Cold creep in modified PVA glues?

[Mark Daily]

What the heck is cold creep? Is my furniture going to fall apart?
I use Titebond II and III...

[John TenEyck]

What the heck is cold creep? Is my furniture going to fall apart?
I use Titebond II and III...

Cold creep is shear (displacement) of the glued surfaces at room temperature, and happens when the shear stress exceeds the creep strength of the glue. It's often seen with joints that go out of alignment with changes in seasonal expansion/contraction of pieces that are glued together, like in a tabletop, or parts made up from laminated pieces. Another case is in bent laminations that try to straighten out with time.

Your furniture is not likely to fall apart, but if it does it will do so slowly if cold creep is the problem. But don't take anything you made with TB glues in bent laminations out in the hot sun as Mark pointed out.

And for those using epoxy in exterior projects, as I often do, recognize that many of them including West Systems loose substantial strength at elevated temperature, similar to PVA glues.

John

[Mark Daily]

Cold creep is shear (displacement) of the glued surfaces at room temperature, and happens when the shear stress exceeds the creep strength of the glue. It's often seen with joints that go out of alignment with changes in seasonal expansion/contraction of pieces that are glued together, like in a tabletop, or parts made up from laminated pieces. Another case is in bent laminations that try to straighten out with time.

Your furniture is not likely to fall apart, but if it does it will do so slowly if cold creep is the problem. But don't take anything you made with TB glues in bent laminations out in the hot sun as Mark pointed out.

And for those using epoxy in exterior projects, as I often do, recognize that many of them including West Systems loose substantial strength at elevated temperature, similar to PVA glues.

John

Thanks John, don’t know why I’ve never heard of this. I thought these things were due to expansion/contraction of the wood itself.

Just ran across this article: http://brownellfurniture.com/factors...n-woodworking/

Will longer clamping times reduce the amount of creep?

[John TenEyck]

Thanks John, don’t know why I’ve never heard of this. I thought these things were due to expansion/contraction of the wood itself.

Just ran across this article: http://brownellfurniture.com/factors...n-woodworking/

Will longer clamping times reduce the amount of creep?

Leaving the joints clamped long enough to assure the glue has dried sufficiently is always a good idea but it won't prevent creep afterwards. It's an inherent property of the glue itself. If you want to minimize creep use a glue with better creep resistance.

John

[Tony Zona]

What, pray tell, is PU?

Why do we have to use acronyms? It makes reading posts so difficult sometimes. And who wants to have to search anywhere to figure out what somebody said?

I know as soon as somebody says what PU means I’ll say, “Aha, I should have guessed that."

But right now what is PU, please? Have mercy.

[Phil Mueller]

PU: polyurethane glue...best known is Gorilla Glue.

[Tony Zona]

Thank you.

[Andrew Seemann]

So let's keep this in perspective folks, the "creep" that a glue like titebond 1 exhibits has almost no detrimental effect on most of the woodworking that most folks here do. It says not to use it for structural applications, but that refers to something like laminating roof beams for a hockey arena, not the structure of an entertainment center. Yes, it does creep a little between wood with different grain orientation, but that is probably more helpful than not given the other option is joint failure or cracked wood. When you add in the low toxicity, low cost, and ease of use, it makes sense that it is as popular as it is (and that is from someone who had a hide-glue-snob phase).

Stringed instrument makers encounter forces much higher than most case good woodworkers, and though there is raging debate amongst makers about glue, most instrument makers when cornered, will say that the instruments they made in their early days with titebond have held up just fine.

[Brian Holcombe]

I agree with Andrew.

[Mike Henderson]

So let's keep this in perspective folks, the "creep" that a glue like titebond 1 exhibits has almost no detrimental effect on most of the woodworking that most folks here do. It says not to use it for structural applications, but that refers to something like laminating roof beams for a hockey arena, not the structure of an entertainment center. Yes, it does creep a little between wood with different grain orientation, but that is probably more helpful than not given the other option is joint failure or cracked wood. When you add in the low toxicity, low cost, and ease of use, it makes sense that it is as popular as it is (and that is from someone who had a hide-glue-snob phase).

Stringed instrument makers encounter forces much higher than most case good woodworkers, and though there is raging debate amongst makers about glue, most instrument makers when cornered, will say that the instruments they made in their early days with titebond have held up just fine.

I've made quite a few laminated parts for projects, including rockers for several rocking chairs, using Titebond glue and none of them show any "creep".

During one of my visits to Sam Maloof, I asked Sam what he used for the laminations for his rockers (the actual "skates" or rockers). He pointed to a shelf with several bottles of Titebond glue, from Titebond I to Titebond III and said, "I choose which one to use by the color of the wood."

Mike

[Frank Pratt]

I've made quite a few laminated parts for projects, including rockers for several rocking chairs, using Titebond glue and none of them show any "creep".

During one of my visits to Sam Maloof, I asked Sam what he used for the laminations for his rockers (the actual "skates" or rockers). He pointed to a shelf with several bottles of Titebond glue, from Titebond I to Titebond III and said, "I choose which one to use by the color of the wood."

Mike

Well, if it's good enough for Sam...

[Brian Holcombe]

I think creep also must be affected by design and accuracy of fit ups.

I have a table in front of me that has been in direct sunlight hours a day, made with Titebond III that shows nothing of creep or even much of a seam at all. Of course the tenons are flush twice a year. This table is about 5 years old now.

[Mark Bolton]

I think creep also must be affected by design and accuracy of fit ups.

There is no thinking about that one. Thats plainly obvious. But in a lot of day to day work there is no time/profit in buddhist monk style fitup, grain/board/material selection, highly detailed fitment (doesnt mean your a slob), and so on. And it makes you look to options that allow you to move fast, make a quality product, with perfectly acceptable fitment, and take a few weeks of vacation over the course of the year that isnt funded by a spouses salary and health care.

Who would care if you could feel a fingernail of creep in a Maloof inspired rocker or seat for that matter that is against the floor and will likely never see the touch of a hand other than the cleaning staff who wipes down the hardwoods on their sweep through of your $3K rocking chairs? But when youre making reasonably every-day work and you have a supposed bread and butter adhesive that creeps to the point of being noticeable or even worse breaking the finish with reasonably modest production methods, it gives you a bit of pause.

I have personally never had a creep problem with TB Original or Super and that's what I stick with for interior day to day work.

[John TenEyck]

[QUOTE=Brian Holcombe;2951151]I think creep also must be affected by design and accuracy of fit ups.

I have a table in front of me that has been in direct sunlight hours a day, made with Titebond III that shows nothing of creep or even much of a seam at all. Of course the tenons are flush twice a year. This table is about 5 years old now.



Whether or not creep happens is very much affected by design. Maloof's rockers didn't exhibit creep because the laminations he used were thin enough that the stress was lower than the creep strength of the glue he used. But whether or not he started out with thicker laminations, had problems, and moved to thinner ones or just got lucky to start with is unknown to me. Most folks are familiar with spring back with bent laminations. That happens when the shear stress on the glue joints exceeds its creep strength. Switching to a glue with higher creep strength will yield lower or no spring back. This is where UF and epoxy glues excel. Maloof either through trial and error or luck ended up with laminations that kept the shear stress of the laminations in his rockers belong the creep strength of TBIII.

Similarly, your table shows no creep for the same reason, only more so. Where is the stress? Being in the sun doesn't increase the stress. It only lowers the creep strength of PVA and other thermoplastic glues. Unless you racked the joinery during glue-up there's essentially no stress on the joints in your table. But build an exterior door with TBIII, especially with wide panels glued up from several boards, and put it facing South or West with direct sun exposure. I think you will be disappointed.

For most interior applications you can use pretty much any glue you want. It's only when you add temperature and/or stress that creep strength becomes important; bent laminations, joints and panels under stress at elevated temperature, extreme temperature during shipping, etc.

John

[Mark Bolton]

Why do we have to use acronyms?

Unfortunately there is an acronym in the subject line... sorry ;-) They are everywhere and its simply faster and easier than typing out urea formaldehyde to type UF in an adhesive thread. Or some may just reference it as Unibond? Same with PVA and Polyvinyl Acetate, or CA and CyanoAcrylate. Or are we suppose to type PU-Polyurethane-(glue not the finish)-Gorilla Glue every time we reference PU?

Its life. Searching is good. You find lots of other information along the way.

It'll be ok ;-)