PVA/Polyurethane glues vs. PL Premium construction adhesive


I had a glue-up that was going to take some significant time (not to mention a few somewhat loose mortise and tenons) and some left-over PL Premium in a caulking tube, so I decided to test it out by gluing some maple blocks together (and one with a 1/8" gap)
The one with the gap had laughable strength, but the wood came apart before the joint did with the no-gap test...not much point in anything stronger than that.
Has anyone else dumped other glues for this stuff? it's dirt cheap, waterproof, gap-filling, wood-colored, sandable, gives you something like 30 minutes of reposition time, seems to hold some stain once sanded, and seems to be rated for "structural" load... at least one of my yellow glues specifically say that it's not (if you ever get yellow PVA wet, it turns to jelly, so maybe that's the showstopper for load-rating an adhesive... not very safe for holding up a house :-)
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I just started using that stuff when my local supplier of Liquid Nails ran out. I like it! It is great for outdoor stuff like utility furniture, or where you can glue where no one can see the squeeze out.
I have used it on interior trim as needed (like glueing a bent piece of trim on a bulged wall, including the scarf joint) and it holds really well.
Since it is also waterproof when dried, I have used it for tile repair instead of buying mastic, and have glued metal corners on bead board wainscot using the glue, taped in place for 24 hours. Works great!
Robert
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snipped-for-privacy@aol.com wrote:

Yeah, I forgot to mention the squeeze out... there is lots of it because it foams slightly. The good news is that it fills the gaps, and the clean-up seems easer that with PVA glues... no drips, and I just pare off the hardened foam glue with a sharp chisel - you can cut it like balsa wood.
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Funny, I experimented with this just two weeks ago. I had some Gorilla, some Nail Power (mfg. Henkel), and some PL Premium. They're all polyurethane glues for wood, the first two marketed for cabinetry stuff, the last as a construction adhesive. The first is about 2x the price of the second, and the second is about 10x the price of the third.
Couldn't help but wonder if there was a possibility that the PL could used as effectively as the first two in similar applications, so I did a test.
The first two have about twice the viscosity, which makes sense since PL is a construction adhesive, not a cabinet glue. The runnier viscosity is desirable for how I wanted to use it, however, so the first thing I did was read to see what I could thin it with. Nothing on the tube, but it did mention mineral spirits as a cleanup agent, so I thinned it with that, and it seemed to work. You don't need much, and you have to spend a minute to get it mixed.
I cut some scraps of pine then glued up and marked a couple of blocks for each glue.
After they dried (and all had the similar foaming cure), I put each one in a heavy vice and pounded at the seam.
They all held up admirably, all splits were in the wood not the glue line.
Hardly scientific, but enough to satisfy my curiosity. If I have a project that's not valuable, I wouldn't hesitate to use thinned PL premium. I think I'd pick it over yellow glue most of the time.
2 H
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--snip--

I'd be afraid to thin it. I usually go by smell, and it didn't smell like anything I've ever smelled before. I've been burned by the like smell test too, though:
I hold sandpaper on blocks with *rubber* cement so I can replace it easily, and my bottle was getting a little gummy and had some *contact* cement thinner handy... if you take a whiff of the two, they both smell like they'd make you high in a few seconds (qualitatively, they seemed similar enough) but they definitely don't mix... it turned the rubber cement into something new --- "chunky" rubber cement, for which I have yet to find a practical use.
Also, there's that spray foam stuff (i.e. "great stuff")... It's polyurethane too. It says to clean it up with acetone, as I recall. So, it's either two diferent solvent bases, or those were just the best alternatives their product testers could come up with that you can actually buy at the borg, implying that it's probably not the ideal thing to thin it with.
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Well they are intended for 2 different purposes. You could probably enter screws and or nails in the mix as they too fasten pieces of wood together. That said, the caulk construction adhesives tend to keep the wood pieces spread apart due in part to the viscosity of the adhesive. Polyurethane on the other hand can be squeezed/spread out quite thin and over the entire surface with out the mess that a construction adhesive would present if you wanted to cover the entire surface.
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That's true, PL Premium almost has a putty-like consistency. But I like that! It's probably partly due to the extremely high solids content, perhaps something like talc is used as a filler.
I can definitely see how separation could be a problem -- even under clamping pressure -- but I don't usually make too many joints where I could see this as being a problem (e.g. a lap joint)... mostly mortise and tenon joints, where the viscosity actually seems to be benificial.
My usual process is to caulk-out a huge wad of the stuff (since it's *dirt* cheap) and use popsicle sitcks to "butter" all the surfaces. After I slather it on the tenon, I can wave the stile around for 20 minutes (while I try and remember where it's supposed to go) and the glue stays put with zero drips.
With PL, I've never had to clean up all the dried glue drips off clamps, tables, floors, etc.
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