Official Luthiers Forum!

A while ago I asked about glues to use for making up binding sheets with the side purling glued on. I picked up some Gorilla Glue to try out in the vacuum press and it seems to have worked pretty good, though I've not tried bending it yet. I'm wondering how builders speed PU glue over large flat surfaces. I started with a brush, but quickly changed to spreading it out with a single edge razor blade. What other ways of spreading work? Also, my little past experience with PU glue is that it has a short shift life. That can make it expensive to use. I use freezing for extending HHG and cyano, and refrigeration for epoxy. I have not been able to get cyano to actually freeze, but pints of it seem to last forever in the freezer. Does refrigeration of PU extend it's life too? Thanks for the input.--Bob

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“ The meaning of life is to find your gift and the purpose of life is to give it away” Pablo Picasso

Roller, or a larger notched spreader can help.

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

FWIW the super glues lasts for at least 3-4 yrs in my fridge . But the flow is not as good in winter here , shop is 65 deg F. The back of the white PU glue states it needs moisture, in tiny print . I had no trouble using it in our garage to glue up coco. at 55 deg F and around 35 % moisture. I have a small rubber veneer brayer for rolling out glues , a rubber J roller, and a 3 in clear art supply style roller for doing epoxies or Titebond, fish etc. Clean rollers with appropriate cleaner e.g. titebond gets vinegar soloution from the dollar store. Epoxy can be cleaned with acetone from dollar store . fish glue hot water and soap from dollar store , or apply your epoxy with a rubber squeegee DIY or from a dollar store as well. Beau hannam did a brief video on youtube showing his squeegee technique applying epoxy to a uke .

I/ve never tried to refregerate PU , this is my first time using it, it seems way to thick to put in a fridge at 40 deg F. I/m assuming it would flow vy slowly until warmed to room temp. The best way to find out is to test it yourself. since my work area is always between 65 to 76 deg F . I don/t plan to refregerate it . I find it also has a lot of other handy shop uses like making 2 black rubber squeegees from 1 used one , filling the gap in a wood wood handled clamp that is loose etc etc . It would seem that a dry fridge at 40 deg might extend the Life of the PU , but one would have to wait till it achieved room temp to use.

PU glue reacts with moisture to cure.

So if you can eliminate all moisture from it's environment... but that might be difficult living in Hawaii

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I'm not a luthier.
I'm just a guy who builds guitars in his basement.
It's better than playing golf.

Thanks for all the replies. PU is messy stuff. The notched spreader might be the best solution, being easiest to clean. Since I don't use too much of this stuff, the shelf life problem might be best solved by buying the higher priced small bottles which could actually end up being the cheapest route to take,

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“ The meaning of life is to find your gift and the purpose of life is to give it away” Pablo Picasso

FWIW bob I bought the small bottle of gorilla PU

I haven't used PU glue in a while because I didn't really like working with all that much. I also only had a few things that I felt like it was the right glue for and I ended up needing to buy a fresh bottle every time I needed some. If I remember correctly, you clean up with alcohol before it cures (nothing will touch it after it cures) that was the only way to keep it from staining my skin brown if I got it on me. I also remember reading an old post from Mario Proloux about PU. I could be remembering this wrong so don't quote me; he didn't feel like the gorilla brand PU was the best available PU because it foamed too much. He preferred the Elmer's brand PU. I think it was probond or something like that, they changed the name a number of years ago.

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Bryan Bear PMoMC

Take care of your feet, and your feet will take care of you.

So, the vacuum glue up of multi colored fiber purling sheets onto curly koa binding sheets went well. Gorilla glue was not all that messy once I figured out the procedure. I used a fiberglass spreader, thinned at the front edge on the sander and notched a little on the bandsaw. Worked great. An unplanned issue did arise when cutting the binding strips. I do that on the table saw with a narrow carbide blade and a zero clearance throat.I never have any issues cutting the strips with real wood purflings. Thinking the fiber purflings might peel off if I cut the strips with the fiber face down, I cut the strips with the fiber face up. Even with a new blade the fiber did not want to cut cleanly. It curled slightly at the edge of each cut. I was able to sand the curled edge and make the strips useable, however I need to figure out the cutting next time. Generally I use new disposable Ace Hardware 7 1/4" carbide ripping blades for this process. I don't know at this point if the problem had anything to do with the glue, or the kind of fiber, or the blade or what.

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“ The meaning of life is to find your gift and the purpose of life is to give it away” Pablo Picasso

When I was building cabs, I learned about Loctite PL Premium Polyurethane Construction Adhesive.
http://www.loctiteproducts.com/p/pl_ca_ ... hesive.htm

For the size of the tube, its actually very cheap to use. So much so, I ended up buying the "LARGE" tube, which was a workout with the "LARGE" caulk gun (that was a one shot deal - used the normal size after that).
As with most caulk gun based products, it'll harden in the tip, but is usable for a long while.
Dry time is insanely long, overnight at least, 48 hours till hard enough to cut, but it doesn't foam, at all. I used this when I redid my jigs.

"Even with a new blade the fiber did not want to cut cleanly. It curled slightly at the edge of each cut. I was able to sand the curled edge and make the strips useable, however I need to figure out the cutting next time. Generally I use new disposable Ace Hardware 7 1/4" carbide ripping blades for this process. I don't know at this point if the problem had anything to do with the glue, or the kind of fiber, or the blade or what."

One thing you could try is putting a piece of sacrificial scrap on top of the layup to hold the fiber down in place when cutting. An ATB (alternate top bevel) crosscut blade- might- also help.

I spread gorilla glue with dummy credit cards (those promotional ones that aarp sends me practically monthly). They work great as a glue spreader.

I spread the gorilla glue on one side, and then very lightly mist the opposite side of a glue joint. The moisture activates the PU glue and creates the magic foam that lets you know it is working. Clamp it tightly between boards, between plastic tarp pieces to keep from gluing your binding stock to the boards. This holds up great for the side purfling attachement to the binding. Then cut the binding pieces out with the veneer side up on the bandsaw and the veneers do not get pulled off the binding. Make your binding stock a bit too tall, so there is some meat on the binding left to level to the top/back in case of some roughness on the outer surface of the binding from the bandsaw.