glue for bent laminations

Tony Falotico said:

Barry, I've never tried Gorilla Glue because, what I've heard, is that it expands while curing, thus opening the joints.

Again, this is what I've been told by others and read in books (mags)...... so I never tried it.

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Tony, I use gorilla because of the concerns you mention. With loose joints and worn joints it is a great fix for old furniture repairs. Th expansion of the foam works into cracks and fills open areas. But it does require clamping to keep from pushing the joint apart. (just remember to NOT put any on the ends of Tenons and Dowels so it can't "Push out")

As for the mess, It is a matter of learning to be cautious of the spillage and to use small amounts of glue on one portion of the joint and moisture on the other to start the chemical reaction and the hardening process. (I wear Nitrile gloves)

As for Laminations with Poly glue, the working time is a plus and if you apply the glue to only one side of each laminating piece they will wait for you to finish applying to all the pieces. Spray a fine mist of clear water on the other side, just as you assemble the plys and clamp into the form. I like to use Wax Paper when I use Poly glue as it will not adhere and it protects the surrounding surface from the ooze of the foam during curing time. I keep any poly glued pieces in the clamps until the foam is hard and brittle, that way I know the process is completed.

I've had lamination failures with poly glue, two brands as I recall. It's not the 'foce things apart' problem, I just don't think they're REALLY strong in that application. I don't trust them for that anymore, and use only plastic resin. I still use Gorilla for all non-through mortise and tenon joints.

KC

i use all three kinds mentioned for bent laminations sucessfully.....i reserve urea-formaldihide for structural or waterproof aplications.....monkey glue is used when the temperature is below 40 deg. or so, and yellow glue 90% of the time.....all of my laminations are done in a vacuum so achieving good clamp pressure isn`t an issue.......tod

Bill Simpson said:

Tony, I use gorilla because of the concerns you mention. With loose joints and worn joints it is a great fix for old furniture repairs. Th expansion of the foam works into cracks and fills open areas. But it does require clamping to keep from pushing the joint apart. (just remember to NOT put any on the ends of Tenons and Dowels so it can't "Push out")
...

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I believe Polyurethane glue can be managed by use of the right quantity (very little) and proper clamping. BUT the expansion foam has almost no strength. The only joint I have had fail was with Gorilla glue. (I won't admit that my joint may not have been perfect before the glue, but...)

Wood glue (PVA) requires a porous surface, so is practically useless for repairs where there can be a trace of previous glue or finish. Poly will glue stone, metal, glass, etc. as well as porous surfaces, so makes sense for repair of tight joints. It is also waterproof. Therefore if I want a poly glue I use PL Premium Poly Construction glue. Cheaper and less expansion than Gorilla glue.

If you need to fill gaps, the glue that explicitly retains strength with gap filling is epoxy.

I find poly glue easy to clean up - mineral spirits while it is still wet, and the foam cuts or sands easily when it is dry. But it does permanently discolor skin (no washing the color off), and it takes 5-7 days for new skin growth to replace the discolored skin. Reminds me of nitric acid stains from lab days.

Charlie Plesums said:

If you need to fill gaps, the glue that explicitly retains strength with gap filling is epoxy.

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If your life depends on it use two part expoxy. Twelve years ago I built a 11' dingy using West System Epoxy and many of the joints were not perfect due to all of the angles. Used in saltwater many days and never stored inside or covered. Two years ago Hurricane Charlie blew it over the top of two houses. I had runners on it so I hooked onto the toe ring and drug it up and down the street hauling loads of roof tile. No joint failures. Amazing!!!!!!