Glue Technique

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Hi, All...
I was watching a good video on YouTube on woodworking, and the guy just glued one piece of a board before clamping. I use Titebond III and try to avoid end grain joints with tenons, rabits, or what ever. But I generally apply glue to BOTH pieces before clamping. For example, gluing up 3 six inch boards to make an 18 inch panel, 3/4 inch final thickness: Glue to all edges, then clamp.
So, What is the concensus for putting glue on one piece, or both? Is there a risk of glue starvation on an otherwise snug joint?
Thanks for any comments. Rich.....
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On Mon, 5 Jan 2009 12:19:08 -0800 (PST), snipped-for-privacy@yahoo.com wrote:

I put glue on both mating surfaces, as recommended by the manufacturer. But there are some glues that should only be applied to one surface. Based on experience, I can get very close to limit the amount of squeeze-out. In my earlier days glue dripped all over the place. Like global warming, I don't believe "glue starvation" is an issue and never heard glue manufacturers address it.
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snipped-for-privacy@yahoo.com wrote:

Both surfaces. Always. Ever brush glue onto a surface over a large area then come back to where you started and see all the places you missed or where it didn't get into the pores? I'd imagine the same thing would be true of the unglued piece inside the joint that you can't see once you've put them together.
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In 30 years I cannot remember a time when I applied regular wood working glue to both sides unless end grain in involved. You really don't want to glue both pieces if one is a veneer. I have never had a joint fail because I did not put glue on both sides. Really, the glue gets on both sides when you put them together. If you have a good tight joint to start with there will be no starvation.
That said, if you glue both sides you do have more open time on a complicated glue up.
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The conventional wisdom is to wet both sides with glue. I think the reasoning is partial skinning, with yellow PVA especially, prevents full wetting of the mating face. It's easy enough to check. Stick two faces together and then pull them apart and see if both faces are fully wetted. There were distinct dry patches when I did this even, with an excess of glue. What does it mean? I guess most joints are over-designed in regards glue surface to begin with.

Which is made up for by requiring more time to spread glue on the other side. I do wish it were so, though. I'm tired of rushing the glue up to get them into clamps soon enough.
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Yeah but if the glue skims over, it does so on both pieces does skimmed over glue stick well to skimmed over glue? ;!)

With lots of practice you eventually learn to get the glue out spread quickly qirh out muxh fuss. I remember a time when glue up required lots of set up time. Not so much any more. I probably should have qualified my statement more. If glueing end grain I tyically apply glue to the end gran and let the soaking in start up, glue the mating surface and then rewet the end grain side and then clamp.
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I wrote unclearly. By the time you're done painting up the one side, part of it will have already skinned over. If you glue only one face, leaving the other face dry, that joint will be skinned glue on bare wood, and probably compromised. Skinned glue on skinned glue is the normal case, I think, and perfectly OK.

Might be that my view is skewed from using glue that seems half dried from the start. The low humidity isn't helping, either.
A coupla weeks ago, I did a simple box shape, 4 sides and a ply sheet, 16 biscuits in all, that had to come together as one glue up. The glue was some old yellow Elmers I had left over from last century, and skins over almost as it's leaving the bottle. I'm thinking of chucking the remaining half gallon and just get simple white glue. Fuhget about Titebond dis or dat, and watertight nuthin. I just want the glue to still be glue when I stick the pieces together. It was a hectic footrace, and I had 12 of them to do. The last few weren't any more fun than the first few.
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Snip

Climate certainly has an effect on the glue.

As the old saying goes, glue is cheap compared to your time an other materials. Get rid of your old glue. I keep several glues on hand and mostly for color. TB II IMHO has a pretty long open time for a regular wood glue but tends to be runny and a bit messy and you need very good fitting joints to hide the yellow. The old Elmer's Tite Bond had a fast tack but fried closer to white. TB III seems a bit thicker and dries to an actual medium brown wood color. Recently I have used Gorilla WHITE PVA Woodworkers glue because it is white and does not dry with a distracting color, this was for a maple project. Also TB Trim Adhesive is white and dries to a non yellow color however it dries a bit more quickly and is very thick, IIRC it will not pour out of the bottle, you have to squeeze the bottle to dispense. Then there is the slow set TB glue for longer open times. I buy poly urethane as needed, it's expensive, has a short shelf life, and is really messy if you are not careful.
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On Mon, 5 Jan 2009 20:37:38 -0600, "Leon"

I've never had a "skim over," but I plan a glue up carefully to get the piece assembled quickly. Glue brushes, glue roller, unused credit card, and finger is what I use to spread glue quickly. Clamps, jigs, damp rag are nearby. Dryfitting everything speeds everything up and if the item is complex, I'll glue up part of it.
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It's funny (and fun) how we get so caught up with simple things.
Musicians do the same thing. A drummer friend of mine once said, "We have a tendency to make rocket science out of hitting things with sticks."
:-)
--

-MIKE-

"Playing is not something I do at night, it's my function in life"
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[...snip...]

[...snip...]
Also simple surface tension; even if you are fast enough to avoid skinning, you still have to physically break through the "skin" that any liquid will have on the surface.
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What is this skin you speak of? :-)
Seriously, is I take a little extra time with a glueup, I end up with higher viscosity glue not "skin".
Are you woodworking in the desert?
-Steve
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StephenM wrote:

With most common woodworking glues - yellow, white - the glue dries from the outside in. If you put a drop somewhere it will form a skin...push on it and fresh, unskinned glue gushes forth.
Yours is probably "higher viscosity" because it is a thin layer and the higher viscosity is because it has skinned. Higher viscosity/skinned is not good because it won't wet out the wood as it should.
--

dadiOH
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"skin" could be defined as viscosity gradiant. In my experience, I do not notice any gradiant, just thicker glue.
Then again, maybe I just work quickly. If I don't think I can get an assembly together within 10 minutes, I try to find a way to get it done with sub-assemblies.
The OP initially asked (paraphrased) Gluing, one side or two? More often than not my glued surface stays open to the air for less than 2 minutes ... viscosity/skin seldom comes into play. It would probably be fair to say that gluing both sides buys wou a little more working time if you need it.
-Steve
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StephenM wrote:

He mentioned surface tension. Even pure water has a skin in that sense--some critters even use it to move about (google "water strider" for one example).
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Trimmed for brevity...
>>> you still have to physically break through the "skin"

I conceed that I did not address the surface tension interpretation of "skin".
I believe that assembling a joint would provide sufficient force to overcome surface tension a.k.a. hydrostatic pressure.
-Steve
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The other half of that thought is if there's anything under that skin to squeeze out, it's more squeeze out than I like. Normally, I run a squiggle down each edge, and smear 'em to flat films with my finger. Each face is fully wetted, leaving very little that can squeeze out. I suppose if I put the same amount of glue, the same amount as for both edges, onto just the first edge, there should be enough to squeeze out. I dunno. I guess it could work, but just seems so hit or miss. You run a double size bead, and then smoosh it around blindly with the other piece. Too small of a bead means not enough glue; too much means lots of cleanup. As it is, I inevitably have to wipe some extra off my finger, or move some of the extra to a slight dry area. It could work. Just put on a double size squiggly bead, smoosh the two across each other for half the squiggle distance, and come back a full squiggle distance. It could work. It just seems so... so... imprecise? caveman?
Come to think of it, that's not the real problem. Flat straight edges are fast and easy, either way you do it. It's buttering up the biscuits and feeding their holes, or painting up the M&T that takes up time. There's not enough sliding room to do the smooshing around with biscuits, and none at all with M&T. Do you just clamp and hope for the best?
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StephenM wrote:

Surface tension is not hydrostatic pressure. Surface tension is a molecular adhesion effect that occurs even in the absence of significant pressure.
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I understood hydrostatic pressure to the term for that molecular adhesion.
Thanks for setting me straight.
Steve
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snipped-for-privacy@yahoo.com wrote:

It depend on the type of glue being used. Directions for polyurethane adhesives, for example, suggest dampening one edge and applying the glue to the second edge.
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Jack Novak
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