Glue Failure? How likely?

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Forum topic by Ivan posted 04-15-2009 05:13 PM 2108 views 0 times favorited 24 replies Add to Favorites Watch
View Ivan 's profile


185 posts in 3945 days

04-15-2009 05:13 PM

Topic tags/keywords: glue question joining

Well, I’ve been doing some reading on glue joints and the talk of glue failure and the possible advantage of using pinned M&T joinery.

My question is, how likely is glue to fail?

Are there circumstances that will accelerate or promote glue failure (short of leaving it outside in the rain for a week)?

In particular I’m thinking of furniture projects indoors using a Type II PVA (Titebond II).

All the articles now state that the glue joint is stronger than the wood around it, this leads me to believe that the glue is a ‘permanent’ bond and that I’m making much to do about nothing.


-- "Do it right the first time, you'll just kick yourself later..."

24 replies so far

View childress's profile


841 posts in 4110 days

#1 posted 04-15-2009 05:18 PM

If glued correctly….that is, if your glue joint is no bigger than 5 thou it should never fail. Like you said, the glue is stronger than the wood itself….if done correctly. If the joint is sloppy and you try to accommodate this by using more glue to “fill” the gap. Then yes, there will eventually be glue joint failure.

-- Childress Woodworks

View jerry mayfield's profile

jerry mayfield

36 posts in 4653 days

#2 posted 04-15-2009 05:23 PM

Most of the additional mechanical fastening was done before the advent of the modern woodworking glues,they are used now because we like how they look or to show-off. If you are expecting (hoping) a piece to last 100 years or more then some kind of fastener is a good idea.


-- jerry,mlchigan

View Dick, & Barb Cain's profile

Dick, & Barb Cain

8693 posts in 4867 days

#3 posted 04-15-2009 05:28 PM

I have never had a glue failure, except for the hot glue gun type.

Carpenters glue works great.

-- -** You are never to old to set another goal or to dream a new dream ****************** Dick, & Barb Cain, Hibbing, MN.

View Tim Pursell's profile

Tim Pursell

499 posts in 4350 days

#4 posted 04-15-2009 05:38 PM

“How likely is glue to fail?”
Depends….. How well is the piece designed?, How much stress is the joint going to be put under? How much expansion/contraction is the wood likely to endure over the expected lifetime? Do you want the piece to become a familt heirloom? Or is it going to the dorm? Is the wood you’re using oily(teak for one). TitebondII is a great product, but it hasn’t been around 100 years. No one answer is going to cover this question, just as one glue is not the answer for all joints. When I build my lamp shades I use 3 different glues for different joints & I still worry because the thinness of the pieces precludes the stronger designed joints I would prefer to use.


View Francisco Luna's profile

Francisco Luna

969 posts in 3961 days

#5 posted 04-15-2009 06:02 PM

I agree with that last statement. the other day I was trying to split a board through a glue line, but the wood failed first…
For a few bucks more, I would upgrade to Titebond III, the “ultimate” thing, it’s the best!
The secret of gluing are Clamps, the more you use, the better, the thinner the glue layer, the stronger results.

-- Nature is my manifestation of God. I go to nature every day for inspiration in the day's work. I follow in building the principles which nature has used in its domain" Frank Lloyd Wright

View HokieMojo's profile


2104 posts in 4296 days

#6 posted 04-15-2009 06:59 PM

does anyone know if glue actually weekens the wood next to the joint? Anytime I see a test for glue failure, the break is always right next to the glue. I’m wondering if the curing process somehow stresses the wood fibers and weekens it.

View Brad_Nailor's profile


2545 posts in 4525 days

#7 posted 04-15-2009 07:16 PM

From what I have read you only need glue coverage thickness in the 1-2 mm range for proper adhesion. You can over tighten the clamps and squeeze out the glue. A Fine Woodworking article on glue ups had a great tip..tighten the clamps with your off hand as tight as you can, that is ..if your right handed tighten the clamps with your left hand as tight as you can. The only failure I have ever seen on a glue up is when your trying to glue end grain to end grain. Aside from that the wood will fail before the glue joint will if done properly.


View PurpLev's profile


8553 posts in 4216 days

#8 posted 04-15-2009 07:48 PM

glue failure is very unlikey… wood will fail first – IF the glued edges are long-grain to long-grain…

if it’s end-grain to end-grain or end-grain to long-grain, then the glue might fail, but thats where joinery comes to play. one of the benefits of using M&T, dovetails, and box joints is that they introduce long-grain to long-grain in a situation where otherwise it would be long-grain to end-grain thus creating a strong glue platform.

-- ㊍ When in doubt - There is no doubt - Go the safer route.

View PurpLev's profile


8553 posts in 4216 days

#9 posted 04-15-2009 07:52 PM

HokieMojo – the reason you see the wood fail NEXT to the glue joint is not because the glue weakens the wood there, but because the tests that are run, are focusing the tension/pressure on the glue joint itself so thats where the force is applied… since the glue joint is stronger than the wood, the wood that is closest to the location where the force is applied is the one that breaks- read- the wood next to the glue joint (closest wood to where the force is applied)

-- ㊍ When in doubt - There is no doubt - Go the safer route.

View Ivan 's profile


185 posts in 3945 days

#10 posted 04-15-2009 09:04 PM

Excellent advice. Thanks so much.

Reason i’m asking is that a friend has asked for a trunk that she will be actually using for travel and I’m worried about the glue joints being exposed to abuse.

I understand the more long grain contact the better and that end grain really doesn’t adhere.

Fasteners are still an option and I think I might use some nice contrasting plugs for that end.

I have used Titebond III for some time, but the cost difference (they are next to each other on the shelf, what better comparison can you make?) is what has driven me to use Titebond II most recently.

I’ll trust the glue joint and add some fasteners where I think appropriate, now if I could only find hardware that I like…


-- "Do it right the first time, you'll just kick yourself later..."

View johnpoolesc's profile


246 posts in 3928 days

#11 posted 04-15-2009 09:12 PM

if the joint is tight.. not so tight that it does not leave room for glue, and the wood is fresh sanded or milled. 40 plus years, zero glue failure..

-- It's not a sickness, i can stop buying tools anytime.

View HokieMojo's profile


2104 posts in 4296 days

#12 posted 04-15-2009 09:15 PM

That makes sense. Maybe I’ll try to confirm someday by gluing a 4 inch board to and 8 inch board and seeing where the split happens when presure is put right in the middle. Then again, it might just test how bad my glue joints are. thanks.

View HallTree's profile


5665 posts in 4335 days

#13 posted 04-15-2009 09:19 PM

I just finished reading an old Fine Woodworking article (11/1987) ‘Coping with Failing Joints’ by Bob Flexner. If any of you have that issue it is worth reading. The part that stuck in my mind was Bob’s statement ‘There is, In short, no known way to bond wood together in cross-grain direction and expect it to survive in everyday use for more than 50 to 100 years. Everything we build or repair will come apart sooner or later.’ He also states ‘A woodworker or restorer should pick a glue that can be removed easily and with little damage to the joints, so that the furniture can be reglued effectively in the future. It’s wiser, therefore, to build or repair with future repair in mind than with hopes for permanency.’

-- "Hold on to instruction, do not let it go; guard it well, for it is your life" Solomon

View motthunter's profile


2141 posts in 4367 days

#14 posted 04-15-2009 09:30 PM

Using the right glue for the job, and the glue is fresh… it should never fail.

Now if you want to pin for more strength, thats great, especially if you use a contrasting pin to make the joint even more visually interesting.

-- making sawdust....

View Ivan 's profile


185 posts in 3945 days

#15 posted 04-15-2009 09:58 PM

I read one of the articles on glue strength and was pleased to see that the Poly glue did not fair all that well.

I made a desk with the Gorilla glue and to be honest I didn’t like using it, too much mess and fuss (pre-wet dry surfaces, clamp quickly, etc…) but the desk has not come apart in over 8 years.

I suppose that if I want this to last ‘forever’ I’ll make it out of diamonds. Realistically I’d be thrilled to get 50 years from a piece that will see real use.

Thanks again,

-- "Do it right the first time, you'll just kick yourself later..."

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