Opinions on different glues

[Larry Feltner]

I'm rethinking my choice of using PVA glues. The reason is the ability repair a glue joint failure at some point. I'd like to think that whatever I make is worth repairing and since nothing else sticks to dried PVA glue, I'm not sure it's the best choice.

David Marks makes a good case the urea-formaldehyde glues are a very good alternative to PVA glue. It is a very strong glue and resistant to many chemicals and water damage. The glue doesn't allow joint creep over time like PVA does. The joint is also repairable if it fails. I haven't tried them but they seem like a very good alternative. The only concern I have with them is that there are health concerns associated with formaldehyde. Some people have allergic reactions to it, and some studies suggest it is a cancer causing agent. I'm not sure glue joints in furniture would leach enough gas into a home to be a concern or not.

I've also considered hide glue. It isn't as strong and resistant to water, etc., as some of the others, but it is still stronger than the wood itself. I haven't tried it, but it has a long history of performing well and it is certainly very repairable.

I doubt that any glue is perfect. So I'm curious as to what others thoughts are on the best compromise glue for woodworking.

[Jerry Thompson]

I use Old Brown Glue. It is hide glue in a bottle. It takes a long time to cure. I find this as a plus in many cases. If I can do a job quickly I use hot hide glue. They are not tolerant of water for any length of time.
However furniture does not normally get wet unless it is for outdoors.
The glue will stain and if one makes a mistake it can be taken apart using water to dissolve the glue.
You are right no glue is perfect.

[Jamie Buxton]

I'm not sure I understand the concern about regluing a PVA joint. A properly-made PVA bond is stronger than the wood around it. Try making a simple butt joint, facegrain to facegrain, using PVA. Stress it to the point of breaking. The wood will go, not the glue. If you have a PVA joint fail, there's something wrong in the woodwork. You need to find that and correct it, rather than just pumping more glue at it.

Urea formaldehyde is a good glue -- strong and creep-free. It has a few drawbacks. One is that you have to stop to mix the stuff up. Another is that UF will not cure correctly below 55 or 60 degrees -- check your manufacturer's instructions. There's also the formaldehyde issue. But if you're concerned about formaldehyde, you can use epoxy. It is strong, creep-free, and requires mixing, just like UF. Unfortunately, it is about three times the cost of UF.

Me, I use PVA for most work. I use UF for bent lamination, and for complex assemblies when I need the long open time. I use epoxy to bond wood to metal.

[Larry Feltner]

I'm not sure I understand the concern about regluing a PVA joint. A properly-made PVA bond is stronger than the wood around it. Try making a simple butt joint, facegrain to facegrain, using PVA. Stress it to the point of breaking. The wood will go, not the glue. If you have a PVA joint fail, there's something wrong in the woodwork. You need to find that and correct it, rather than just pumping more glue at it.

Urea formaldehyde is a good glue -- strong and creep-free. It has a few drawbacks. One is that you have to stop to mix the stuff up. Another is that UF will not cure correctly below 55 or 60 degrees -- check your manufacturer's instructions. There's also the formaldehyde issue. But if you're concerned about formaldehyde, you can use epoxy. It is strong, creep-free, and requires mixing, just like UF. Unfortunately, it is about three times the cost of UF.

Me, I use PVA for most work. I use UF for bent lamination, and for complex assemblies when I need the long open time. I use epoxy to bond wood to metal.

I guess I should have been more clear. I'm not having joint failures with PVA. I'm speaking down the road, perhaps long after I'm dead and gone. I'm just saying I would like for the joint to be repairable in the event that at some point in its life there is a glue failure. None of us can say that a joint constructed with PVA glue will last indefinitely. I'm just thinking long term and what glue will best serve the survival of whatever pieces I build over the long term.

[Jamie Buxton]

... None of us can say that a joint constructed with PVA glue will last indefinitely....

PVA has been used as a wood glue for fifty years now. Manufacturers and academics have done accelerated aging on it. Nobody has evidence that it degrades with time. There are probably other issues in your woodworking that deserve more concern than this one.

[david brum]

Larry,

You can definitely take a PVA joint apart. I recently screwed up a gluing job on some table legs. After a bit of research, I found some info about how to soak a glued joint in hot vinegar. Sure enough, the vinegar temporarily softens PVA glue enough to get the joints apart. I pulled apart fairly large mortise and tenon joints, so it should work on most joints. I'm sure that any furniture restorer knows this trick.

I also have a luthier friend who uses steam to get musical instruments apart when they've been glued with PVA.

Not to dissuade you from different glues, but PVA is certainly reversible.

[John Coloccia]

Titebond has pretty much become the standard luthier glue. I use a different PVA that's harder and with less creep for certain joints, and sometimes hide glue too. These are highly stressed joints, though. I can't think of a joint on furniture that should ever be stressed like this. The glue should just keep the joinery from slipping apart so there shouldn't be much stress on any of it.

If you need more time, there's an extended time Titebond. Once you're into it, though, hide glue can be quite pleasant to work with. I don't see that experimenting with different glues is a bad thing. Personally, I see no reason to regularly use any glue that has toxic properties when there are plenty of glues available that don't. I occasionally use nasty glues, mostly for bent laminations when I need a LOT of time to do my glue up.

[Shawn Pixley]

Having repaired a lot of furniture, I'll echo that PVA joints can be repaired. Hot vinegar will open most joints. The trick when you or I are dead and gone is who will repair the joint or piece if there is failure or damage. About half the repairs I did were broken pieces not failed joints. Unfortunately often the broken piece necessitated the opening and regluing of joints. I noticed chair joints failing the most. Primarily on turned legs set into the seat. The balance of the repairs were from the owner stripping the furniture and loosening the joint through the use of harsh strippers (but at least they raised the grain).

[Jack Clark]

Although the link below is not about glues for joinery, this information may enhance this discussion a little.

https://www.vacupress.com/forum/thread-view.asp?threadid=17037&posts=5

[Chris Fournier]

I think that it is very important to carefully consider which glue you are using for any given task. Points of concern are mechanical properties, compatability with post glue up processes, ease of use, toxicity, shelf life and cost/value to list a few.

For the bulk of most woodworking PVA is very tough to beat as a first choice.

While I haven't been woodworking for 100 years I can say that a glue joint failure is a very rare occurance and I can usually predict one during a poor glue up which means that I can redo the joint or glue up process to ensure success. More of a craftsmanship failure than a glue failure (this also goes for poor mixing and glue up temperature control errors).

I inventory and use about a dozen different glues in my shop. PVA is number one without a doubt. As has been mentioned there are many different PVA formulations that give your properties which are key to certain processes. Check out an adhesive/finishes supplier for a mindnumbing array of PVAs.

Next to PVA I use a lot of Palstic resin glue (urea formaldehyde), both in the Urac 185 two part format and in the Precatalysed Plastic Resin powdered format. I find that the Urac 185 wets better than the powdered product but it is fussier to use and the formaldehyde off gassing is more noticable than the powdered product. Nonetheless I couldn't imagine being without these glues where creep resistance is critical. As a bonus they also sand beautifully. As a caution, the squeeze out is as sharp as glass and lacerations are pretty much inevitable - be careful!

Polyurethane, Urethane, "crazy" glues, epoxy, contact cement, resorcinol are a few more useful glues. In your spare time read up on their properties and buy small quantities to do testing and gain experieince with them. First hand experience beats free advice every time when it comes to knowing which glue to use for a given task. Destructive testing on test joints can also help you improve your glue up technique - look for starved joints, fibre transfer, excessive squeeze out etc.

[Larry Feltner]

After posting this topic, I found this excellent thread about the characteristics of various glues. As I have always been told, the person who started the thread indicates that virtually nothing sticks to cured PVA glue. Therefore, anything made with PVA glue is difficult to repair short of re-cutting the joint.

Anyway here is a link to the thread if anyone is interested in reading it. It really has some outstanding information.

www.sawmillcreek.org/showthread.php?p=195012&highlight=plastic+resin+glue (http://www.sawmillcreek.org/showthread.php?p=195012&highlight=plastic+resin+glue)

[David Weaver]

Back to the original question, liquid hide glue. Long open time, easy to clean up, strong.

I don't build stuff that goes outside, so moisture isn't really a concern.

I do still use PVA on stuff, but usually things I don't care about, like shop jigs, etc.

The only problem with liquid hide is that it's sometimes out of stock locally and it doesn't have a long shelf life.

[Chris Padilla]

PVAs are way too convenient and easy and strong to not use nearly all the time.

I do use a harder curing glue for my veneering but PVA is king for me.

[Martin Shupe]

Another vote for Old Brown Glue.

Slow cure time, good for complicated glue ups.

No problems with glue interference with the finish.