Glue Creep - Was Bent Lamination

[Teamcasa]

Below is an interesting thread on glue creep. In furniture making or general woodworking I have never experienced glue creeping after the glue has set. Yet others (below) have or are concerned about it. Has anyone ever seen this situation (other than structural adhesives or severe heat/abuse)?

Dave

-- Dave said: Creep is what happens to the wood sandwich as clamping pressures are applied. Blue tape will hold it most of the time for flat stock glue ups, it has a hard time when the form includes a bend and twist. Unless your bending form incorporates a twist as well as a bend, you should not have a problem with creep. If you do, and blue tape will not hold, (try it without glue first) apply clamps and cauls to prevent severe creep. Use clear packing tape on the cauls to prevent the adhesive from sticking to it.

Alex said: Okay. That's not my understanding of the term. I think it refers to a property of the cured glue line. From an engineering dictionary: :Creep - the dimensional change with time of a material under load. and from the Franklin Global web site: What is creep in an adhesive bond? Creep or cold-flow in an adhesive bond is the deformation of the bond line under a stress or load over a period of time

Dave said: Alex, I don't think that applies to furniture making. Structural materials, subject to significant pressures and/or vibration and large temperature fluctuations, maybe. If you are making a glue lamination beam (GLB), that may have to hold during a fire, then I'd worry about that type of creep.

Andy said: The most common sense of "glue creep" in woodworking is pretty much Alex's, but perhaps with 'time' replacing 'load'. Concretely, it's the phenomenon of having two pieces glued together become non-flush with one another at the glue line. Most common with white and yellow glues.

[Tim W]

PVA Glue never sets hard, it remains slightly gooey when dry and allows a little creeping. This can be good or bad. I have seen it many times.

If you glue up boards edge to edge to make a table top with PVA and you want a fine finish you will never with any amount of sanding be able to make the glue line disappear, because the movement of the wood will perpetually cause creeping in the joint. It is very slight but quite visible with a fine finish. The best glue for that kind of application is therefore one which sets hard like a rock like Cascamite. If you want to joint across the grain then creeping can be a distinct advantage because it allows a little movement without the joint breaking or the wood splitting.

Tim W

[Swingman]

I see ("feel" may be a better word, as it often hard to see) it to some extent on the occasional glue joint after a period of time, most noticeable on glued up panels during normal rh/temp changes.

Keep in mind that some woods, or cuts, may expand in thickness more than they do across the grain. QSWO seems to one of these where the phenomenon can often be seen, particularly when using thicker stock than the normal

3/4.

[George E. Cawthon]

White glue exhibits creep with higher temperatures. Never seen creep with a yellow glue (carpenters) and I have made pieces that creep would be obvious. Also, I have never seen a mention of creep, except with white glue, in a table of glues and their properties.

[Andrew Barss]

Here's a column discxussing various senses of "glue creep", and various glues:

[B A R R Y]

Swingman wrote: this situation (other than structural adhesives or

I wonder if the thickness of the glue joint matters?

For instance, if the joint is an ultra-thin, smooth, edge-to-edge vs. a rougher surface to rougher surface interface. While both would look great, the rough surfaces would use more glue and potentially allow more crrep?

[Teamcasa]

From Franklin

Thank you for your inquiry. A bent lamination is the type of application where our wood glues would most likely creep. Creep generally occurs where the glue line is under a permanent stress. Some of our wood glues provide a harder glue line when dry and would be less likely to creep. The wood glues that provide good creep resistance are Titebond Liquid Hide Glue, Titebond Extend Wood Glue and Titebond Polyurethane Glue. Titebond III is not a product that is considered to have good creep resistance. The amount of success using Titebond III for a bent lamination will depend on the thickness of the material and the degree of the bend. It is a good idea to allow the wood glue to reach full strength before releasing from the clamps when doing a bent lamination. I normally recommend clamping bent laminations for at least 24 hours. The actual clamp time will depend on the type of wood, moisture content of the wood, numbers of layers of wood and conditions in the shop. All these factors will affect the drying time for the glue. I hope this information is helpful to you.

Sincerely,

Marc Bergdahl Technical Specialist Franklin International

Posted Via Usenet.com Premium Usenet Newsgroup Services

---------------------------------------------------------- ** SPEED ** RETENTION ** COMPLETION ** ANONYMITY **

----------------------------------------------------------

[alexy]

Interesting. Thanks for creating a new thread for this, Dave. The context in which I have seen the discussion most is in the recommendation of plastic resin (urea formaldehyde) glue for bent laminations, in which sheer forces ARE significant, and there is no mechanical joint to keep the joint from moving if the glue allows creep.

When I get a chance, I will run a test with laminations glued with different glues, to see what kind of results I get. Will report back here.

[B A R R Y]

EXCELLENT info!

Thanks for taking the time to put the question to Franklin and sharing it with the rest of us.

[Ron Magen]

Alexy,

Most tillers are made from 10 plus one-eighth inch thick pieces of Mahogany and Ash laminated together. The adhesive used is epoxy {with the proper 'fillers' to have it act as a glue}. The final touches are cut or carved, and the finish is {SHOULD be} 6 & up coats of 'short-oil' UV varnish.

The handling, being banged about, and 24/7 exposure to weather {in more cases then not}is probably the harshest treatment for such a structure

I have heard of tillers have been abused or even broken, but never by delaminating, or the surface appearance of 'glue creep'.

Regards & Good Luck, R>

infrequently.