Finishes - polyester vs polyurethane

HAL9000

I recently dropped a MIM Tele and was surprised at just how brittle the finish is. Like an eggshell it is actually quite strong in normal day to day use but when it does break it is fairly catastrophic. I was also surprised at how thick the finish is. From Fender's website I see that it is a polyester finish, and that models higher up in the range sport a polyurethane finish.

I assume, then, that polyurethane is considered to be more desirable. Just wondering how it differs from polyester in everyday use. Tougher? Tone? Ease of application? Etc, etc.

Jack_

"For sale, MIM Telecaster, I'm asking way too much for it because it's from the golden days when Fender used polyurethane and not this modern polyester crap they're using today."

GoldenEraGuitars

From my understanding polyester was the next step up from nitro but the drying time and application made it redundant quite quickly. I didn’t know they still used the stuff tbh. It’s nowhere near as tough as polyurethane from what I’ve read hence it’ll act like nitro in that sense. 

My disclaimer is I’ve never knowingly played a polyester finished guitar tbh.

thermionic

Most “poly” Fenders are polyester bodies with polyurethane necks. Why not use the same stuff on bodies and necks?

Corvus

The whole thing's complicated by different terms here and over the pond, the possibility of different labels for the same things, and guitarist use of the word 'poly'. 1k was the next thing after celly. In the early days it wasn't great, the lacquer yellowed. It doesn't take well to high build and it's no tougher than celly/nitro. Mostly it's used as a thin base colour under a two-pack/urethane clearcoat - as in zillions of cars, as well as guitars.
Catalysed polyurethane and polyester also gets used as colour and clear.

57Deluxe

Polyester is lighter and the modern way.

ICBM

As far as I know almost all far-east made guitars are polyester finished and have been since probably the 1960s. It's the typical hard, glassy finish which is tough against minor scrapes and dents but chips and cracks in an unsightly way if hit harder. It's often fairly thick, but doesn't inherently have to be. I'm pretty sure it's used like that as Corvus said, deliberately thick so it's self-levelling and doesn't need any more expensive finishing.

Polyurethane and acrylic are softer and have a slightly more 'waxy' feel, closer to nitro. In fact, several of the classic Fender Custom Colours (eg Lake Placid Blue) from the 1960s were acrylic and not nitro, despite popular belief that they were all nitro. They were also undercoated in polyester...