Epoxy glue joint opened

[Mark Gibney]

I glued up this oval Santos mahogany coffee table on Sunday.

Yesterday morning, Tuesday, I placed it outside under cloudy skies in the hope that the UV to hasten the darkening of wood surface before finishing later this week.

The center seam opened up. I used brand new T-88 epoxy with biscuits when gluing up this top.

I jointed the mating edges and wiped them down with acetone before applying the epoxy.

I've had this wood in my shop for many years, so it's beyond dry.
Any ideas why this happened?
Is the only solution to rip it apart and re-do?

518841 518842

The seam opened from end to end, but not on the underneath.

Gimme your wisdom! Mark

[John Kananis]

Mark, I can only think of 3 things.
1) Is the epoxy expired (although you just bought it)?
2) did you mix it well enough?
3) did you clamp too tightly and starve the joint?

[Jimmy Harris]

This happens sometimes. You could try to patch it with some kind of wood filler. It's not all the way through, so it's not structural. It's just a cosmetic problem. Or you could rip it and retry. It's a small enough gap that if you wanted to get crazy, you might inject some thinned out epoxy, wet the wood around the gap to swell it, and keep it wet while the epoxy hardens. But that's probably more trouble than it's worth, as it's probably easier to mess up than get right.

Or just leave it and fill in the gap with finish. You'll still see it, but if done right, you won't feel it. And you probably won't even see it if you don't know where to look.

[Larry Edgerton]

No finish on the wood? I do the same thing for color before finish but I flip it every 15 minutes or so. The one side is hot, the other cold and that will make it change slightly size even when dry. I agree its not bad enough to rip and reglue unless it will drive you crazy.

You probably already know this but epoxy is a mechanical bond and so requires something to grab on to. If the wood is hard/closed pore after machining I will rough up the glue surface. I usually use a ponse wheel if the wood is not super hard, a tiny drill bit if it is.

[John TenEyck]

Epoxy likes a rough, non oily surface and, as John said, a relatively thick glue line. Jointing the edge cleanly might not have given it anything to bite into. I've had a few joints with T-88 open up, too, on Sapele, but it took months of weathering to do it. A well fitted ripped edge might be better.

Dry is a relative term. Clearly the wood moved in response to moving it outside. Maybe the sun dried it on that side?

I don't see any alternative repair other than to rip and reglue.

John

[John Lanciani]

Rip and re-glue, anything else is a waste of time and effort and will show for the life of the piece. As mentioned above, most likely a starved joint, epoxy is fairly intolerant of high clamping pressures. Putting it outside, even in filtered sun, caused a shift in the MC from top to bottom and stressed the joint.

[Mel Fulks]

It’s a Pox on your Epoxy ! You need a good Gypsy to fix it ! I’m bringing back POX ‘cuz it’s scientific and contains no vile language.

[Mark Gibney]

I'm going with John TenEyck and John Lanciani - rip and reglue.
I'm wary now of using epoxy again - might Titebond III work on this tropical wood?

To John Kananis - it was clamped up very tight, and the mating edges were perhaps too smooth for epoxy (thanks Larry, sandpapering the edge might help). I bought the glue in a place that does a roaring trade so I'm confident the batch was fairly recent. And I made sure to mix it thoroughly.

Mel, I looked on ebay and craigslist but there's no Pox for sale right now. Maybe more available closer to Halloween?

Thanks for the good advice everyone. Mark

[Mel Fulks]

I had same trouble once. Someone informed me that Acetone has OIL in it. If you want to use it , I would then clean the surfaces
with denatured alcohol.
Epoxy should not get a lot of pressure curing , using it with pressure is bad, it’s an adhesive, not a glue.

[Michael Burnside]

Never had a problem with Epoxy. On porous wood I do nothing to the edge, otherwise a little 120gr scuff is enough. I've even glued up thermally modified wood without issue. And excessive pressure on the clamps = bad. Epoxy doesn't need a lot of pressure. One thing to realize is that epoxy takes 3-5 days to fully cure depending on hardener, but IMHO, clearly the wood shrunk. I personally would never let something sit in the sun until at least a week after, but that's just me and how I've always done outdoor furniture. Good idea to let it sit in the sun beforehand and do final milling/gluing after since wood will do what wood will do in any kind of direct sun.

Before I ripped again, I'd try to repair using a mixture of light and dark sawdust. The top is beautiful and with enough grain patterning I think you can hide it...or at least give it a try.

[Mel Fulks]

Titebond 3 Will probably work , if you remove the oil in the pieces.

And here’s a tip , never use mayonnaise as glue. Yes , it will stick two pieces of bread together….but NOT wood.

[Thomas McCurnin]

Unless you can clamp it closed, re-rip and re-glue it

[Doug Garson]

Is it possible you didn't wait long enough after wiping with acetone for the acetone to flash off completely? I agree with Michael, it's a small gap, try filling it with sander dust before resorting to ripping and gluing.

[James Schmidt]

Many epoxies are damaged by exposure to UV. In fact, when using epoxy on boats, you always need to have some sort of protective coating over exposed epoxy or the UV will degrade it.

[Tom Bender]

So that's flat sawn with the heart side up. Moisture content is always changing in wood. The top got dried and the bottom may have picked up a little moisture from the plywood it was resting on. I say resting but,,,always changing,,, The heart side is where to expect shrinkage cracks, shrinkage relative to the pith side.

[Mike Cutler]

I'm going with John TenEyck and John Lanciani - rip and reglue.
I'm wary now of using epoxy again - might Titebond III work on this tropical wood?

To John Kananis - it was clamped up very tight, and the mating edges were perhaps too smooth for epoxy (thanks Larry, sandpapering the edge might help). I bought the glue in a place that does a roaring trade so I'm confident the batch was fairly recent. And I made sure to mix it thoroughly.

Mel, I looked on ebay and craigslist but there's no Pox for sale right now. Maybe more available closer to Halloween?

Thanks for the good advice everyone. Mark

Mark

I don't know what type of epoxy you used, but there are many different formulations for different purposes. I prefer the West Systems product line. It's what I know from repairing boats. I've also used the System Three products, but they're not as easy for me to buy as the West products.
From your writeup and response, it seems that the joint may have been over prepared, and the clamping pressure enough to starve the joint. With epoxy only apply enough pressure to bring the material pieces in contact with each other.
Don't be afraid to use epoxy, thousands of gallons of epoxy are poured every year in the marine boat industry, and it works. These are tropical woods exposed to harsh environments. However, for a piece that is destined to remain inside the house, Titebond III would work just fine.
To fix it, yeah, you have to redo the joint. You'll kick yourself in the behind for not redoing it completely. ;)

[Brian Holcombe]

I would use Tibebond 1 or 2 unless this table is planned for outdoors.

[Mark Gibney]

Yes indeed, and now I'm regretting now using Titebond for this tabletop. I've made tops with salvaged ipe with Titebond I and they held perfectly.

I had figured epoxy was more fool and fail proof!

[Michael Burnside]

Epoxy generally is easier, but like anything, there are application rules and guidelines that if you don't follow, results will be less predictable.

[STUART Robertson]

Forgive this query...
When you did a dry fit prior to gluing did all the mating surfaces fit well and did you oppose each jointed face,and did you clean the biscuit slots and faces?
A profiled glue joint should also be superior,significantly more surface area.
And as others have said, variable wood movement.
Yes epoxy is intolerant of uv,but it takes a while.
Sun and rain,heat and cool,fairly brutal on exterior joinery.

[Mark Gibney]

Hey Stuart, here's a quick update - the gap has closed by up by it's own accord in the two weeks since this happened.

To answer your question, yes the joint went together perfectly with the test fit, and again perfectly with the glue-up. Some on here have suggested the joint might have been clamped too tightly and that pushed most of the epoxy out, and I think I agree with them.

I might run some thin CA glue into the joint before finishing the top. I tested CA glue on epoxy and it seems to adhere pretty well.

[John Kananis]

Mark, interesting that it closed back up. Did you move it to a different spot or flip it over by chance? Or is it sitting in the same spot and orientation where it first opened up?


Hey Stuart, here's a quick update - the gap has closed by up by it's own accord in the two weeks since this happened.

To answer your question, yes the joint went together perfectly with the test fit, and again perfectly with the glue-up. Some on here have suggested the joint might have been clamped too tightly and that pushed most of the epoxy out, and I think I agree with them.

I might run some thin CA glue into the joint before finishing the top. I tested CA glue on epoxy and it seems to adhere pretty well.

[Mel Fulks]

and .. epoxy is an adhesive , not a glue, don’t use pressure , or you will have ‘a POX’ on your project.

[Mark Gibney]

John I took it back inside the shop as soon as I saw it had opened up and left it in a quiet corner.

[John Kananis]

Must have been the quiet. :-)


John I took it back inside the shop as soon as I saw it had opened up and left it in a quiet corner.