Glue Failing?? chopping board, too much clamp force?

[JasonMcBride]

I have started making some chopping boards and some (a lot) of the glue joints seem to be failing. It is almost always when using merbau. I am wondering if I am using too much clamp force?
The merbau is old and weathered so I don't thing tannin is the problem. I have used the jointer to make sure the surfaces are flat. What am I doing wrong?
Cheers
Jason

[jack620]

Possibly too much clamping force. What glue are you using?

[JasonMcBride]

Titebond III

[jack620]

Titebond 3 is good stuff. If the wood is very dry it might be drawing the water out of the glue before it can cure properly. Have you tried applying it liberally to both surfaces?

[JasonMcBride]

Plenty of glue used

[The Spin Doctor]

I'm not familiar to the quirks of most Australian/southern hemisphere woods but two things to try.

If your gluing straight from a jointed surface, try a couple passes on each surface with some 60 or 80 grit. PVA glues need a surface that allows them to grab on with the billions of interlocked polymer stands or it'll fail. Apply the glue as usual and then run along with your finger, smoothing it out over the entire width of the joint, in both directions. If the wood is resistant to the absorption of the polymer strands in the glue, then ya, too much pressure will squeeze out the glue without allowing it to do what it's designed to do - so less pressure. Say, snug it up just enough to stop the boards slipping around as they do. Maybe an eighth turn more, but that's it. Titebond III has excellent gap filling qualities so there's no real worry about that, but you may have a more visible glue line.

[tonzeyd]

When you say glue is failing what exactly is happening?

A few questions:
- Do you know moisture content of wood?
- are you following general guidelines of wood construction ie no end grain to edge grain etc
- are you clamping within the open time?
- are you within the glues working temp? It's pretty cold ATM, are you doing glueups late at night? When the temps dip?
- how old is your glue? Have you tried gluing other bits of wood/ scrap merbau together does it hold?

A photo of failed joint might also help

[JasonMcBride]

When you say glue is failing what exactly is happening?

A few questions:
- Do you know moisture content of wood? Whilst I don't know exactly, I know that it is dry as it has been stored in a closed shed for a year, and it is old merbau (not green) that was sitting out in weather for 10+ years prior to that

- are you following general guidelines of wood construction ie no end grain to edge grain etc - Yep
- are you clamping within the open time? - Yep
- are you within the glues working temp? It's pretty cold ATM, are you doing glueups late at night? When the temps dip? Normally mid morning
- how old is your glue? New Have you tried gluing other bits of wood/ scrap merbau together does it hold? Other wood, (Vic Ash etc) seems to hold fine
I'm just wondering if either I am clamping too tigh and squeezing all the glue out and because merbau is so tight grain it doesn't get a chance to penetrate? Or maybe in this weather I should leave it longer than 24 hrs? (I'm in Melbourne)
A photo of failed joint might also help

Thanks

[cava]

I’m on the Mornington Peninsula and do not have any problem with glue ups.

I use old Merbau and Titebond 3.

I also put as much pressure on the joints using Bessey clamps as I can but I do not do any glue ups if the temperature is below ~16c and I also clamp for 48 hours.

I think temperature could be a factor in your problems. Can you bring the chopping boards inside overnight? Just a thought…

[JasonMcBride]

I also put as much pressure on the joints using Bessey clamps as I can but I do not do any glue ups if the temperature is below ~16c and I also clamp for 48 hours.

I think temperature could be a factor in your problems. Can you bring the chopping boards inside overnight? Just a thought…

Yeah, I might try that.

One other thing, I use pipe clamps, and when I tighten, the timber always tends to "creep up" off the pipes (even with one on top) do the Bessey clamps have this problem? I have a bugger of a time trying to keep the timber flat down on the clamps.

[cava]

Yeah, I might try that.

One other thing, I use pipe clamps, and when I tighten, the timber always tends to "creep up" off the pipes (even with one on top) do the Bessey clamps have this problem? I have a bugger of a time trying to keep the timber flat down on the clamps.

I still get glue creep, even with Bessey clamps, but most of the time it’s manageable.

[tonzeyd]

Clamping for longer than 24 hours won't make much of a difference.

The final thing i'd suggest is gluing up a scrap piece of merbau but before you glue up wipe it down with turps or similar. Let the thinner dry and proceed with glueup.

If it holds then its the oils in the timber causing the joint to fail, in which case i'd probably just get rid of the merbau is use something else.

[Camelot]

Yeah, I might try that.

One other thing, I use pipe clamps, and when I tighten, the timber always tends to "creep up" off the pipes (even with one on top) do the Bessey clamps have this problem? I have a bugger of a time trying to keep the timber flat down on the clamps.

Try putting salt along with the glue to help with the creep

[jack620]

"According to Jeff Loflin, glue specialist at Franklin International (maker of Titebond wood glues), salt (and sugar, too, by the way) can react with wood glue and alter its composition, resulting in a weakened joint."

Should I use salt in my glue to prevent slipping? | Wood

[mpot]

"According to Jeff Loflin, glue specialist at Franklin International (maker of Titebond wood glues), salt (and sugar, too, by the way) can react with wood glue and alter its composition, resulting in a weakened joint."

Should I use salt in my glue to prevent slipping? | Wood

What about a few grains of course sand, instead of salt? That would be less likely to react with the glue.