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Blue tint in KTM-9
http://w-ww.luthiersforum.com/forum/viewtopic.php?f=10102&t=2267		 Page 1 of 1
Author:  Pwoolson [ Wed Jun 22, 2005 8:12 am ]
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I've been doing quite a bit of experiments with KTM-9 over the last few months to get the method down to a science. Things like burning through on purpose to see how it reacts. All went quite well.
So I shot my first neck with it and noticed the tell-tale blue tint that waterborns are famous for. It was only visible on the ebony binding and only out in the sunlight. But I thought this stuff wasn't supposed to do this. Anyone else had this happen? I'm pretty sure I can add amber tint and make that go away but what kind, and how much? Any tips? thanks Paul
Author:  John Kinnaird [ Wed Jun 22, 2005 9:57 am ]
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YUP
Same story here. In the sun you can really tell the difference. The blue is a kind of suspended particle that clouds and refracts and decreases the light penetration.
I have not tried the amber tint yet, but I am afraid that it would cause a muddying of the finish and decrease the clarity while it eliminated the blues

Here is a guitar that I refinished for a customer. I changed from KTM-9 to nitro. KTM-9 first

Nitro

The both polish out great! The coloration sure is different and the lighting was similar if not identical.

John
Author:  Steve Kinnaird [ Wed Jun 22, 2005 2:03 pm ]
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Man it hurts that you had to finish that thing twice! Once is torture enough, but two times--ouch.

Really pretty, though. I like the nitro better. Steve Kinnaird38525.9616203704
Author:  Jeff Doty [ Wed Jun 22, 2005 2:22 pm ]
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John,

Thanks for the pictures. Makes me want to work harder at getting my nitro routine down.   What is your spraying schedule?

Jeff
Author:  Michael McBroom [ Wed Jun 22, 2005 4:53 pm ]
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John, I don't wish to rain on your parade, but I'm a photographer and I've done catalogue work before.

First thing I noticed is that the exposure for the two guitars is entirely different. The tree bark in the background of the first photo has much more depth and detail than the second. I would suggest that you please recompose your photos and reshoot them such that the background appears identical between the two comparisons. Then, I myself, at least, will be more inclined to believe the rather striking assertions you have made.

Best,

Michael
Michael McBroom38526.0797222222
Author:  John Kinnaird [ Wed Jun 22, 2005 9:22 pm ]
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Good point Michael. When I said the lighting was similar, I meant they were both outdoors, no flash, using natural light, but the fact is, on the bottom photo there was even more sunlight than on the top. I think that is why the bark of the tree washed out. The extra light is when the blues show up so if anything the bottom photo would have even a greater tendency to show the blues.

JohnJohn Kinnaird38526.2736689815
Author:  John Kinnaird [ Wed Jun 22, 2005 9:24 pm ]
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Jeff
   My schedule used to be: fill, spray about 5 coats, grind that flat, spray about 4 more coats, wait two weeks, sand and then buff.
   Now my schedule is fill, coat with shellac, ship to Addam Stark
Author:  John Kinnaird [ Wed Jun 22, 2005 9:29 pm ]
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Here is what the back looked like indoors. I was really stoked at this point and had decided to go KTM-9 forever. The stuff is really easy to build layers, sand and polish.
Author:  Jerry Hossom [ Wed Jun 22, 2005 11:21 pm ]
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I think what you're seeing there in the KTM-9 is fluorescence, probably from the UV in sunlight, not a blue tint (same problem, different cause). Many plastics fluoresce under UV, and getting rid of it may not be as simple as tinting alone. Adding a UV blocker would help, but given that the nitro photo is even more exposed than the KTM-9 pic, I'd say that's pretty clear evidence.

Beautiful guitar.
Author:  Colby Horton [ Wed Jun 22, 2005 11:55 pm ]
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I had the same problem using Target USL. Indoors it looked pretty good, but when I took it outside under the sunlight I could see a blue tint. I tried using an amber tint on the next guitar and was still not really satisfied. Outside it just doesn't look as clear as nitro.
Author:  Dennis Leahy [ Thu Jun 23, 2005 2:25 am ]
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Hi Paul and John,

Thanks for sharing your blues experience. I'm sure you can see the blue in person, in the sunlight, but like Michael McBroom said, I don't think the photos tell the story the way your eyes are seeing it. Amazing things those little orbs in our eye sockets. Together with our brains, we are able to see so much more than film or digital CCD/CMOS sensor's can. This is especially true in different lighting conditions, where our eyes and brain so easily adapt to the light and give us good color data, but the cameras will get fooled.

Anyway, (as someone who has hopefully abandoned nitrocellulose and all its nasty trappings), this makes me wonder how important the blue cast really is, because the instruments will undoubedly see very little sunlight in their working lives. It does present a new challenge to photographing an instrument, however. The "old" adage of shooting outdoors on an overcast day may not be enough. Once I have an instrument in my hands that was shot with KTM-9, I am going to investigate using a warming filter (81B, or 812, or 81C) to reduce the blue cast in the photo.

For professional luthiers that are selling a dozen or more instruments a year, I think a relatively inexpensive mini photo studio (good digital camera, a couple of strobes in softboxes on light stands, and a backdrop - say, $2500), is a smart idea. But for "amateur" luthiers, the sun and an overcast day has always been a way to get around the need for studio lighting. If the warming filter makes the outdoor photo look more like what your eyes see indoors (under artificial light), they may be a very cheap way around the photographic problem. And again, I hope the real problem that KTM-9 has a blue cast in sunlight is no more overwhelming that the reality that nitrocellulose will yellow with time. We all got used to seeing amber lacquer, and equate it with old. I wonder how KTM-9 will look after 20 years?

DennisDennisLeahy38526.4766203704
Author:  Scott Thompson [ Thu Jun 23, 2005 9:18 am ]
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Matt over at the Grafted Coatings forum left a response to Paul on this subject. He states that it isn't the KTM9 but the underlying wood that caused the blue tint.

"What you are referring to as blue blush is not the KTM-9 itself, but the reflection of the substrate through the KTM-9 in the sunlight. Ebony being as oily as can be, would cause the blue-ish cast when clearcoated and held at an angle in the light.

KTM-9 is a water-white clear-coat that does not contain any ingredients that resemble a blue-ish cast."

http://ktmfinishes.proboards7.com/index.cgi?action=display&b oard=ktm9&thread=1119481125&page=1 Scott Thompson38526.7644328704
Author:  Jerry Hossom [ Thu Jun 23, 2005 2:10 pm ]
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Easy to prove. Paint it on something/anything besides wood and take it outside.
Author:  matt81 [ Fri Jun 24, 2005 2:10 am ]
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For us over at Grafted Coatings, this is the first we have heard of anything in regards to "blue tint" in the KTM-9.

We do trials using metal coupons that are meant to display variations of color. I took Jerrys advice, and brought the KTM-9 drawdown outside in natural sunlight and did not see any blue-ish tint in the clearcoat.

mattmatt8138527.466087963
Author:  Pwoolson [ Fri Jun 24, 2005 8:56 am ]
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Matt, with all due respect, I don't buy it for a second. I've brought other guitars out in the sun to see if your thoery is accurate and I only see it on the waterborne guitar. Never under shellac, never under nitro. It's definately some sort of reflective quality in the finish.
Author:  Dennis Leahy [ Fri Jun 24, 2005 2:54 pm ]
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Does anyone have both KTM-9 and nitro, as well as some "oily" ebony, that could do an A-B test? If a single piece of wood is cut, and each piece sprayed with about an equal build-up, I would think that would be a good test.

Dennis
Author:  Michael Dale Payne [ Wed Jun 29, 2005 4:25 am ]
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Paul I am with you here. I believe the solids in waterborne reflect a bluish tent. I do believe that KTM-9 is less apparent than Target, but that is just my opinion. In every lighting situation except sunlight KTM-9 is very close to undistinguishable, but in sun light you can tell. It has to have something to do with UV rays, because I don't see it indoors at all.
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