Official Luthiers Forum!

I saw this article in Fine Woodworking that some of you may have already seen. It tests several types of glues on different woods and joints to see which is strongest. There were definitely some results that surprised me. You can check them out in the link below.

http://www.oldbrownglue.com/pdf/HowStro ... ue_FWW.pdf

_________________
Brad

Great info! Thank you!


Sent from my iPad using Tapatalk HD

_________________
Doug

Don't let fear or common sense stop you from trying to build something

Indeed, it's always nice to see charts like this.

I'm surprised how much stronger the PVA is than hot hide, as well as how little the hide weakens on looser joints. I've always heard, and experienced, that hide glue needs as much direct surface contact as you can get, and the strength drops off quickly on imperfect joints.

The one area of lacking on these tests is the tonal inference. I will also add that when building a guitar , or any instrument for that matter , the joints integrity is the key for the best results. Sloppy joints just don't cut it in a fine instrument .

_________________
John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

Thanks, Brad. Very interesting - I've pretty much been using Titebond II on most joints. I like the yellow glue because I thought it was reasonably strong, but also like how easy it to handle and clean up. These results up my confidence level with this glue. Was somewhat surprised by the epoxy results. Thanks again for the post.

I'd say strong to quite strong.

_________________
http://www.CostaGuitars.com
PMoMC

John, I completely agree with you, and I use hide glue as many places as I possibly can within the shortened open time and my current skill/speed level. I wasn't surprised to see TB2 as strong or stronger than hide glue, but I was surprised to see that room temperature hide glues mixed w/ urea were as close to the heated granular hide glues in their testing. I'd like to see where fish glue falls into the mix, as I'm going to be using it on my current build where hide glue isn't ideal yet for my skill set.

_________________
Brad

I'd recommend Titebond Original over 2. You don't need/want waterproofness, and II dries a little less hard. There have also been reports of more creep with II vs. Original.

Regarding the test, none of those joints were clamped properly. Just slip fit so they were 'tight', which is about how tight I fit an electric guitar set neck, for example, but I still clamp that. All the glue tests I've done with hot hide and similar simply break the wood, not the joint. So I'm not sure the hot hide vs. bottled hide results here are what I'd call representative for instrument joints, where we don't tend to accept a finish straight off a table saw blade as 'good enough'.

Bottom line seems to be that most any glue will do, if used correctly. Polyurethane works great if you clamp it HARD with good surface prep, for example, as the glue expansion will push joints apart and the foam has zero adhesive power.

I found it interesting that they didn't seem to actually clamp the joint, just clamped the wood to the glass. I wonder if that makes any difference. I too wish they had tested standard Tightbond and also wonder where fish glues falls in the continuum.

Alan D.

Based on these reslts I'd say clamping would make a difference.

In the test it says that the tight joints needed a light tap to put them together.

So the tension of the joint would exert what i consider to be a light clamping pressure.

It was also the strongest joint on average.

They used ample glue and weren't worried about squeeze out.

_________________
Old growth, shmold growth!

But still all things being equal are we to throw out the window epoxy as a gap filling glue advice?

I wouldn't get in the habit of relying on any adhesives being a reliable gap filler. That's the beauty of HHG and fish glue. You can easily release any bad joints, and get it right the second time. I'd personally would rather not know about any adhesive that makes a great gap filler, because if I knew I could rely on it to correct my mistakes I would most likely lose focus on what's most important, which is improving my sloppy woodworking skills that caused the inadequate joint to begin with. I didn't have a second thought about rejoining the top on my first guitar build for the current challenge competition. Structurally it would have held up, but it wasn't where it could of been visually or structurally had I done it correctly the first time. Heated the joint to release the hide glue, and reworked it to get a tighter joint. Ultimately, I'm much happier with the results the second time around, and it only added 10-15 minutes of work to make it right.

_________________
Brad

Epoxy wasn't even the consistently strongest glue, and it also lost strength on having a gap.

I would say, yes, if you're relying on it for gap strength, but no, if the goal is to fill the space. Epoxy doesn't shrink as it cures, the way the drying glues do.

I once glued a neck back together that was missing wood, and I glued it together with epoxy, which filled the gap, and when I sanded and finished it with a solid color, it was an invisible repair, although if you were to sand the finish off it kinda looked like a mess!

It held though, and I'm sure it's still together although it was ten years ago. The customer still brings me work and he's never mentioned it coming apart.

_________________
Old growth, shmold growth!

They also didn't take into account how a glue reacts to heat and humidity. Tonal interference, as John so aptly put it, has two parts, hardness of the dried/cured glue (or lack thereof) and also creep, which is somewhat related. This is partly why some glues are better than others for some applications.

_________________
"I want to know what kind of pickups Vince Gill uses in his Tele, because if I had those, as good of a player as I am, I'm sure I could make it sound like that.
Only badly."

FWW is no longer the publication it once was. I used to buy every issue, whereas I'll sometimes go years without getting one. The glue comparison looks to be a page filler.

Alex

_________________
"Indecision is the key to flexibility" .... Bumper sticker

This was my first thought when I saw this thread. I choose a glue for its workability related to a particular operation and never think twice about its strength. For instance, I use HHG for bridges because I know that if I don’t get it clamped down properly, I can easily re-do it, I use PU for neck lams because I never want it to come apart. . .

_________________
Bryan Bear PMoMC

Take care of your feet, and your feet will take care of you.

This article goes back a few years and I have always taken issue with it. There is no good reason to deviate from ASTM D-905 using large sample sizes. Wood has its greatest strength in shear and parallel to the grain. This is marketing propaganda at best. If you need further evidence, take a look on titebond.com and you will find a link to this exact article in support of Titebond III. If anyone wants some good clean test data there is a chance someone in the tech group there might be willing to send you results from competitive analysis testing. Unfortunately, there is no guarantee that they will simply respond with the "typical values" assigned by marketing. For example: on their website TB III has a listed shear strength of 4000 PSI. That number came from an experiment with 15 samples and 4000 PSI was an outlier... However, a lab employee was nevertheless required to sign off on it as a "typical" value. On some particularly strong pieces of maple I once ran a D-905 series with Titebond Original that averaged over 4000 PSI. The important lesson is that any quality wood glue is more than capable of handling the stresses of string tension and that wood is a significant variable. If I can find any of my old test results I will be happy to share them.

With all the testing irregularities aside, it is still interesting stuff. What surprises me most is the poor performance of poly glue, the low values for epoxy, and the high results for premixed hyde glue.

_________________
Joe Beaver
Maker of Sawdust

As others have pointed out, there are many characteristics other than strength that are important in any type of woodworking.

For example, the problem with room-temperature hide glue is not strength, it is short shelf life. When new it's fine, but after it's expired it glues about as well as Log Cabin syrup. Yet it doesn't taste good on pancakes.

Good quality epoxy has advantages in that it doesn't introduce moisture into the wood, can fill large gaps (far larger than the ones in this article), and can be easily unbonded with modest warmth.

With the exception of the performance of the PU glue they used, almost all of the differences between the glues are very very slight. As is unfortunately typical of FWW comparisons, there is no way to know how random variation from instance to instance, and sample to sample, might have changed the findings.

As has been said previously, as long as you're not using outdated glue, or wheat paste, and your joints fit, other glue characteristics such as reversibility, degree of resistance to heat matching use, tendency to creep, cost, toxicity, etc., are far more important than .5% more or less strength.

_________________
Tim Allen
"Never hurry, never rest."

I posted this article over at KGF the other week. Everyone loves the numbers game, but to me the important things are the conclusions on the last page under what we learned about glue. That's the meat and potatoes of it, the numbers are just a way to arrive at a conclusion. I would like to also add that Fine Woodworking magazine has a reputation for rather fair and unbiased testing of products. I have seen them rip up some of their advertisers over the years. So as was pointed out any of these glues will easily hold the stresses of musical instruments, I think John is onto something with his ideas about sonic transduction being more important in some instances. But this needs some form of scientific study to draw those conclusions, another numbers game.

_________________
Brian

You never know what you are capable of until you actually try.

https://www.howardguitarsdelaware.com/

I used epoxy tonight to glue my ski boot together, snow is falling and I want to hit the trails tomorrow, hope it holds the gap fill!

...

hugh.evans in all fairness to the article, I was thinking the same thing, and it's an old brown glue PDF apparently and they didn't put their results on the top of the list. Having looked into old brown glue myself I have seen less than desirable results from luthiers kind enough to provide tests with it.

...

It's just one test which has not been replicated so it's not really 'science' at this point but it is an interesting test and looks to be well controlled for that one instance.

Grain of salt!

Even with the best of intentions and a good track record for honesty, it's still not uncommon to find problems with magazine test results. A personal favorite example of mine was an article published in Consumer Reports well over a decade ago in which several popular wood glues were tested. Two of the products assumed to be different were actually the same formula (common marketing practice) yet their results indicated one literally blew the other out of the water. The important point to take away is that when it comes to adhesive strength: take everything while a few grains of salt.

The best way to view adhesives is as tools. In some situations, perhaps a slotted screw with a hex head, a screwdriver can do the job just as well as a 6-point socket on the end of a ratchet. In others, there is clearly one proper tool for the job. Adhesives selection comes down to substrate compatibility, performance requirements, and compatibility with the process in question. Understanding the inherent differences between adhesive families, handling properties, performance, etc. are the details that make it more challenging. At some point I intend to either write a short book or collection of articles to make it all much less of a mystery.

Interesting article and replies. Thanks for posting.

I would have liked to have seen a test done on the much more common gluing techniques we all use every day that require some clamping instead of the joint the used that I seldom if ever use. Also surprised about PU glue. Thought it was one of the strongest glues out there.

No test on CA either which is probably not becoming more main stream in wood working shops, but curious none the less.

_________________
Thank You and Best To All

Gorilla has done nothing short of a fantastic job marketing their product. Polyurethanes, in my experience, are best suited to special applications. In terms of performance as wood glues they are not far from epoxies, and are exceptionally brittle. They are among the most prone to true adhesive failure, particularly when exposed to shock. CA was most likely excluded because the method in this article applied shear stress (parallel to the glueline.) For most adhesives, shear is the strongest direction and this is also true for wood. However, CA is very weak in shear and strongest in tension. In fact, it is commonly used for sheet metal operations where it is useful to tack a work piece in position quickly and then giving the edge a quick whack with a hammer to separate it. One point definitely worth noting for anyone doing spot repairs with CA is to never use activator spray if it can be avoided. Strength is decreased and the adhesive is more likely to become opaque due to stresses induced by the accelerated reaction. I have personally seen strength losses approaching 50% due to the use of activators.

ROFLOL...

_________________
"I want to know what kind of pickups Vince Gill uses in his Tele, because if I had those, as good of a player as I am, I'm sure I could make it sound like that.
Only badly."