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CSI: KTM-9 - Smoking gun found
http://www-.luthiersforum.com/forum/viewtopic.php?f=10102&t=4429		 Page 1 of 1
Author:  Pete Licis [ Mon Jan 09, 2006 3:05 am ]
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Hi folks!

First, I'd like to thank you all for the help provided in troubleshooting the finish problem I had.

Over the weekend, I discovered I had what appeared to be new lines of blistering/pitting on my finish. In order to photograph them, I threw some masking tape, cut up in thin strips, over the lines. See below:



Then, without moving the sheet the instrument was resting on, I carefully took a couple of shots of the sheet with different light angles to bring out the wrinkles and the lay of the sheet. Then I superimposed that on the shot of the instrument. I think the answer is self evident!





I have no clue what the heck could be on the sheet to cause this, and I'll probably never find out. But I guess that's OK - I just need to prevent it in the future.

If I could ask for a little more help,

1) What do you guys lay your instruments on while working on it after the finish is done?

2) How would you suggest I fix the finish? I thought I could sand back a little, treat with alcohol, and apply more coats. At this stage (1 month +), the finish still responds to alcohol. If I swab some on, the gloss becomes haze, so perhaps with a sanding to remove the defects, and application of alcohol, additional coats of KTM-9 will adhere. Any thoughts?

Thanks again for the generous help you've given me!
Author:  Mario [ Mon Jan 09, 2006 3:28 am ]
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Problem here is, if this was the cause, the lines in the back would be mirrored to the wrinkles, and not indentical, no?
Author:  Pwoolson [ Mon Jan 09, 2006 3:40 am ]
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Pete, I'm not being a smart-mouth when I say this. But what about ironing the sheet? Even if it's just a small area that the guitar will rest on. It seams as though the sheet didn't effect the finish on the "flat" areas. Might be worth a try.
Author:  Michael Dale Payne [ Mon Jan 09, 2006 3:42 am ]
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[QUOTE=Mario] Problem here is, if this was the cause, the lines in the back would be mirrored to the wrinkles, and not indentical, no?[/QUOTE]

I believe this is an overlay image. I think the image of the back was mirrored prior to overlaying on the image of the sheet. or vise versa.MichaelP38726.4885300926
Author:  Josh H [ Mon Jan 09, 2006 3:52 am ]
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Next time you might try hanging the guitar to dry and this would become a nonissue. I don't like to let the guitar rest on anything once it has the finish on it. After it has cured for a few weeks you should be fine to set it wherever you like.

Josh
Author:  Wayne Clark [ Mon Jan 09, 2006 3:56 am ]
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I'm with Josh on this one. As soon as I start the finish process I hang the guitar to dry. I have a piece of carpet that I lay it on for sanding, etc. but only after the finish hardens.
Author:  Pete Licis [ Mon Jan 09, 2006 3:59 am ]
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Mario ... good thought. The photo of the sheet is mirrored in Photoshop. Sorry I didn't tell you!
Author:  Wayne Clark [ Mon Jan 09, 2006 4:00 am ]
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Oh, and for what to do now I would probably sand back to wood and start over.

I have made some small touch-ups on KTM-9 but can see witness lines. It seems like a lot of work, but that is a pretty guitar. If you end up with a bunch of witness lines in the finish, you probably won't be happy with it.
Author:  Pete Licis [ Mon Jan 09, 2006 4:01 am ]
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Josh,

The guitar did hang during the 1 month KTM9 cure. The problem appeared after buffing, while working on things like attaching the neck, when I rested the guitar on the sheet.Pete Licis38726.5022569444
Author:  Mario [ Mon Jan 09, 2006 4:37 am ]
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What is the sheet, then? What could be on it? Was it washed with fabric softener at some point?
Author:  Josh H [ Mon Jan 09, 2006 4:42 am ]
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Pete

I didn't relize that, I guess I didn't read your posts close enough. Sorry. That is sure an interesting problem. I did 4 or 5 guitars with KTM and didn't run into that one (I have since switched to nitro). And my cure time was only 2 weeks.

As far as fixing it now, is this the kind of thing that you can sand out and rebuff?

Josh
Author:  Pete Licis [ Mon Jan 09, 2006 4:57 am ]
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Mario, those are just some old cotton sheets that my wife through in the washer/drier. I'll have to ask if she used any fabric softeners or "Bounce" in the drier.
Author:  Pete Licis [ Mon Jan 09, 2006 5:00 am ]
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Josh, I haven't experimented with sanding yet, but I know that buffing with Menzerna Extra Fine and then Glans Wachs subdues it somewhat. The thing I'm afraid of is that last week I did a finish thickness test with my method of application, and the final answer came out really thin. I'm afraid that any more sanding may sand through.

If I can avoid going through the epoxy, yet still have adhesion to the old KTM9, it becomes more convenient.
Author:  Josh H [ Mon Jan 09, 2006 5:13 am ]
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Pete

If you go through the epoxy you will be sunk. I went through on a top once and ended up removing the finish on the top and spraying again. You could refinish the back only. You might try some more buffing with a courser grit, but you do run the risk of buring through.

Is this guitar for you or someone else? If it was my personal instrument I might be tempted to leave it and try to do better next time. That is if you can live with something like this. I know that some people can't.

Josh
Author:  Pete Licis [ Mon Jan 09, 2006 5:20 am ]
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This one's for me, Josh, but I don't want to leave it as is because there are other finish problems (due to my stupidity) besides the mysterious one posted here. If you add up the sum of the problems ... it wasn't hard for me to decide to fix/redo it.
Author:  burbank [ Mon Jan 09, 2006 5:27 am ]
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Great sleuthing, Pete. Thanks for sharing.

Pat
Author:  Shane Neifer [ Mon Jan 09, 2006 5:37 am ]
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I have been using a Vermont America router pad, you know those pads that allow you to rout wood pieces without clamping them down. These pads are just a soft meshed foam and I really like it. Available at any hardware store for about $10.

Shane
Author:  Mario [ Mon Jan 09, 2006 5:47 am ]
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Eeeeeeeeeeek! Shane, no!!!!!!!!!

There, did i get the point across? <bg>

If that pad hasn't caused you trouble yet, it's just a matter of time. There are tons of plastisizers in them to keep them soft and sticky, and they can, and will eventaully, negin to eat at any finish left on them for any length of time.

They seem like good ideas, but they bad, bad....
Author:  Bobc [ Mon Jan 09, 2006 6:40 am ]
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Pete I would be tempted to wipe down with alcohol and try respraying.
Author:  Alan Carruth [ Mon Jan 09, 2006 8:11 am ]
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Shane:
What Mario screamed....

I used to use one of those pads.....
Author:  Dave Rector [ Mon Jan 09, 2006 8:55 am ]
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Shane, listen to Mario and Alan. I had a problem with one of those router pads once myself.
Author:  Terry Stowell [ Mon Jan 09, 2006 12:19 pm ]
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Years ago I had a ditto, but mine lightly buffed out. Whew
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