Speaking of gluing up...

Re: Speaking of gluing up...

Larry Williams

>Stephen,

What "technical publications" are you talking about?

Re: Speaking of gluing up...

MikeW

>What technical publications, Stephen?

While it is a recommended practice in older texts, what I have read for modern glues and practice is to avoid using toothing planes. Probably that Hoadley guy's fault...

fwiw, I typically do use a toothing plane on hard woods when veneering onto cross-banded cores. I don't think there is any gain on more porous woods.

For edge gluing I don't use a toothing plane. I do rough a surface with 120 grit paper if it is a very dense wood just prior to glue-up.

Take care, Mike

Mike and Stephen

Larry Williams

>I don't doubt the information is out there, but there's a lot of contradictory information and very little that actually pertains to any actual testing data. I keep reading about hide glue's gap filling capability but the hard data I find doesn't agree with that. One person even suggested joints be cut differently for hide glue and PVA glues. I'm just searching for definitive information on glue properties and would like to find more/better sources. Access to Stephen's technical journals might be a help.

Re: Mike and Stephen

MikeW

>Hi Larry--sorry for placing my response to Stephen under yours...it can get confusing doing that.

I mainly use the toothing plane for face veneers because of being taught, not because I believe it correct or a "superior" method. In fact, the disadvantage of preparing the substrate for veneer (or other surfaces) with a toothing plane is that it can actually weaken the surface bond if over-done. The "ridges" can separate from the surface. Which is one reason my toothing plane creates very, very shallow grooves.

I think it all boils down to tradition.

As for hide glue, I think the so-called gap-filling only applies to hot hide glue which sets quickly. Its quick setting combined with its viscosity will bridge some gap. But hide glue, which I do use and prefer, dries to such a hard state that it can be brittle. I've pulled apart too many failed, sloppy hide glue joints to think otherwise.

There is no substitute for well fitted joinery.

Take care, Mike

Re: Mike and Stephen

Denis Ch�nard, Orl�ans, Ont.

>The latest FWW has a glue strength article. I wouldn't see it as the "final answer", I'll rank it for now as "interesting".

I've bought toothing blades, why I don't know, I guess I had a "Hillary moment" at the time... :-)

DC

Re: Mike and Stephen

MikeW

>Hi Denis,

Now, toothed blades in a bench plane are a cat's meow for working down difficult woods. The couple I had when I had my metal bench planes, though, were more aggressive (wider/larger teeth) than the vintage woody I use for veneering.

Take care, Mike

Re: Speaking of gluing up...

Stephen Shepherd in the State of Deseret

>Handbook of Adhesive Technology 2nd Edition by A. Pizzi and K.L. Mittal, 2003.

Handbook of Adhesives by Irving Skeist, 1989.

These are probably two of the best. And all of the adhesive technology publications always include a section on hide glue.

There are a few others but they are on my old hard drive which I haven't access to at this moment.

Stephen

not according to Franklin & Borden.....

Bill Tindal, E.TN

>I have a number of technical manuals from Franklin Adhesives Company(Titebond) as well as Bordens(Elmers). None suggest roughing the surface for PVA and aliphatic (white and yellow) adhesives. Furthermore I have never seen it done in a furniture factory or anywhere else.

One typically gets 80+% wood failure on a long grain joint. What's to improve?

Adhesive questions are easy to answer. Test glue a lap joint. Cure and smash it apart. If you are getting 80+% wood failure all is well.

Re: Speaking of gluing up...

Stephen Shepherd in the State of Deseret

>Traditionally almost all veneer and substrate were toothed or keyed usually with a toothing or truing plane. A rasp will also work and I have a handled cabinet scraper with a toothed blade.

Gluing dissimilar such as bone, brass, ivory, silver wire inlay were not only toothed or keyed but the surfaces further etched with a fresh clove of garlic rubbed on the material.

The toothing or truing plane can also be used to handle particularly difficult woods such as curl and burl. Musical instrument makers know the value of a toothed blade.

Finely toothed or keyed edge joints not only create more surface area but the small valleys help reduce the possibility of a glue starved joint.

Liquid hide glue does not have great gap filling abilities unless they are thickened with a filler. Hot hide glue is a little better but can still use something to thicken. You can add up to 10% filler without reducing the adhesive properties of hide glue.

Stephen

Hi Mike

Denis Ch�nard, Orl�ans, Ont.

>You are probably right regarding the toothed blades, it's just that I have yet to encounter a situation where I can't get a smooth surface using the regular blades. Gotta spend more time in the shop, I guess :-)

I have a toothed blade for my Veritas BU planes and one for the scraper plane, they're still brand new...

Happy Father's Day!

DC

Re: Hi Mike

MikeW

>Happy Father's day to you and yours, Denis!

I agree. A smooth surface is fairly easy to attain using, well, smoothers and longer planes if they are set up for it.

But it is getting to thickness--taking heavier amounts off harder to plane areas--that the toothed blade works well. I look at the toothed blades like some use a mildly radiused jack for, removing wood that would otherwise tear out in the flattening process.

My toothed blades are gone now, except in my smoother-sized toothing plane. I may well look for another couple (one smoother-sized, one a Jr. Jack sized) at some point with coarser toothed blades for working surfaces which tear out. We'll see.

Take care, Mike

back to work...

Re: Mike and Stephen

Paul Kierstead

>One person even suggested joints be cut differently for hide glue and PVA glues.

I do know this: If you have a very tight M&T and try to use hide glue, it can be a major PITA. The same joint will still be a PITA using PVA, but not as much.

Re: Speaking of gluing up...

Dean Lapinel

>"Liquid hide glue does not have great gap filling abilities unless they are thickened with a filler. Hot hide glue is a little better but can still use something to thicken. You can add up to 10% filler without reducing the adhesive properties of hide glue."

This statement is not quite correct. Don't think of urea/salt as weakening the glue but having other potential detrimental effects (degradation with time as an example). The bond is not as much adhesion in the classic sense either. Bottom line though is you want a clean joint for bonding...not a roughed up surface.

Re: Speaking of gluing up...

Stephen Shepherd in the State of Deseret

>Dean,

You said the statment is not quite right but did not address the content of the statement.

You wrote: 'The bond is not as much adhesion in the classic sense either. Bottom line though is you want a clean joint for bonding...not a roughed up surface.'

What is the classic sense? Hydrogen bond? Covalent bond? Chemical bond? Mechanical bond?

And yes joints should be clean, roughing doesn't make them dirty, and I can't believe craftsmen for hundreds of years would keep doing the same thing if it didn't work.

Stephen

Re: Speaking of gluing up...

Bill Tindal, E.TN

>Prefaced by the fact that I know little about hide glue, the technical manuals for aliphatic (yellow) glue stress a smooth surface for gluing. For surfaces prepared by sawing they emphasize all sorts of sawing parameters that must be met so as to not roughen the surface. They go on to describe how a roughened surface will show failure of the wood fibers that have been roughened. I doubt the details of adhesion are different for aliphatic vs hide glue. Both must "wet" (in a surface tension context) the wood surface. So one might conclude that what is good for aliphatic is good for hide.

Furthermore, hide glue will bond to glass with a strength that exceeds the strength of glass (near 100% glass failure at the joint) and glass is the ultimate in smoothness.

.

But the proof is in the pudding. Test a smooth joint and determine % wood failure. If there is near complete wood failure from a smooth joint, roughening can only weaken the joint by weakening the fibers

Re: Speaking of gluing up...

Stephen Shepherd in the State of Deseret

>Bill,

You wrote: 'Furthermore, hide glue will bond to glass with a strength that exceeds the strength of glass (near 100% glass failure at the joint) and glass is the ultimate in smoothness.'

You of course are talking about glue chip glass. Prior to using hide glue (that is the only adhesive that works) the surface of the glass is etched or sandblasted to give the glue a key or tooth to grab and surface shatter the glass.

Stephen

Read

Dean Lapinel

>I think you need to do a little internet research on hide glue and edge joinery.

Apples and oranges...

John in New Mexico

>Though I agree with your main point Bill, I don't think you can meaningfully compare wood and glass in terms of gluing surface, since one is an amorphous solid and the other is cellular, permiable, pourous, and fiberous. That hide glue sticks to both says more about the glue than the materials themselves.

John

Re: Read

Stephen Shepherd in the State of Deseret

>I have done a little research over the last 6 years and my book on Hide Glue will be published this fall if all goes well. I have read ever major technical manual on adhesives, a good physical science library at a university is a place to find those terribly expensive volumnes.

Stephen

Question

Bill Tindal, E.TN

>Sounds like you have done the research to answer a question I have had for some time. Why would the preparation of a wood surface be different from say metal or glass?

To glue two pieces of metal together (or glass) a perfect smooth surface and an adhesive that will wet this surface is best. Is there something about wood or wood adhesives that require the adhesive to penetrate the wood structure to get a good bond? And if penetration is required, why is the porous structure of wood not sufficient to provide for penetration such that roughening would be beneficial?

Re: Read

Wiley Horne--So. Calif.

>Stephen,

Please let us know when the book comes out. I think I know where you're coming from on the types of chemical bonding, and how they relate to crosslinking, or lack of crosslinking, in glues. I'm very interested in the extent to which hide glue cross-links--bonds to itself--and under what conditions.

Thanks for mentioning the book.

Wiley

Answers?

Stephen Shepherd in the State of Deseret

>Bill,

First of all, I don't know why glue works! But then again neither does anyone else, still a mystery as to exactly why any glue works. Given that there is still a lot of information about how glue behaves.

You wrote: 'To glue two pieces of metal together (or glass) a perfect smooth surface and an adhesive that will wet this surface is best. Is there something about wood or wood adhesives that require the adhesive to penetrate the wood structure to get a good bond? And if penetration is required, why is the porous structure of wood not sufficient to provide for penetration such that roughening would be beneficial?'

When you are gluing two non porous materials together you get a hydrogen and chemical bond and somewhat of a mechanical bond, which can hold very well depending upon surface preparation, cleaning and etching. (The garlic trick works great-an aside during my research I now know the intimate details of the chemistry of the garlic).

With porous materials such as wood you get a mechanical bond that physically holds the materials together, together with the other types of adhesive bonding that takes place, chemical, covalent, hydrogen, etc. The pores do help somewhat but the glue may not penetrate the holes because of trapped air within the pores. Sizing the boards prior to gluing will help.

Toothing or keying the surface increases the surface area of the glue joint and provides a mechanical device for the glue to bond to. An added benefit is that it is more difficult to starve the joint by excessive clamp pressure.

Application of glue to both surfaces is required for hide glue and this insures that both surfaces are 'wet' (surface tension wet). Putting the pieces together then pulling them apart to check for coverage actually sets up a bit of a capacitance discharge and can attract dust to the joint, Loudon levels and such.

I hope that answers your questions.

Stephen

When monomers become polymers

Stephen Shepherd in the State of Deseret

>As the monomer strand of colligen begins to cool or dry out it forms a right hand twist (I think, could be left) and coils up. This is hide glues property of shrinkage.

Surfactants come into play in wetting, micelle functions together with the surface of the material being glued. Air dried wood glues better than kiln dried and hard machined surfaces can have surface case hardening that also effects the bonding properties of the adhesives. The chemistry of the wood can also contribute to chemical and hydrogen bonding.

It is a lot more than just sticky stuff sticking stuff together.

Stephen