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This reminded me of Theodoric of York, Medieval Barber:

https://www.youtube.com/watch?v=edIi6hYpUoQ

Well darn look at that, same thing just happened to me. I hate to see this happen. Fortunately this was a local client. This was glued on with 192 and has similar results to Steves in the OP except it took a bit of fiber from the top with it. It has just about almost completely popped off. A couple taps with a chisel at the glue joint and the bridge was off. The footprint on the top is almost 100% glue free. Hardly required any cleaning up.

I used Woodies method using 315g hide clamped for 24 hours so we'll see how it goes.

It’s been over a year and the one I glued back on with 315 is still on there. Inspected it the other day and it still looks good.


Steve

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Steve Smith
"Music is what feelings sound like"

Good to know!

I suspect that when i had a few troubles it was because I was mixing the glue a bit too thin. I use less water these days if I bother with hide glue…

Hey Ed, are you gluing to torrefied spruce and, if so, what glue are you using?


Steve

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Steve Smith
"Music is what feelings sound like"

I use Titebond original now, the few problems I had were with HHG that I suspect I may have mixed too thin.…and yes, I was glueing to torrefied spruce. Have had no subsequent problems with TB.

Thanks Ed. I glue braces on torrefied spruce with Titebond and it works just fine so that makes sense.


Steve

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Steve Smith
"Music is what feelings sound like"

Martin's problems keeping bridges on torrified tops was exclusively with the highly-torrified spruce tops used on some special models of guitars. For the lower levels of torrification used on selected tops outside of the D-35 anniversary model, their usual adhesive - AR - worked as well as it ever does.

Last time I checked, Martin was still replacing those highly torrified tops under warranty, but did not report any unusual issues with low or mid-level torrified tops.

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For the times they are a changin'

- Bob Dylan

How do you tell 'highly torrified?' As you can see in the foot print of this guitar it is pretty dark and it has those dark streaks in it which I presumed were from the cooking process too. So perhaps this one is highly torrified IDK. The Torrified Sitka I got from Alaska Specialty is not as dark as this which is old growth (might have something to do with the color too) Red Spruce from Stewmac.

So have torrified tops lost some momentum in the industry? I don’t see them marketed as aggressively these days.

Never got on that bandwagon. I do bake newly purchased tops at 200 degrees for an hour or so and say it’s a good thing. I have almost convinced myself. .

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It's not what you don't know that hurts you, it's what you do know that's wrong.

That’s the advantage of getting it done yourself, you get to choose the amount of torrefaction. Sadly I forget the recipe I used last time, thinking I’d remember. About as bright as putting something in a safe place, lol. Fortunately more people seem to be willing to share specs about this so finding a good recipe should be doable. I know for myself I want it very lightly cooked, rare to medium rare at most. I do recall that there were permanent dimension changes in all three dimensions, and an overall stiffness to weight ratio improvement of a pretty consistent 15%.

It seems like they’re not such a hot topic anymore, but I still get a fair amount of orders for them. I often turn clients away from it as it has to be the right choice. It works as advertised, very much giving a smooth, mellowed, broken in feel right from the get go, but it comes at the expense of tonal complexity and headroom. So I consider it a niche wood like using a hardwood top. But when it’s the right choice, it really is!

Martin does not automatically replace high torrified tops. Only if they are damaged beyond repair. Same as all tops . This is per Martin

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

If it ain’t broke…

I guess I was lucky. I've only done one torrified top guitar, and that was 3 or 4 years ago. I used titebond and clamped it overnight. Probably dooming myself here (I'm an ex-IT guy. Never ever say "system hasn't been down in a long time...") , but it's still holding just fine. If it pops off tomorrow, I'll delete this post and maybe it will be OK again.

Dave

If I indicated automatic replacement on demand, I apologize for the lack of clarity. Replacement of those level 3 tops after failure of the bridge/top joint absent other evidence of misuse was what was indicated to us in discussion with Martin.

Also, I suspect we may have dated info or were talking to the wrong people, Mr. Hall. IIRC, the discussion I based my post on was with one of the directors and occurred nearly a month ago. Your info was likely more recent and with someone at the VP/SVP policy setting level.

I can certainly understand Martin's concern with their position being misinterpreted as a blanket recall of those highly torrified tops.

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For the times they are a changin'

- Bob Dylan

This thread has had a good run with a variety of shop practices. Thanks for a robust discussion of the topic.

The source and excerpt listed below states that planed wood surfaces provide better adhesion than a sanded surface. It also speaks to equal moisture content of the wooden surfaces being glued.

HomeAircraft Wood and Structural Repair
[cite]Preparation of Wood for Gluing - Repair of Wood Aircraft Structures
Satisfactory glue joints in aircraft should develop the full strength of the wood under all conditions of stress. To produce this result, the conditions involved in the gluing operation must be carefully controlled to obtain a continuous, thin, uniform film of solid glue in the joint with adequate adhesion to both surfaces of the wood. These conditions required:
~Proper and equal moisture content of wood to be joined (8 to 12 percent).
~Properly prepared wood surfaces that are machined or planed, and not sanded or sawed.
~Selection of the proper adhesive for the intended task, which is properly prepared and of good quality.
~The application of good gluing techniques, including fitment, recommended assembly times, and adequate equal pressure applied to the joint.
`Performing the gluing operation under the recommended temperature conditions.[/cite]

Source: https://www.aircraftsystemstech.com/201 ... -wood.html

In my limited experience (new builder) with using torrefied braces (and tops) I have noted that after applying [Luthier's Mercantile] White Instrument Makers Glue to a torrefied surface, it does not "wet" the torrefied surface very well. Allowing a minute or two after application of glue, then brushing in the glue with a scraper/ finger/ brush, result in a completely wetted and uniform layer of glue on the torrefied and freshly sanded (220 grit) surface. I have not used HHG for bridge gluing.

On a related note, I use Fish Glue on repairs where PVA glue might have been used in a previous repair; adhesion tests in my shop showed that Fish Glue bonded tightly to PVA glue.

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Measure Twice,

Karl Borum

That's interesting about the fish glue. I have tested PVA to PVA glue and was surprised at how strong that was too, not that I would ever do it but still. None the less it's easy enough to remove glue from the bridge and foot print so that's not even an issue.

Alan Carruth has brought up the airplane study in the past and since reading that I always give a fresh scrape to all gluing surfaces.