Replies

1. 
   thebardowl | Mar 27, 2022 12:26am | #1

   Unless you can get the surfaces to be approximated back to plain wood, Titebond I/II/III won’t bond well. Advantages of epoxy: it’s likely to be thin enough as mixed to penetrate well into the spaces, it can also fill voids/gaps, and it will bond even to old adhesives (generally, anyway). And you can get a long open time to get it together, with a reasonable hardener choice. Epoxy will be more than strong enough, if the joints are reasonably well made. Can also be tinted if necessary. Down side: It’s a one-and-done attempt, pretty much, and can be a little messy. It’s still what I would use, however, for its advantages.

   If you’re unsure about using epoxy on the chairs’ joints, I’d suggest doing a practice run or two on some similar joints you can make out of other (presumably scrap) lumber, just to get the process clear before you do one of the “have to get this one right” joints. (Securing and clamping curved chair parts can give one fits, or so I’ve been told….)

1. 
   woodstock16 | Mar 27, 2022 11:44am | #7

   Please see pic.

2. 
   rob_ss | Mar 27, 2022 02:33am | #2

   Chairs are challenging, predominantly because you do really need a quality joint and clamping is challenging.

   If you are able to disassemble the joints, loose ones need to be repaired - veneer glued to tenons is your friend.
   Thing is, if you are thinking of using epoxy, then the joint is not good enough and will likely fail. I'd make one exception - where almost all of the joint is good and tight, but you have a defect that is needing filling but too small to be worth a formal repair - epoxy will fill that really well.

   I enjoy the following two channels, both of which get deep into the weeds of antique restoration.

   https://www.youtube.com/c/ATRestoration
   https://www.youtube.com/user/johnsonrestoration/videos

1. 
   thebardowl | Mar 27, 2022 09:36am | #3

   Excellent points about the need for adequately tight (and appropriate) joints. I should have clarified that use of epoxy can’t replace good joinery.

   That said, I think it has a role in repairs in which the joint isn’t quite as good and tight as one would like, but getting the joint repaired to be so will be a long and difficult chore. I’ve made this condition arise in the midst of disassembling joints and clearing away old glue. I should probably recognize that I’ve not yet adequately mastered the use of veneer to rebuild/repair tenons, and if I were to do more repair work, I’d need to do so.

   BTW, I second the usefulness of the links you shared; I just learned a bit from visits there this AM.

   I guess the main point should be this: the best plan is always to repair the joint itself such that it is a good bit of joinery; then the gluing becomes at least less difficult, and much more likely to contribute to a strong and lasting repair. No glue can by itself solve the problem of bad joinery.

1. 
   woodstock16 | Mar 27, 2022 11:44am | #5

   Please see pic.

2. 
   woodstock16 | Mar 27, 2022 11:44am | #6

   Please see pic.

3. 
   woodstock16 | Mar 27, 2022 04:17pm | #10

   Great links to good information, I got a few ideas. Thanks

3. 
   woodstock16 | Mar 27, 2022 11:44am | #4

   Here is what I am trying to fix.

   
1. 
   john_c2 | Mar 27, 2022 03:38pm | #8

   For that, I would use liquid hide glue. It's a nice clean break, and should glue really well.

   Please avoid yellow glue or epoxy. Future conservators will thank you.

1. 
   woodstock16 | Mar 27, 2022 04:16pm | #9

   I am reattaching the veneer with hide glue but I was concerned about the strength of the joint.

4. 
   rob_ss | Mar 28, 2022 03:37am | #11

   FWW did an article on glue strength - Old Brown Glue have shared it - http://oldbrownglue.com/images/articles/HowStrongisYourGlue_FWW.pdf
   Realistically, any common wood glue is going to be stronger than the wood in that application. The problem is why it failed in the first place, and can it be prevented from happening again.

   This has happened most likely either because the dowel was oversized for the hole (or glue caused hydraulic damage) weakening the wood when it was made, or far more likely, the dowel worked loose, allowing leverage to act on the loose piece, shearing it off. The wood was also not well chosen for it's location suggesting a mass-produced item - the short-grain is a giveaway, and of course the grain is shortest where the dowel has the most leverage.
   Someone leaning back on this is going to exert a lot of force, especially if the joints between the leg and the rails are also loose....

   You have three choices -

   1. Glue the piece back on with hide glue or PVA, fill the dowel hole and re-drill then re-dowel. This will fail in time for the same reason, but it is an honest to the wood repair. Like as not it will fail next to the glue line as that will be the next weakest spot.

   2. Do the above, but instead of a dowel use a slip tenon. A small domino would be ideal - I don't have one so would use a router to create a suitable slot. This moves some of the leverage to a part that has better longer grain, and spreads the load somewhat. Slip tenons are not as prone to failure as dowels as they don't change shape as significantly with humidity changes

   3. Re-make the piece with a new bit of wood, this time aligning the grain correctly, including mortice and tenon joinery. This is the only way to make the piece last, but of course is the most work and a chair held together with dowels is going to fall apart somewhere else sooner rather than later anyway.

   Whatever you do, try to let your friend know gently about the grain direction issue - that way they will know to expect a failure and not blame you down the line. If you are as blunt as I have been then they will probably not stay friends!

1. 
   Jkatzowitz | Mar 28, 2022 08:09am | #13

   Rob, I think your analysis of what caused the break and your suggestions for repairing it are right on.

   Next time I have a structural issue to solve I'm calling you!

5. 
   john_c2 | Mar 28, 2022 08:05am | #12

   Shield-back chairs are pretty, but a lousy design. They are just very much prone to breaking. The originals were very light, and were the new "fad" for those wanting to get away from the visually heavier designs that came before them. The shield-backs were just asking an awful lot of the joinery. The things were just made to fall apart.

6. 
   revbob | Mar 31, 2022 01:06pm | #14

   Note: the dowel doesn't appear to have been glued, no doubt contributing to the joint weakness, which was depending on the very little wood in place to hold the strain. Put it back together with a dry dowel (low moisture) using your choice of glue and it should be good to go. Sometimes we overthink this stuff.