parts slowly open within a couple days of pulling them out of the clamps but that generally not an issue if the laminations aren't made too thick or the part is firmly glued or fastened to some solid object. What it boils down to is that PVA glues just aren't as rigid as adhesives like Unibond 800 but they will hold up just fine if people don't ask too much from them. A Unibond 800 glueup might be fine with 7 layers but the PVA will work fine in the same situation with 9.

One of the earliest laminations I ever did was a 3/4" thick walnut part (1/16" thick plies) bent around a 3" radius to a 90 degree angle. That was done using PVA glue and between moisture from the glue and the severity of the curve none of them retained the 90 degree angle they were supposed to have after they were pulled out of the clamps and allowed to sit for a day. Had I let the parts sit in the clamps for a couple days until the excess moisture was gone and immediately assembled my pieces I doubt I'd have noticed anything.

In most furniture applications curved components are attached to something that renders this a non-issue. Once a handrail is fastened to a wall at three points it can't really change its shape and even if it did, no one would be able to spot slight variations.

In a free-floating application where shape retention is critical I'd just use a rigid glue instead of risking the PVA.


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## Nels (Dec 10, 2013)

The pieces that failed were 1/4" on the outside and the piece in the middle was 5/16". I've reduced the curve and gone to Titebond II. I also brought the glued pieces in the house. It drops to about 40 degrees in the shop at night. The Titebond III didn't seem to hook on to the wood. When the joints failed, there was very little wood that tore off.
The piece on the inside is 5/16" because that's the thickness of the vertical slats on the back of the chair. I made one of these chairs a couple years ago and had no problems. I'm making 12-15 (depending on part problems) of these. I wonder if sanding across the grain with some 120 grits would help the glue hook on?


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## TeamTurpin (Oct 3, 2012)

For critical laminations, I always use marine epoxy. I've never had it fail.


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## Ripthorn (Mar 24, 2010)

TonyS - I have experienced creep in a couple guitars I built. I used Titebond II on one and some other PVA on the other. So yes, it does happen. Depending on the situation, the glue line can either sink or bulge out, both requiring some work if you're that picky.


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## JAAune (Jan 22, 2012)

@ Nels

40 degrees is definitely too cold for any of the Titebond PVA products. Titebond III has the lowest working temperature but I think it's 50-55 degrees minimum.

Sanding won't help a glue joint unless there's contamination of some sort on the surface. In a perfect world, a super smooth, flat surface created by a slicing action such as that of a hand plane is what you'd want for the strongest joint. Ever put water between two pieces of glass then try to pull them apart? That's what wood glue is doing.


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## PaulDoug (Sep 26, 2013)

I guess I lucked out, I use Titebond II on mine and had no problem. Least they are still holding and it's been about 10 years now. I didn't do this on the chair, but I did do it on a coaming for a kayak and it worked real well. I soaked the wood and then bent and clamped it. Let it dry for several days, clamped. Then I undid it and glued and camped it. Coarse the coaming was much thinner pieces and it was much tighter bends.


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## merebe5 (Apr 5, 2017)

Thanks for the helpful info, everyone.

I'm planning to do an epoxy coat on my final project. I'm wondering if that will be stiff enough that even if the Titebond "wanted" to creep, it wouldn't be able to?

Thanks for your comments…


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