3 accordions, no varnish inside, Nonc. I heard about this discussion too, and it makes some sense to me. It might give some difference. Maybe you should use this 2 components stuff which gives a real hard surface.

I wonder if not any of the more experienced builders like Savoy already tried it and rejected it.
Which probably makes a difference: One of mine accordions has the reeds screwed on leather, no wax. It gives a drier and some say milder tone. But the reeds are different, so no direct comparision. Advantage: reeds cannot fall off in the trunk .

Gus

While learning to build accordions I studied the specs. of the most expensive and professional piano accordions and found that most of the best ones had the inside completely varnished, reed blocks and all. So that is what I did to my custom build ones if the customer wanted it. BTW, just a point of fact, I had been building furniture and woodcarving for many years before building accordions.

About the best comparison I can give anyone is to see the difference when you close the door of a car with all cloth interior and one with all leather. Now to a degree the one with all leather or naugahide sounds louder, especially older cars. Understandably this may not be the best comparison but you can notice the difference. Those accordions with varnished insides seem brighter and a little louder but then it may depend on the tuning. For instance, musette tuned accordions seem to sound louder.

I hope this helps guys.