# Glue failure on douglas fir



## gko (Jul 8, 2009)

I'm making a quick manger for our church out of scrap lumber. Found a piece of douglas fir from an old bed about 40 years old, cut it for a lap joint. Glued two faces, edge not end grain, Titebond II and clamped for an hour. After unclamping the parts practically fell apart. Tried it again with another two pieces and again it fell apart. I thought maybe the glue was too old but at about 6 months thought it was strange. I then glued it with Titebond III on another joint with the same result, they practically fell apart. In all cases the glued area was still sticky after clamping for an hour. I had glued another part using newer douglas fir and it was rock solid. As an experiment I glued two pairs of maple with the two glues and it was also rock solid. Is it the sap in the old wood? The cut areas don't feel sticky or look like there is sap in the wood. Never had it happen like this before.


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## RussellAP (Feb 21, 2012)

The weather is getting colder, what was the temp when you did this? Also the sides you clamped up, were they run through anything that would straighten them up so they go together flush? Pictures would help. I've never had any issues after an hour with TBII.


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## NiteWalker (May 7, 2011)

I don't think it was the glue; I think something in the wood was preventing a good bond.


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## gko (Jul 8, 2009)

I live in Hawaii and we had a cold spell yesterday….. 78 degrees LOL. I don't think the cold weather was a factor. The half laps were flat and true and the when the joint fell apart the glue was evenly spread. I even put a bunch together and ran a rabbit plane through them to make sure they were flat and flush. I've never had anything like this happen either. I did glue them with Gorilla polyurethane glue and they seem to be solidly glued. Really weird puzzle. I've heard that oily woods or wood with a lot of sap can weaken a glue joint but fir isn't an oily wood and freshly cut it doesn't seem to have a lot of sap.


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## JAAune (Jan 22, 2012)

High moisture woods will also prevent proper adhesion when using pva glues. Polyurethane adhesives such as Gorilla glue actually work better with moist wood. The situation you describe in the original post could be explained by this.

So the question is, did the old fir contain an unusual amount of moisture from laying around outside, on unsealed concrete or some similar location?


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## gko (Jul 8, 2009)

No, the bed was taken apart several months ago and the wood was stored in the garage rafter. Some of the newer woods that I tried gluing were stored there several years. I tried measuring the moisture and it read about 7 percent so it's not wetter than my other woods. New wood from dealers tends to be around 10-15 percent around here. I think the trip over the ocean tends to make them higher in moisture. When problematic I try to let the wood to sit around a few weeks before cutting. I've had problems with wood shrinking and causing joint problems if I use them right out of the store. Once wood has shrunk from drying out they tend to be pretty stable in Hawaii. At the low end humidity is around 60 percent and about 80 on the high end. Wood is very stable here. I've never had any problems with glue before this.


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## JAAune (Jan 22, 2012)

The next guess is silicone contamination. Some evil housekeeper probably ran around the house misting Pledge on every wooden surface in the bed's old home for 20 years straight.

Now that silicone has gotten into the wood grain and will migrate out at night to infect all your other projects inside the shop.


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## gko (Jul 8, 2009)

Yikes! I guess I have to bring in the exorcist to rid of that evil housekeeper.

Thanks for the help. I think it's some kind of sap in the wood but can't imagine it being everywhere I tried to glue.


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## Pete_Jud (Feb 15, 2008)

If I glue doug fir with tightbond II I leave the clamps on overnight, or use a screw to hold the parts together. And only in my heated shop. Outside here in the wet PNW, might never cure.


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## MonteCristo (May 29, 2012)

Something is off. I have glued tons of Douglas with Titebond and had no trouble at all. It's not a wood like teak or whatever that requires polyurethane glue or some other specialized concotion.


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