for table top glue-ups: what glue do you use?

[mikefm101]

The only time I’ve ever had joints fail is when I used polyurethane gorilla glue. White oak outdoor seating. Mortise and tenon joints were loose and a decorative part of the back fell off.

I think it was FWW magazine had a test years ago and TB held up better than most if not all other options tested.

The clean up with poly is a drag. Scraping the foam off and brown stains on everything.

For a table used indoors any TB will suffice. After it cures the glue is stronger than the wood.

Mike

[adamcherubini]

I'm pretty familiar with glues but not polyurethane so much. I trust Chris Schwarz, who wrote about this subject many years ago. Bottom line: PVA is superior for long grain well fitting joints, clamped up and producing no visible seam. The glue all of us have been using is the right one. Poly will work, but isn't stronger and requires different clean up (like lacquer thinner wipes).

Polyurethane glues excel at joints involving end grain. At the office, we talk about surface wetting. I think that's what poly does better than PVA.

For joints that can't be clamped (mortise and tenon, dovetails) or are gappy for whatever reason, either hide glue or epoxy are our best choices. The choice between them often comes down to person preference or availability, but the decision doesn't need to be subjective.

My contacts in the museum world believe that the longevity of 18th c furniture has a great deal to do with the lack of fasteners and the use of hide glue which is both reversible and reactivatible (new glue sticks to old glue). If you are building for 100yrs or are looking for repairability, hide glue is the right choice.

Epoxy's benefits are that you can custom design its open time, accelerate cure with heat, and can mix stuff in it to make it thicker without losing strength. Its properties don't change with humidity. Like PVA, its chief disadvantage is that it must be 100% removed to facilitate a new bond and will likely damage underlying wood during disassembly.

The key to working with both hot hide and epoxy is the key to understanding why we like PVA so much. Hide glue and epoxy require a discernible bond line of approx .005". Clamp it too hard and the glue extrudes out and starves the joint, weakening the bond. PVA and polys love clamp pressure. In fact, they don't work well without it.

In my shop, hot hide is more readily accessible, and easier to clean up. In case furniture builds, hot hide glue rub joints make small low strength assemblies go together like lego bricks- instant hold, often instant (but gentle) handling. For long joints in case sides, tables etc, I exclusively use PVA and a lot of clamps. Like hide glue, I find it easy to clean off of finished surfaces.

[jlanciani]

Lee Valley GF 2002 PVA. 45-60 minutes in clamps, over night to fully cure. Easy to use, decent open time, and since it has wood fibers it doesn’t seem to creep nearly as much as any of the TB PVAs.

[Hank Knight]

The thing that makes the biggest difference for me is good strong clamps and a well fitting edges when I'm doing flat panel glue-ups.  The glue is secondary unless some crazy grained wood is used.  Then the cold flow of the PVA glues can show joint slip over time.

I agree with Bob. This is especially true if the joint is not well fitted and must be forced into submission. This builds stress into the joint and, over time, the joint will move (creep) with PVA glue.

I've been using hide (both hot and liquid) for a long time and have not had this problem. I do, however strive for a well fitted joint to minimize stress. If I have to crank down hard on the clamps to get the joint to close, I go back to the chisels and planes. I had an interesting discussion with Adam Cherubini in Philip 1231's current thread over on the Hand Tools board about preparing a long joint for gluing up a table top or similar panel. Here's the link:

https://www.forums.woodnet.net/showthrea...83&page=13

There is a good general discussion about this topic that preceded my discussion with Adam.

[camp10]

Did you watch this glue test?   The Titebonds and Elmers wood glues did well.

But the thing that stuck out was the really good endgrain to endgrain perforance.  Have we been wrong all along on gluing endgrain?

[KC]

Did you watch this glue test?   The Titebonds and Elmers wood glues did well.

But the thing that stuck out was the really good endgrain to endgrain perforance.  Have we been wrong all along on gluing endgrain?

I take almost all these demonstrations/test with a grain of salt.  I've been butchering wood for 40 years, give or take.   I've glued joints that clearly could've been machined better, and at times have severely 'over clamped' to compensate.  I NEVER wet anything using Gorilla glue because my use has proven (to me) that it's not necessary.  What I've learned it we do what works for us... be it what glue to use and when, how long to wait before machining something that's been clamped, whether or not we think biscuits are good for anything,  whether loose tenons are better than a traditional mortise and tenon, etc etc etc.

[MarkSLSmith]

Lee Valley GF 2002 PVA. 45-60 minutes in clamps, over night to fully cure. Easy to use, decent open time, and since it has wood fibers it doesn’t seem to creep nearly as much as any of the TB PVAs.

+1.  I have also become a fan of this glue.  I would add it also has a pretty good shelf life.

Mark

[Handplanesandmore]

Tom, I agree with you that for PVA, 30 mins is more than enough for clamps to come out of any assembly (unless the shop is too cold). And that's a fact. In fact, a well cut dovetail joint can be held together with glue only and no clamps. Wood swells in response to wet glue.

By the way, observations are facts too unless proven otherwise. They are not necessarily just opinions.

Simon