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Face Gluing Problem: Walnut & White Oak

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Forum topic by JZS posted 12-12-2013 07:46 PM 2225 views 0 times favorited 9 replies Add to Favorites Watch
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JZS

5 posts in 1094 days


12-12-2013 07:46 PM

Topic tags/keywords: face glue cupping question walnut oak

Was wondering if anyone could comment on a recent problem I had. I face-glued quarter-sawn walnut and quarter-sawn white oak, ca 21” L x 12” W, each panel ca 1/2” thick for glued-up thickness of ca 1”. I chose quarter-sawn for both the walnut and oak not only for the appearance, but also to try to get around any wood movement issues that might arise from the different wood species. I used Titebond III and many many clamps. I’ve face-laminated before with no problems, but have always used the same wood species. My problem is that the glued-up panel has slightly cupped ca 1/8” over 2 weeks (convex on walnut side; concave on oak side). This is the first time I’ve face-glued two different wood species together so wondering what I’m missing, what is the collective wisdom?


9 replies so far

View Dallas's profile

Dallas

3599 posts in 1955 days


#1 posted 12-12-2013 07:58 PM

Really need pictures here.

Are you saying you placed the boards face to face, and the cupping is at the glued faces?

If so, I would be tempted to say that you have wet wood, or the wood wasn’t set so the grain is alternating.

Seriously having difficulty seeing this problem in my head.

I am also sure someone else will be able to help a lot better than I can.

-- Improvise.... Adapt...... Overcome!

View Richforever's profile

Richforever

755 posts in 3188 days


#2 posted 12-12-2013 08:05 PM

Haven’t done this before, but the walnut might be a wood with more oil than the oak. Seems like I read articles about teak glue ups needing a different type of glue because of the oil content. Maybe try scraps with white rather than yellow glue, and some with hide glue.

Good luck!

-- Rich, Seattle, WA

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bondogaposis

4037 posts in 1819 days


#3 posted 12-12-2013 08:19 PM

A picture would really help here, but if I’ve conceived of your problem correctly I think the the wood picked up moisture from the glue and the walnut moved more than the oak. Let it sit for a week in dry environment and maybe it will look better. The only recourse is to mill the cup out, this will result in a thinner board.

-- Bondo Gaposis

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JZS

5 posts in 1094 days


#4 posted 12-12-2013 11:20 PM

Guys, thank you for your suggestions. Sorry I did not include a photo. I like the suggestion that moisture from the glue caused one board to move more than the other. Bondogaposis – why do you think the walnut had more movement relative to the oak? I’m looking at a table of shrinkage rates and the white oak has a slightly higher shrinkage rate than walnut, I would have guessed that oak shows more movement?? Tangential/Radial ratio is 1.8 for white oak and 1.4 for walnut. Jeez, I would have guessed there would not be much difference in movement based on those ratios, but I’ve never really thought about this in such detail before. Like you suggest, I’ve already milled out the cup, but I’m really stumped why the wood moved as it did, so I guess these T/R ratio differences are really significant with such a large surface area of wood contact in face-grain glue-ups?

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bondogaposis

4037 posts in 1819 days


#5 posted 12-12-2013 11:33 PM

I suspect that the walnut moved more because you said it was concave on the oak side therefore I reasoned that the walnut got wider than the oak did.

-- Bondo Gaposis

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JZS

5 posts in 1094 days


#6 posted 12-12-2013 11:41 PM

Ah, good logic, thanks!

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WDHLT15

1572 posts in 1944 days


#7 posted 12-13-2013 02:51 AM

Walnut dries fast. White oak dries slow….......at least twice as slow as walnut, so, if the boards were not in equilibrium and there was a bit of a moisture change, the rate of shrinkage or swelling of these two woods is different, even if the total shrinkage or swelling in a total sense is close. The rate of change is different, and that could set up stress.

-- Danny Located in Perry, GA. Forester. Wood-Mizer LT40HD35 Sawmill. Nyle L53 Dehumidification Kiln. hamsleyhardwood.com

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JZS

5 posts in 1094 days


#8 posted 12-13-2013 01:49 PM

Thank you, I did not know that white oak dries so slowly.

It sounds like my idea of face gluing 2 different wood types together to make an interesting looking panel is just not such a good idea, but that’s why I did the experiment. Just another question: I used quarter-sawn thinking it would give me the best shot at long-term stability, but was that thinking correct; should I have used plain-sawn or would that have made it worse? I’m giving up on this idea and changing my design, but was my original thinking ok for using QS?

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WDHLT15

1572 posts in 1944 days


#9 posted 12-13-2013 02:08 PM

QS is definitely best as it has the least shrinkage across the face of the board. When I saw walnut, I can air dry it to 15% in about 4 months here in GA. White oak takes 8 months. This is 4/4 stock.

In my DH kiln, walnut will dry in two weeks, white oak requires 5 weeks. If you do not go slow on white oak, it will honeycomb (internal failure of the wood).

-- Danny Located in Perry, GA. Forester. Wood-Mizer LT40HD35 Sawmill. Nyle L53 Dehumidification Kiln. hamsleyhardwood.com

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