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Periodically this pops up on the various woodworking fora. There is currently a discussion on another forum about this topic. Most in that discussion agree that a solvent wipe is not needed and may actually weaken a well prepared joint. "Conventional wisdom" is a well prepared fresh joint should not need any solvent. A sticking point seems to be that the tightbond instructions recommend wiping joints before gluing. Can you shed some light on the issue?

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Bryan Bear PMoMC

Take care of your feet, and your feet will take care of you.

All I can offer is that in 35 years of woodworking, I've never wiped down a joint with solvent. To my knowledge, I've had one joint failure (and that was humidity related).

That includes at least 20 Cocobolo fingerboards, headplates, and bridges.

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http://www.chassonguitars.com

I too, am in the "it is not needed" camp, but would like to know if Franklin has any data that has caused them to include it in the instructions.

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Bryan Bear PMoMC

Take care of your feet, and your feet will take care of you.

Disclaimer, I haven't done this experiment.



Do an experiment for your self, and I suspect you'll find the answer. You'll need 6 pieces of Cocobolo, or other oily wood to glue together.

1st pair, just glue it together. If you have to prepare the joint for gluing let it sit a few days to oxidize before gluing.
2nd pair. Wipe it with acetone. If you have to prepare the joint let it sit a few days to oxidize before gluing, but wipe it before gluing.
3rd pair. Prepare a fresh joint, and glue it. No wiping, but glue the freshly scraped or planed joint that isn't oxidized.

I suspect the "just glue it together" joint will fail pretty easy, but the wiped joint will be better. I also suspect the freshly scraped/machined joint will be the strongest.

Again, Disclaimer. I haven't done this experiment. I'm also allergic to Cocobolo, but I routinely use other oily woods with freshly prepped joints and no wiping. I suspect that Franklin has found that wiping an oxidized joint may help with adhesion. I also suspect that oily woods will oxidize quicker, or worse.

I don't research/read about alot of stuff. Alot of my thoughts on stuff may be mis conceptions. I don't wipe joints with acetone, or anything else. I use hot hide glue, but don't think titebond would be any different in that respect.

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I didn't mean to say it, but I meant what I said.
http://www.brackettinstruments.com/

You left out the case of wiping a fresh joint with solvent.

I'm absolutely certain that the clean fresh joint will trump all others, and pretty sure the solvent wiped old joint will be worst though I'd love to be surprised on that one. Whether an old uncontaminated joint is worse than a fresh but contaminated joint is an interesting question, though.

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Bob Garrish
Former Canonized Purveyor of Fine CNC Luthier Services

Only to strange people

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http://www.chassonguitars.com

Wow, sorry for my late response... I clearly haven't been around much lately. For future reference, if you have an urgent adhesives question 1-800-347-4583 will ring directly to the Franklin International (Titebond) Tech Service Line. I have several colleagues who are very capable of answering questions, and if the conversation turns technical enough about guitars you'll probably end up talking to me sooner rather than later.

Surface preparation is important for oily woods (ebony, rosewood, cocobolo, etc.) and can be accomplished both mechanically and chemically. Some wood species accumulate surface oils over time, and can impair bond formation with water based adhesives. Essentially, the oils repel water and prevent interaction with cellulose at the wood interface. Freshly machined pieces (generally within a few hours) can be glued up successfully without further treatment. Wiping the surface with acetone will never harm bond strength, and has only proved advantageous in our tests regardless of wood species. As a general rule, oily woods require additional clamping time of up to 24 hours only because the drying process can be slowed.

The question of solvents that can be used for this purpose comes up from time to time... and there is a reason we recommend acetone over others: it flashes off quickly and doesn't leave much behind. At the same time it is relatively aggressive towards oils. If anyone wishes to see this I can wipe a piece of cocobolo and post a picture of the orange oils that result.

When in doubt: wipe it with acetone and a clean rag.

Thanks Hugh! I'd love to know more about the tests you have performed and the results. Too many questions to just ask, are these data and methods published anywhere? Also, is it okay if I paste your response on the other forum?

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Bryan Bear PMoMC

Take care of your feet, and your feet will take care of you.

Both formal and non-formal tests are used. Non-formal methods can be as simple as assembling rub joints and breaking them with a chisel and hammer. Formal methods are for the most part derived from ASTM specifications, most commonly the D905 shear strength test when working with wood glues. ASTM methods are copyrighted, so I can't share any of them directly. That doesn't prevent me from explaining them in depth if necessary. In most cases lack of surface preparation leading to failure will create an adhesive failure situation, where it literally fails to bond and minimal wood failure is observed. If I can track down any test data on this I will share it.

Feel free to re-post, most of the time it happens without my knowledge anyways. A PM'd link to the thread would also be appreciated.

There are a lot of myths and commonly held misconceptions in the world of adhesives, and few resources for answers. I enjoy public speaking/Q&A sessions, and could probably pull them off with some regional groups of luthiers... Which could be a *lot* of fun. In the interest of disseminating information I wonder if publishing monthly (at least) in depth articles over topics in adhesives as they relate to woodworking might be a good solution? Would anyone be interested in something along those lines?

Hugh, if you're game, I'd love to hear the end of the "HHG sounds better" story. I don't care which way it goes or if there's no difference. But I'd like an answer! I can help with DOE/testing/analysis if you want, which might help insulate you from a "vested interest" accusation.

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Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

http://www.goreguitars.com.au

Yes - Do it on some sort of Blog site so that there's a searchable archive!

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http://www.birkonium.com CNC Products for Luthiers
http://banduramaker.blogspot.com