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Author Topic: Finish Issues/Polyester and others  (Read 1323 times)
Danny
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« on: October 16, 2010, 01:06:26 PM »

   I was in a guitar shop in Albuquerque called Grandma's a few days ago and played a few guitars.
One was a great sounding smaller bodied Gibson with a cutaway. I can't remember the model, but it was about the size of a Nick Lucas.
    Anyway it had a really bad case of what most would call ''Orange peel'' finish. It looks like the pore filler was not applied at all or the finish just sank into the RW pores anyway. This was worst case of this I have seen. I saw a Larrivee LV-09e like this a few years ago, just not quite as bad.
    I also have seen a Taylor, SCGC and some others with sunken finish. Taylor and Larrivee both use "UV cured Polyester". Bob Taylor did some experimenting until he came up with this method. From the way it sounds in things I've read their was some sharing of experience with JCL and Bob Taylor. At any rate they both use an identical looking oven and fast cure method. Taylor just uses a thinner layer of polyester from what I see. My own 2000 model 615ce has a thin finish and very slight sinking of the finish on the darker areas of the big leaf maple. Most would never notice this, but I examine my guitars under very good lighting.

   The Gibson that looked so bad didn't need good lighting however and neither did some of the others I have seen. ( I would buy that gibby btw, if the price was right, nice tone and playability)

     So if you have seen this I'd be curious to know about it. It seems it's not limited to the type of finish used, but more of a pore filler issue. Maybe someone with some knowledge and experience in finishes could enlighten us
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Michael T
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« Reply #1 on: October 16, 2010, 01:21:27 PM »

I have a 8 year old DV09, & a 2 year old L05-12. Neither show any pore shrinkage.
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tadol
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« Reply #2 on: October 16, 2010, 04:33:33 PM »

Just a note - orange peel finish usually looks like the skin of an orange, where the pitting or shrinkage is not related to the woods natural pores in any way and look like pin points or small divots. Usually contaminants or application problems - silicone is a major problem, which is why you see all the warnings about using silicone products on finishes - once the silicone gets onto the material, it is very difficult to remove. What I've seen on numerous Larrivees is finish that has sunk into the pores of the wood either because of no filler, minimal filler, or minimal amount of finish. I've seen it on mahogany, koa, and rosewood Larrivees - but not on too many of them.

To keep the amount of finish to a minimum, that's a risk that you take. I prefer it to a guitar that has that "decopauge" look of thick resin poured over the whole thing, but appropriately applied grain filler that allows a minimal amount of topcoat to be applied and still get smooth, even coverage overall is still the ideal - 

I think the finishing is a very difficult and expensive part of the process of building a guitar - lots of smaller and custom builders send their instruments out to get it done, and I imagine its one of the biggest problems for small producers that can't afford ( or have the volume ) to keep a finish shop open full time -
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jimmyb
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« Reply #3 on: October 16, 2010, 06:14:41 PM »

Here's a good (bad?) example of orange peel. This is my former P-09 with a glossed headstock. I was not brave enough to take the finish down further to eliminate the orange peel.

Jimmy

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sgarnett
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« Reply #4 on: October 16, 2010, 06:36:54 PM »

I've always heard "orange peel" used to describe the texture that can develop during spraying (depending on technique, solvents, etc).

Sometime in the last 20 years, I read a Larrivee article on the effects of humidity that mentioned the pores. As wood expands in high humidity, the pores enlarge and the finish can sink. I have seen that happen once. As wood shrinks in low humidity, the pores contract and squeeze the finish out into very tiny raised bumps. I've never noticed this myself, but of course I haven't tried sticking a guitar in the attic to test it.
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tadol
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« Reply #5 on: October 16, 2010, 11:15:47 PM »

Humidity explains alot of it, actually - The workshops are kept at a very high humidity level ( I remember the misters running inside the building when we were touring ) so the wood is at its optimum humidity level - If they fill the pores, and apply the finish at that level of humidity, then as soon as someone lets the guitar dry out some, the wood will shrink and the filler ( and finish ) recede slightly, leaving the "open pore" look I've noticed - At that point, no amount of re-humidification will actually bring it back to smooth - at least thats the best guess I can make.
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Danny
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« Reply #6 on: October 17, 2010, 02:53:25 AM »

  This all makes good sense to me. Tad your posts are very thorough in explaining the process.
 I think the humidity aspect that was touched on is the issue here. If you look at my post you'll see that I'm in New Mexico right now and the Gibson that had this issue to the "max" is here. So there is a good chance it got dried out. And the others I've seen probably had the same happen to them. btw, I have seen this mostly on rosewood. I don't know if that's due to the wood itself or the color allowing it to be more visible.
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sgarnett
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« Reply #7 on: October 17, 2010, 04:38:30 PM »

as soon as someone lets the guitar dry out some, the wood will shrink and the filler ( and finish ) recede slightly, leaving the "open pore" look I've noticed
I think you've got that backwards. Drying shrinks the pores, squeezing out the finish. Or, I've got it backwards. Either way, humidity does affect the appearance of the pores.
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