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Yellowing Rosette

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Love O Fair
Posted 2019-04-16 10:38 PM (#547734)
Subject: Yellowing Rosette



Joined:
February 2016
Posts: 1139

Location: What week?
I have a few 70's-80's Ovations, but only one of them ('81 custom balladeer -1) has ever developed a significant rosette yellowing over time. If the yellow is on the surface, then it's beyond me for a way to lighten it aside from maybe an abrasive scrub which I won't do, and any typical cleaners have never made any change at all. And if it's on the inside then it's probably out of practical reach anyway. Fact is, I actually like the yellowing since it seems to represent age and character, but I am still curious as to what causes it and why it hasn't happened so much on others that are even older and have been kept in the same environment. Possibly a change in manufacturing materials used during that time? I dunno. Any answers for this?
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DetlefMichel
Posted 2019-04-17 4:52 AM (#547737 - in reply to #547734)
Subject: Re: Yellowing Rosette



Joined:
May 2011
Posts: 588

Location: Muenster/Germany
All plastic materials will with the time get structurally detroyed by age and especially by natural UV rays. Often you will notice a yellowing. Maybe your guitar was more often played outside than others. And an additional reason for yellowing on 70´s and 80´s guitars is - smoking. I remember well, playing the blues without smoke was unthinkable all these years, many of us had burned trussrod covers from the cigarettes that were fixed behind the low E string and then forgotten within the long slow blues soloing;-)
I don´t think that different materials are the cause.
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Love O Fair
Posted 2019-04-17 9:30 AM (#547742 - in reply to #547734)
Subject: Re: Yellowing Rosette



Joined:
February 2016
Posts: 1139

Location: What week?
@Detlef - >>>played outside ... smoking<<<

In this case I'd have to give both of those a nope. This particular guitar might at most have one hour total of outdoor/sunlight exposure in its life and mostly lives in relative darkness. And while it has in fact had some presence in smoke, it has been no more than the others that still have a bright rosette. Possibly even less. The finish is a burst, so it's hard to tell if there has been color change on that over time, but the wood surfaces and chrome tuning buttons are still very glossy and clean as it all gets a good cleaning and polish at least a couple times per year. All of them have.. but still this one rosette has yellowed.
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DetlefMichel
Posted 2019-04-17 10:32 AM (#547746 - in reply to #547734)
Subject: Re: Yellowing Rosette



Joined:
May 2011
Posts: 588

Location: Muenster/Germany
Did you try to polish the rosette? Thus you can find out if this is structural or superficial. I did repairs on old Ovations and I found out the old rosettes were made of a material similar to acetate or celluloid. Both of them react with lots of chemicals like polishing agents or sweat. Besides that it should be quite easy to replace it if someone has a rosette left.
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DanSavage
Posted 2019-04-17 2:24 PM (#547756 - in reply to #547734)
Subject: RE: Yellowing Rosette



Joined:
June 2012
Posts: 1978

Location: Lake Forest, CA

It's either the styrene pearloid or the glue used to attach the pearloid to the clear rosette shell that's yellowing. You can't do anything about it as the pearloid is glued to the back side of the clear plastic rosette shell.

Here's a close-up of the rosette that came off a 1978 1617. As you can see it's the front side of the pearloid that's yellowed. The back side of the pearloid and the clear shell is fine.

Also notice that the area of the wood top under the rosette is lighter than the surrounding area. Also darkened due to exposure to light.

Plastics turn yellow because of exposure to UV light, visible light, extreme temperatures, humidity or exposure to solvents. Primarily, it's exposure to UV that causes plastic to discolor.

(See: What Makes Plastic Turn Yellow? Hint: Sunscreen Won’t Help)



Edited by DanSavage 2019-04-17 2:46 PM
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Love O Fair
Posted 2019-04-17 4:49 PM (#547757 - in reply to #547734)
Subject: Re: Yellowing Rosette



Joined:
February 2016
Posts: 1139

Location: What week?
It's looking like the photo of the yellowed pearloid tells the best story since, again, the rosette has been cleaned and polished many times in its life, and exposure to UV has been pretty much zip. But I still have some wonder about why this one, in comparison to the others which appear to have the same type of plastic and pearloid, and that have lived right next to it for decades, is so much more yellowed. The rosette appears to be sealed tightly all around, but could it possibly be a tiny, undetectable air leak over so much time that the others may not have, and has oxidized the pearloid and/or plastic/glue to a yellowing effect in the trapped and enclosed space between? I hadn't considered that (out comes the magnifying glass).



Edited by Love O Fair 2019-04-17 5:03 PM
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DanSavage
Posted 2019-04-18 8:46 AM (#547761 - in reply to #547757)
Subject: Re: Yellowing Rosette



Joined:
June 2012
Posts: 1978

Location: Lake Forest, CA
How dark is the wood of the guitar? Is it very light blond or honey colored?
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Love O Fair
Posted 2019-04-18 2:15 PM (#547767 - in reply to #547734)
Subject: Re: Yellowing Rosette



Joined:
February 2016
Posts: 1139

Location: What week?
It's a burst, and I can only assume that the inner wood toward the center hole 'might' be the wood's natural color without any applied stain, and that is a dark honey color, far from light blonde. But I don't know about the process they used for coloring burst guitars.. if perhaps the factory shot any given tint of stain onto the entire top first and then applied the black outer edge over it, or just left the inner color natural. And it's not like the rosette is ugly dark, its not. It's just darker than it was new and also darker than others of approximately the same age. I will try to shoot some photo comparisons later today of two rosettes I have here that show the difference.
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Love O Fair
Posted 2019-04-19 8:23 PM (#547783 - in reply to #547734)
Subject: RE: Yellowing Rosette



Joined:
February 2016
Posts: 1139

Location: What week?
These two pics were taken in exact same location and lighting. They didn't turn out to show as much darkening contrast between the two as exists viewing them in person, but you can see some. Both of these guitars (1981 L & 1988 R) have lived next to each other for 30 years. I also have an early-70's 1127 that has been exposed to every angle of hell, though still has a lighter rosette than the 1981 (1,000 miles away, can't photo), and a 2008 that's too new for the comparison. Certainly no crisis, but I'm still curious as to why only this one has darkened.



Edited by Love O Fair 2019-04-19 8:27 PM




(Rosette Compare.jpg)



Attachments
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Attachments Rosette Compare.jpg (99KB - 0 downloads)
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DanSavage
Posted 2019-04-23 10:27 AM (#547808 - in reply to #547734)
Subject: Re: Yellowing Rosette



Joined:
June 2012
Posts: 1978

Location: Lake Forest, CA
Probably the glue used to assemble the rosettes changed during the period of the late 70s to the early 80s.
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Love O Fair
Posted 2019-04-23 5:54 PM (#547817 - in reply to #547734)
Subject: Re: Yellowing Rosette



Joined:
February 2016
Posts: 1139

Location: What week?
@Dan - >>>Probably the glue used to assemble the rosettes changed<<<

That's my ultimate guess, too. Or maybe a different plastic compound from the vendor.
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