# Inexplicable glue failure?



## Jimothy (Oct 29, 2015)

So I made a serving platter made of various woods. For the life of me I can't remember what the problematic wood species was, so let's call it X. There were multiple spots where X was glued to oak walnut and cedar. All points where X was glued to cedar failed with little force, while all the other edges glued fine. I know there can be problems glueing dense woods due to it being hard for the glue to penetrate, but it glued to other woods just fine.
Plus the cedar was glued to other edges that worked fine too.

Any idea why it would glue to all woods except one?


----------



## TheFridge (May 1, 2014)

Don't know. Wipe with acetone right before gluing next time. Not much more you can do to provide an ideal surface for gluing. And I wouldn't glue them back together without cleaning up the old glue.


----------



## redryder (Nov 28, 2009)

Cedar…...naturally oily. Resistant to rot, insects and it smells good.

Check out this articlehttp://www.wood-database.com/wood-articles/gluing-oily-tropical-hardwoods/ about doing glue-ups with cedar…......................


----------



## wapakfred (Jul 29, 2011)

What Mike said, it was the oils in the cedar.


----------



## bigblockyeti (Sep 9, 2013)

Was it some other exotic wood that might have an even greater oil content than cedar? I use Titebond II for almost everything and I've never experienced a failure when gluing cedar to cedar or to another wood.


----------



## dddddmorgan (Apr 24, 2015)

Agree with advice given above, especially about prepping the surface. This is why I use my biscuit joiner if there's any doubt in my mind.

No, I don't have money for a Festool, my PC joiner has served me well for years.


----------



## JBrow (Nov 18, 2015)

Jimothy,

Without seeing the project and the glue line failure, it is impossible to attempt to pin down the reason for the glue failure. There are several circumstances that can lead to glue failure. Here are the ones that occur to me:

1) A gap exists between the surfaces to be glued. Glue will bond but is a poor gap filler.

2) The glue skimmed over before clamping. This is a problem I have dealt with. For example, if the glue-up is large and by the time glue is applied to the last the surface, the first surfaces have skimmed over, the skimmed over up edges will not bond well, while other surfaces bond well.

3) Glue was not applied to both mating surfaces. Both mating surface must receive glue for the best bond. Some glue requires it to be applied to only one surface.

4) The glue was not spread evenly on the mating surfaces. Glue must be spread over the entire surface for the best bond.

5) Too much clamping pressure was applied. Too much clamping pressure can squeeze too much glue out of the joint, leaving little glue for bonding.

6) Too little clamping pressure. The mating surfaces must be brought into intimate contact for the glue to yield the best bond.

7) Removing the glue-up from the clamps too soon. If the glue does not have the change to completely cure, the joint can be weakened. Curing time is dependent on the temperature and humidity during the glue up.

8) An unreinforced end grain joint was glued. End grain soaks up the glue leaving little of it on the surface for bonding.

9) The wood on the mating surfaces is old wood. Best result are obtained when the mating surfaces are freshly milled, allowing for greater glue penetration.

10) Failure to heed glue instructions can weaken a glued joint. Performing a glue-up when the temperature is too low, or failing to dampen mating surface for polyurethane glue can have adverse effects.

11) Cleaning up glue squeeze out with a wet rag. Some remove glue squeeze out, me included at times, by wiping excess glue from the surface with a damp rag before the glue has cured. If the rag is too wet, water can seep into the joint and around the joint and dilute the glue or otherwise affect the glue bond.

12) As already mentioned by others, for some woods, oily surfaces can inhibit glue from bonding to the wood.

13) The cured glued joint was exposed to excess moisture. After a non-water proof or non- water resistant glue is exposed to high moisture for a period of the time, the joint will fail.

14) Differential expansion and contraction of different woods, occurring only at the glued joint, can lead to failure. Differing woods have different properties, including the degree of expansion and contraction. This wood movement cannot be restrained and is exaggerated when long grain is glued to end grain.


----------



## Jimothy (Oct 29, 2015)

I thought about the oiliness of the cedar and the other wood, but they both glued fine to other species.


----------



## ALMC (Feb 10, 2016)

Teak is tough to glue dense and oily


----------



## gargey (Apr 11, 2016)

> 5) Too much clamping pressure was applied. Too much clamping pressure can squeeze too much glue out of the joint, leaving little glue for bonding.
> - JBrow


Myth


----------



## JBrow (Nov 18, 2015)

gargey,

I too have heard that starving a glue joint with excess clamping pressure is not possible. I also have heard that excess clamping pressure can starve and weaken a joint.

In the video entitled Application Help - Edge Gluing, with Jim Heavey, evidently produced by Titebond, Mr. Heavey indicates that excess clamping pressure can force glue from the joint and thereby reduce the amount of glue available to form a good bond. Since this video is featured on Titebond's web site, I surmise the company endorses Mr. Heavey's recommendations.

The video is among a series of glue tip videos and by my count the Application Help - Edge Gluing video is the eighth video. All are short and informative.

http://www.titebond.com/newsarticle/13-05-01/VideoSpotlightClampingPressure.aspx


----------



## Tony_S (Dec 16, 2009)

> Mr. Heavey indicates that excess clamping pressure can force glue from the joint and thereby reduce the amount of glue available to form a good bond.
> - JBrow


I watched the video 4-5 times and I didn't hear him say any such thing.
This quote is as close as I can come, but still, in my opinion, can't be translated as such.

"Using clamps to force poorly fitted edges together will result in uneven pressures along the glue line, and the stress to return to it's previous shape will plague the glue up once the clamps are removed."

I interpret that statement to mean that you will get cracks/splits 'somewhere' in the glue up once the clamp pressure is relieved, depending on how large, and the location of the gaps. (I guess I'm using my professional experience to interpret)

Ive found that most often,(if the glue is allowed to cure sufficiently) these cracks/splits will usually occur near, but not directly on the glue line it's self, particularly at the ends of the boards. splits midfield are a lot less common, but nearly always happen very near the glue line.

Op.
Assuming your starting with near perfect straight, square edges, try cleaning both surfaces with acetone pre-glue up. That should solve the issues your having. I've also found that TB III works much better on oily woods.
(unless your trying to glue Ipe….then burn it.)


----------



## JBrow (Nov 18, 2015)

Tony S,

Indeed Mr. Heavey makes the point you paraphrased in the first of the series of glue-up short videos.

He made the point that excess glue pressure can force glue from the joint and weaken the glue joint. In my previous post I indicated that it was in video 8 in the series when it is actually in video 9 entitled Application Help - Edge Gluing at about 0:30. He states that excessive pressure can reduce the amount of glue in the joint. An amount of glue less than the optimum amount of glue recommended by the manufacturer can only reduce the strength of the joint when compared to the optimum amount of glue.


----------



## bondogaposis (Dec 18, 2011)

I have found that cocobolo is very hard to glue.


----------



## Tony_S (Dec 16, 2009)

> He states that excessive pressure can reduce the amount of glue in the joint.


Yes he does, but he doesn't state that over clamping will weaken the joint to the point of failure, or otherwise. 


> An amount of glue less than the optimum amount of glue recommended by the manufacturer can only reduce the strength of the joint when compared to the optimum amount of glue.
> - JBrow


I can't argue that point, but what I can argue, is that even extreme over clamping will not weaken the glue joint to such a degree that the glue joint will fail before the wood does. It doesn't happen to any degree that's even remotely concernable.
I'm not getting this stuff off the internet. I'm talking about real life and a **** load of experience. Nearly 30 years of bent lamination, edge gluing, face gluing, huge volumes of (mostly) hardwood lumber over that time span on a commercial level. 
Stringers, handrail(straight and curved) solid posts, hollow posts, treads…and a myriad of other products over the years.
I'm the foreman, and I'm a bitch about quality control. If it was an issue, I would have come across it at some point, but I haven't.
I'm not trying to bust your balls JBrow….your one of a hand full on this forum that Imo usually gives fairly clear accurate advise, but your stance on this is wrong in my experience.

Sorry, I sound like a snot….but this topic is a pet peeve of mine.

Btw…for others…all this is referring only to PVA adhesives.


----------

