Hey glue nerds

Titebond has a great technical help line

I resemble that remark

Ellis Walentine

Hi Paul,

I have little experience with PVA glue at high temps, but my guitar setup guy says he softens PVA with heat for guitar repairs. That would be the danger flag for me.

Regarding your question, I've had PVA gluelines creep over time in normal temperature ranges.

Bill Tindall is our Franklin expert. Maybe he'll chime in here. Or, as Dick suggests, try Franklin's tech support. They may have something designed specifically for this situation.

Ellis

Re: Hey glue nerds

Joe shelton

In his article on bending gunstocks, Bob Smalser says "...polyurethane and resourcinol glues are the only ones that will withstand the heat..."

But he wasn't talking about 300 degrees. His target heat started at 180 degrees. When I use his techniques, I sometimes get 200 degrees or slightly more.

Re: Hey glue nerds

JL

How about "Super Titebond"? The big drawback is that it comes in a 5 gallon (and 55 gallon) pail.

http://www.titebond.com/product/glues/0c432f73-dd8c-40de-8734-68eaf96f8e71

good luck

Bill Tindall, E.Tn.

You are going to need to do some researching to find any glue that remains mechanically and chemically sound at 300 degrees. Titebond regular will not only not be an adhesive at this temperature it may begin to decompose.

To help looking it will have to be a cross-linked glue. Probably some formulation of epoxy may work at this temperature.

What are you gluing that will survive 300 degrees, never mind the glue part? Stick a piece of wood in an oven at 300 and it will dry so fast it will crack.

J-B weld is good to 500º

Keith Newton

So,,, I would be interested to know what the project actually is. I hope you know you might get better advice when you give more specifics.

Otherwise I think resorcinol glue will withstand high temperature but I don't know its limits.

Question

Bill Tindall, E.Tn.

does the glue have to hold and bend at 300 degrees? Not possible.

The science behind it

Bill Tindall, E.Tn.

All adhesives are polymers when cured. Polymers are extremely long molecules. They have special properties, like being a good adhesive or plastic or finish, because these long molecules tangle up with one another like wads of long string or yarn. It is these tangled up molecules that result in toughness and other polymer properties. If the molecules are fastened together with chemical bonds the polymer is said to be "cross linked".

Melting is familiar to all. The material goes from solid to liquid at its melting point. Some polymers have a melting point, high density polyethylene, nylon or polyester for example. When melted the polymer goes from a hard glass-like material to one that is a viscous liquid.

But polymers have another temperature transition, called the "glass transition" temperature. At this temperature the polymer goes from a hard glassy state to one that is rubbery. The transition has to do with the polymer molecules becoming wiggly. Even though the stuff looks solid, the molecules are moving tiny amounts.

Above the glass transition temperature the material will deform/creep because at this temperature the molecules are wiggly and can adjust to force applied by wiggling to lessen the stress produced by this force(AKA creep).

It is rare to find a polymer with a glass transition temperature as high as 300 F. To keep polymer molecules from being wiggly and moving in response to stress at this temperature (creep) they will need to be highly cross-linked.

A hard glassy polymer whose glass transition temperature is above room temperature can be made rubbery (its glass transition temperature lowered below room temperature) by adding a plasticizer. PVC is hard brittle material. Add 30% plasticizer and the result is rubbery fishing "worms".

PET glass transition temperature is about 80C. Soda bottles are blown from PET above its glass transition temperature. Think blowing up a balloon and then freezing the shape by dropping the balloon shape below the glass transition temperature.

Put some water in an empty bottle, pop it in the microwave to boil the water. The boiling water at 100C will heat the PET above 80C . Now the molecules that were "frozen" in a stressed state can wiggle and relax. The bottle will shrink (creep) back to almost what it started out at before the bottle was blown. Children love this experiment.

Re: Question

Keith Newton

Bill, are you concerned about the glue itself crumbling, or the resistance of the veneer pulling on the glueline? When you consider that the standard veneers are only 1/50" (0.02") to 1/42" (0.024") thick, and at the heat level Paul mentions, at that temp, the lignin will be somewhat fluid won't it?

Having said that, if Paul is doing a marquetry two or three ply veneer that he wants to bend, I don't see any advantage for going over 210º F. But then I don't know what secret project he is not wanting anyone to know about. He may be stumbling along a path that others have discovered the stumbling blocks, and can warn him about that he doesn't even know to ask about yet.

Forgive me if I sound condescending, but a vague question may need a book chapter to cover all the possibilities that a more specific question may be answered with a simple yes or no.

Re: Question

Bill Tindall, E.Tn.

If the whole structure needs to bend at 300 degrees the glue holding it together has to bend. The stress on the glue or glue line could be substantial. The glue will either creep to relieve this stress or the glue line or glue may fracture if the glue is too rigid to creep and the stress is too great.

Brittle glue won't creep. Brittle glue may fracture under bending stress. Given the sparse information we can only guess.

Now I see you make guitars, so sides?

Keith Newton

OK, now if you want to know how I would do this, I can be more specific.

Rather than bending the sides around a hot pipe, I would make my Marquetry or Parquetry face up as a two ply using regular thickness veneer. If the second ply is across the grain of the bend it may be more flexible, but that may not be necessary unless you are using thick veneers.

Then, I would use epoxy for the adhesive in a vacuum bag with the form NOT IN THE BAG. If you have a two part form, at least for the thin waist, you can use it to push this into the inside main form first, then follow by bending the other halves around to hold it into place before you draw the vacuum. Jig form doesn't have to be so perfect since the bag provides perfectly even pressure from both sides.

I just pulled out a stack of 12 leaves of beech 6" x 8' long, that sagged to almost a tight enough bend for the hardest curve from it's own weight. So when doing a laminated bend, if you have to apply say 10# of pressure to press into shape, they are all working against each other, so there won't be any springback with that many plys.

Epoxy doesn't need a lot of clamp pressure, and lets the plys slip by one another like they've been greased while making the bend. Back in my early years using a quick tack water base glues, I had used up most of my open window of time just spreading glue, so had bunching up of the first few plys on the inside of bends that wouldn't slide. That isn't a problem with epoxy.

You may be thinking, but as a guitar maker, I require a certain density for the tonal quality. Well, Epoxy alone it very brittle, but it's the additives that allow you to control that somewhat with that, or using a different ratio of parts A & B.

And just because you may not have a vacuum pump and bag, I will share that my last bagging was a rather large project that I had to build on top of a 10' x 12' 6mill clear poly material that I sealed 3 sides by folding it over onto a heavy bead of butyl caulk. There was so much void in the parts that I got worried about my pump pulling fast enough, that I switched over to a small shop vac. I have done test with shop vacs, and all of mine, even the small ones pull -2psi, which is enough when using epoxy, so it saved my a$$ from loosing about $600 in materials.

Some people think that a vacuum cleaner is working harder by pulling against a blocked hose, but it's just the opposite. The motor screams by running at no-load speed. It works harder when it moves lots of air.

You can buy a box of clear 55 gal drum liners from Lowes for about $15, which will work for a bag, which puts bagging within anybody's reach.

Re: Hey glue nerds

Grant Smith

Dap weldwood high heat is about the most heat resistant glue I am aware of. I have used it for bonding laminated wooden water skis, and it is often used for the large arched glue-lams sometimes seen in churches and other large spaces.

Unsure of exactly what it can handle, but I am given to understand it is about top end of the options.

FWIW,

Re: I resemble that remark

TomD

Titebond 1 is the go to synthetic glue for guitars, as it has a track record in that use. As mentioned guitars can be repaired with either steam, or heat elements, that do about 400F. You can also use an iron which I don't think will get that hot.

I just heard the saga of how Rogers developed the kydex holster, and his biggest challenge was getting glue that would allow him to bond to leather, and would not come off when the kydex was heated to 350F. Nothing he tried worked until he used the stuff they retread tires with. Being in industry, he was able to try a lot of options.

Re: Now I see you make guitars, so sides?

TomD

Sounds like you are doing a KHSD multihull.

I love the shop vac approach, and have used it for 40 years, but it does not have the pressure required here.

Epoxy should not be adjusted for hardness by varying the mix. All that does is ensure is an incomplete cure and nasties in the mix.

Epoxies, the harder ones are not brittle. WEST got the boat market sewn up due to having free access to Dupont scientists through a friend. They made a hard epoxy. Most people who came after propagated this myth that the WEST was brittle, when it was optimized. Which is not to say the cheaper, or later products are bad. But the marketing is chancy in my opinion.

You want a hard glue for lutherie, which is why a lot of luthier say they have moved back to hide glue.

More info

Paul Woolson

Here is a sample of what I've done in the past. In the custom guitar world, I've become kind of know for doing these strange marquetry guitars.

I'll be laying up a marquetry pattern flat, then bending it as a side. My bender uses two heat blankets and I bend at 300°. It doesn't have to maintain that temperature for long 5-10 minutes.

I would like the glue to soften but not slip (that was what I was referring to as creep, not sure if that's right or not).

Happy to supply more information if it helps.

You have identified the requirement

Bill Tindall, E.Tn.

The glue can't be rigid or it will fracture upon bending, or if not it will act as a spring and pull the bend back toward straight. The glue must creep at 300F to relieve bending stress, but not too much. It can't be too rubbery or the pieces will slip out of alignment at 300 F. These are tall requirements. Doubtful anyone knows from experience or testing. You are going to have to do the testing.

To preserve viscosity at high temperature I think the adhesive will have to be crosslinked when cured. One of the hundreds of epoxy formulations may work. Try calling System 3. Maybe a crosslinked vinyl would work- Titebond II.

Thanks!

paul woolson

Thanks! I've done some side laminating in the past, but always with pre-bend sides. Am I understanding correctly that you are saying to lay the whole thing up flat with epoxy, in the bag, pull a vacuum, then bend the whole thing to the mold? I think that might work if I tack glue the pieces together with a dot of titebond.

On the argyle guitar (pic below) I glued everything up on a piece of posterboard. Then flooded with epoxy, sanded off the posterboard and epoxied to a piece of walnut and bent. That had decent success but not good enough to be very repeatable. I think I like your idea of bending cold and letting the glue do the work.

Re: More info

Bruce, a MN Galoot

If you will email me, I have a suggestion of where you can go to get some answers from a real inlay master, though not many people know much more than TomD when it comes to the intersection of guitars and epoxy.

Re: More info

paul woolson

I dont' see your email address

Mine is paul at woolsonsoundcraft dot com

If regular avenues don't satisfy..

David Weaver

...try an instrument supply place like LMI.

They have creep-free white glues and all kinds of stuff, and there's a whole lot of laminated bending with heat in the world of instruments.

Ellis's comments about white glue are true - the rumor that it is unrepairable is just that, a rumor. It just takes more steam and heat to get it to give up, but it will give up (plus, it's good policy to remove glue and get fresh wood when redoing a joint).

Not quite

Keith Newton

You ask,? .

No, if you pull the vacuum first, it will be too rigid to bend. You pull the vacuum after it is bent around the form. If there is plenty of epoxy in the joints, it will be so slippery, that sometimes it's hard to keep the stack aligned, but not so bad on a project this size.

As for the remark about playing with the mix, some brands just will NOT set. However the one I use will, and I have tested that, but not found a project where I wanted to do that. And the info came from the tech support chemist with that company. The nice thing about knowing this, is that it's not so sensitive about the mix ratio that being off a couple of % isn't going to keep it from setting like some others I've used. Back when I used one of the other brands, I might have pumped 12 pumps of the resin into a cup, then on a couple of strokes of the second part, a bubble gets drawn into the pump cylinder for a couple of strokes. What do you do then? Guess how much of a stroke was air and how much was part 2, or throw it away and start over. I have enough angst in my life without having to deal with that.

Invest in a scale

Bill Tindall, E.Tn.

I mix by weight. One can weigh to any accuracy required.

Re: More info

Don Stephan

My usual practice for complicated marquetry like that is to assemble the show face using blue tape on the glue side, cover the show side with veneer tape, remove the blue tape on glue side, and make up a 3 ply for more stability. The plies could be glued together against a form, but once cured a rigid glue likely would not allow the minor adjustments needed to fit the actual guitar body.

Re: Invest in a scale *LINK*

Keith Newton

Yes, but not as quick and easily as just sitting two clear solo cups of the same size side by side, then pouring the two parts in each until they are the same level, then mixing them together, especially since the brand I use isn't al that sensitive about the ratio. And as stringy viscous as this stuff is, a scale would end up so contaminated with unmixed epoxy it would be a mess before long in my shop.

What I do when I have lots to mix and spread is make a master cup with a medium sharpie line for both parts marked on the outside. The actual cup that will be used for mixing nest inside it. Then I or whomever I have mixing just pours in part 1 to the first line, then B to the second until it level with the second line. Then I lift out that cup and stir and add colloidal silica without messing up the master cup.

I don't bother with a roller tray, rather just pour from the mixing cup right onto the substrate ahead of the roller as I walk along. Then I come back rolling it out side to side from that first run. I can roll out and shuffle parts as fast as someone can mix pint size batches. This way I don't have to worry about it kicking from too much depth in the mixing pot.

Here is a link to the company I deal with, and I have no interest in the company in any way, just a happy customer. I think the price is about $75 per gallon, which is the size I normally buy now, but back when I was working on boats more, I bought 5 gallon pail size.


https://www.fgci.com/products/