What is "Premium PE" Finish?

[kauffmds]

Hi guys,

I've found a crack, just in the finish, on the rosewood back of my beloved Masterworks Alvarez MD95. I think the crack is only in the finish, and not structural. It's in a place, under the center back brace.

I downloaded the PDF from the Alvarez site and they say that the masterworks guitars are finished with a "premium PE" high gloss finish. Does anyone know what that means? Is it polyurethane, or some type of shellac?

The crack is just short of 8" long and is very hard to see; I had to put the guitar into the sunlight at the right angle to photograph it. I took a macro photo of the crack too.

I know the problem is the lack of humidity, even through we have a whole house humidifier attached to our furnace, we still have problems maintaining anything over 35%; the method that I used to humidify the guitar in the case wasn't good enough, so I'm using the Oasis now. To my horror, I noticed that my husband placed the guitar case by a vent, where it sat for quite a while.

I'm anal retentive about the care of my guitars, so this is very upsetting to me. The crack has not affected the sound of the guitar at all; the intonation, sustain, and overall wonderful sound and volume are just as sweet as ever.

Thanks for your help!

[charles Tauber]

Originally Posted by kauffmds

I think the crack is only in the finish, and not structural.

Almost certainly a crack in the wood as well as finish.

I don't know what "Premium PE" means.

[fazool]

I was just about to write what Charles said - and he knows a lot more.


I presume Premium PE is polyester. I don't have any Alvarez info but here is Taylor's description of their version of polyester.

Here is the bigger problem, and why Charles said what he said:

Any clear-coat has no grain and no "orientation". Crack propagation in such materials will be very erratic and almost random appearing. There is nothing keeping the cracks in a straight line.

When the wood splits, it follows the grain boundaries exactly. So the wood will split in a straight line.

When you look at a crack that wanders or runs across the grain, you know it is surface only, because it crossed the grain.

If a crack follows the grain, it is doing so because its following the wood. You could get a random straight line finish crack that coincidentally followed the grain direction, but the longer the crack, the more likely it is actually the wood cracked underneath.

Also, The finish materials are "flexible" so they don't crack when the wood moves. You will see finish "checking" which is the finish getting brittle, often from age - that's why old guitars can have tons of finish checking.

Humidity problems will (generally) make the wood crack, not the finish.

So, I highly suspect that your wood split from humidity issues and its taken some finish with it.

Sorry if this sounds like bad news - just trying to give you what insight I can.

[kauffmds]

Thank you for the information. I'll take it to a guitar tech and see what they say. Since the crack is under the strip of wood that bridges both sides of the back, down the center, will this stabilize the crack?