How Do Hide Glue Joints Fail?

[AHill]

I know that PVA joints, if properly glued up, will fail in the wood and not at the joint, but what about hide glue joints?  Will they fail at the glue line or does it take the wood with it?  Just curious, since I haven't used hide glue before.

[Herb G]

Yes, it will fail at the glue line. Hide glue isn't used much these days except for building musical instruments.

[packerguy®]

Hide glue isn't used much these days except for building musical instruments.

Really? I use quite a bit of it. Last year about 10 pounds of granular and a bottle of liquid....It has its place. Now cabinet shops pounding out box cabinets, not so much. Inexperienced DIY'ers....not so much. But I bet many high end furniture makers, and folks that veneer a lot use it quite a bit. Personally, its all I use to veneer anymore. 

I think if more folks got over the misunderstanding/fear of using it, they would love it.  Afterall, if your using proper joinery you dont need much glue at all. Remember they didnt have PVA glues hundreds of years ago....and there is still furniture around from that period that used hide glue.....IMHO a hide glue joint will only fail if the glue is prepared incorrectly, or the joint wasnt solid in the first place.

[Handplanesandmore]

Anyone who has used high glue (hot or liquid) long enough knows what misinformation is. Ten years ago, FW published the test results of breaking point and found:

Liquid hg was 79% joint strength as % of type 1 PVC glue (water proof), or Titebond III, and hot hg at 76%.

To say high glue joints would fail at the joint line is....

To say hg is used mainly by instrument makers is also ....

Simon

[jteneyck]

When I have an application that doesn't need moisture resistance and requires a really long assembly time, I use liquid hide glue.  That's not very often, but over 20+ years I can't recall any joint failures.  One very nice feature of hide glue is you can clean up dried squeeze out with a warm, wet rag.  

I also use it when I repair something that was glued with hide glue.  There are few advantages of doing this.  One, you don't have to get the joint completely clean as new hide glue will bond to old hide glue.  Hide glue has some gap filling capabilities, too, which often is a requirement when gluing old chair joints.  And important in my mind, I'm doing the next guy a big favor, one some previous hacks didn't extend to me, because you can get an old hide glue joint apart with moisture and heat.

John

[Martin S.]

Hide glue is not just for instruments.

Hide glue does not mess with your finish.

Hide glue is easy to clean up.

Hide glue has a longer set up time.

Hide glue can be repaired later, hide glue will stick to itself. Try that with other glues.

Old Brown Glue is readily available from LV, if you don't want to use hot hide glue.

I've made 4 Windsor chairs, all with hide glue. Those chairs will last 200 years, of that I am certain.

I switched to hide glue for my furniture 10 years ago, and I have no regrets.

I am sure there are certain times other glues are better, such as epoxy for boats.

As for me, I'll stick with hide glue.

Herb, don't knock it until you try it.

[Johneone]

Hide glue is my main glue, I only use pva if I need water resistance. I started using it because of the way it doesn't mess with finishes, but found I like its properties such as open time better than pva. I have never had a glue joint fail, pva or hide glue.

[AHill]

Just to be clear, I'm not questioning the strength of hide glue.  I'm just wanting to provide some expert opinion to a friend whose guitar was mishandled and it broke at the headstock.  The headstock (for whatever reason) was attached using finger joints.  The break perfectly separated at the joint line.  Some are suggesting it was a poor glue-up, because it would have uneven separation with wood if it was a proper glue joint.  It was a somewhat expensive guitar, so I am thinking that maybe the finger joints were glued up with hide glue.

[Steve N]

Allan I would think that is a crappy joint for something that is handling the balance and weight of a guitar. Not a lot of weight, but a cheesy joint for that use, plus you may have to question the application, was it sufficient. Older hide glue failures give it a bad reputation, but on furniture over 100 years old the glue may have been made by a farmer using rendered fat, and a seat of his pants recipe. Unless this is an "old" guitar I would think the problem was one of four things, likely a combination.

1) poor joint choice

2) bad application of good glue

3) application of glue too watered down, or too old

4) Your friend has been steaming the neck of his guitar in some manner, and it softened the bond, which is one of it's strengths in use, and can also be a weakness

Because of it's ability to reverse it's hold a fix could be easier than with a different glue, that actually adhered into the wood grains. Heat a liquid will soften what is left.


Not seeing any finger joints

[AHill]

Steve, you've hit on most of the reasons I can think of the joint failed.  You link, however, was pics of neck to body joints.  The referenced failure was neck to headstock.  While not common, finger joints have been used. It just looks ugly.  Most luthiers prefer a one-piece neck that includes the headstock.