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Not strictly repair/restoration - I'm reworking a 70s Japanese-made dreadnaught into a tenor guitar based on the Lyon & Healey pear-shaped model from the 20s.

Back and sides are nice mahogany laminate, with three thin plies, so I've left the finish on while making the box because I have little room to sand out dings. Now I have to remove the finish.

Attacking it with a scraper I find it has two layers. A tinted top layer (hard as nails, resists solvents, so I guess it's poly) and a softer underlayer which is pale grey when scraped (vinyl sealer?).

Is my scraper the best tool, or might I try something else to speed up the work? Machine sanding is no quicker than the scraper and lots messier. I estimate about 3 hours total scraping - this stuff is unbelievably tough.

I have NEVER used this suggestion on wood but have you tried Aircraft Paint Remover in a aerosol? Spray it on with the guitar in a tight fitting cardboard box and close the tops to seal in the fumes and aid paint breakdown. You get this stuff cheap at Auto Zone or any parts store.
Ive used it to removed baked on finishes on metal gun parts.

Those chemicals aren't available here.

But I think I've cracked it - used the blade of my scraper plane (by hand) to take the tough outside layer off, then mechanical sanding followed by cabinet scraper/hand sanding. 40 mins to do the back, sides are for later.

Years ago I tried to refinish a beater parlor guitar for experience before I refinished a good guitar. It was so much work I gave up and will never try that again. Ive never seen a finish as tough to remove as a guitar finish. BTW have you tried brake cleaner?

Sanding will likely lead to burning through the veneer so I would avoid that route. A heatgun and a putty knife can do the job but if you burn the veneer it will not come out. I use a water based stripper called multi-strip. Works well on most finishes, may take 3-4 applications to get to bare wood.

_________________
Brian

You never know what you are capable of until you actually try.

https://www.howardguitarsdelaware.com/

Haven't burnt through so far, or come close, but the surface veneer is comparatively thick (over .5 mm).

What's working best, with about 10% of the work to go is as follows:

1. Scuff sanding by hand with 60 grit to break through the surface - this is the toughest part, and a scraper bounces off it! The finish is thick enough that these sanding scratches don't reach the wood.

2. Scraping with a cabinet scraper at 45 degrees to the grain direction - why this should work best is a mystery to me, but scraping along the grain direction achieves very little.

3. Hand sanding for the odd remaining spot of finish and to smooth for finishing.

It would, as I knew before I started, have been as easy or easier to build with new wood. But a friend gave me the guitar with a request to turn it into something which played, so I'm doing this to please him and also to make a better story about this instrument's origins.