Eastman stops using Nitro switches to Truetone

[donovantyler]

I'm late to the party on this one. As a builder, I have switched over to post-catalyzed conversion varnish on my instruments. One of the biggest advantages is the very quick cure time. Nitro has to sit for weeks before it's cured enough to final sand and buff, that's a big slow up in the production schedule for an operation that produces a lot of instruments. It also means you get to that same hardness that puts a crisp edge on the tone WAY faster. Nitro shrinks back and becomes thinner and harder over time. The biggest improvement is in the first few years, at ten years it can sound really good, in 30 years it can be fantastic (depending on the build). Cured finish is buffable in 1-2 days, and as cured as it will ever get in 30 days.

The fact that someone as meticulous as Dana Bourgeoise has made this change tells you something. Nitro is currently 3-4x as expensive as the synthetics (at least in the quantities I buy) but I doubt that's behind the change. When a Bourgoise goes for $5-6k new, they're not going to sweating $10 in finishing materials. His reputation is most important.

RoyBoy,
thank you for wading in here with your knowledge and experience sir.
I no very little about Lutherie or chemistry but maybe you could clear some things up in my mind..and of course it's the end-result that really matters..
Mark Herring said that the new finish is a "water-based laquer.  Very close to nitro." ... that it is thinner than nitro and will "age" like nitro with respect to color and he also said that he heard that it gets thinner over time (like nitro).
Yet Eastman calls it a dual part Urethane.
Is a water-based laquer a "urethane"? I would be surprised if it's water-based, I've not heard of any established builder of repute using water-based lacquer. Generally, it doesn't have the durability required. I would consider water-based lacquer to be about as far from nitrocellulose as you can get. I may be wrong about this, but I haven't heard Dana say anything about the actual content of his new finish, other than it cures really fast.
My concept of a urethane finished guitar brings to mind cheaper guitars with not-so-resonant sound. The newer catalyzed urethanes are easily as hard as cured nitro of many years. The key to resonance is the thinness of the finish film which all quality builders strive for and most productions are getting better at. The old days thick, soft polyester resin finishes are behind us (thankfully)

Mark also said that this is the same finish that Dana uses on his guitars.
Doesn't Bourgeoisie have three different finishes? Gloss, something else and an "antique"
Which one is Eastman using? (rhetorical question) Gloss and satin art the same finish chemically, satin just has a flattening paste of microfine particles suspended in it the break up light transmission through the film. I haven't really studied Bourgoise's finish options. He may be offering a "varnish" finish on certain models. Varnish is a slippery slope though because these days that label can refer to many different compounds. Older fashioned varnishes were softer, more fragile, and have a different tactile feel and tone that some prefer.

I'm guessing the bulk of Dana's guitars get whatever catalyzed finish he's using now. I read a quote from him that he's very satisfied with the final formulation he's settled on. I'm sure it will help him to achieve the scaled up production he's working on.

Interestingly, I just bought a new Martin Custom shop D-18 and it smells like play dough, whereas the Eastman had that sweet maple syrup scent that definitely says "nitro". The manual on my Martin only specs "high quality finish" but also warns about contact with alcohol, bug spray, etc. which says nitro to me (catalyzed finishes are immune to solvents). I queried the finish on the UMGF and someone there assured me that Martin uses nitro on their standard series and up.
Thanks! 

Thanks very much!