Official Luthiers Forum!

I'm going to use KTM-9 for the first time this weekend, had a few questions beforehand.

How much KTM-9 do you use in the spray gun for each days application(4-5 coats)? 1/2 cup enough?

Do you need to empty and clean the gun between coats, during each daily session, or just leave the gun alone and spray as needed(every hour or two?)Of course I'll clean after each day's use.

How fine(which grit) do you sand to before starting the first coat/session of spraying?

I've read about beginning each day's spraying with a light coat of DA before the KTM-9...is this instead of sanding or do I do both? Would sanding alone be as effective?

I've noticed some spray the guitar with the nech attached some unattached...any thoughts on this subject?


I do have Robbie's DVD and I printed some instructions from LMI's site for KTM-9 application, so unless I really missed something these are questions that just were not real clear to me, Any help would be appreciated.

Thanks,
Greg

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Gwaltney Guitars

Greg,

KTM-9 will produce great results if used properly.
You can find the Mike Doolin write up on KTM-9 under the Online Resources here at the OLF.

1. Spray lightly
2. 4 applications a day should suffice (too muck will leave a milky hue)
3. I sand with 400 or 600 between days and lightly wipe with denatured alcohol.
4. For the day's use I leave the KTM-9 in the spray gun and then after I run it through with DA and leave the alcohol in till the next day.

Make sure you thin out the KTM-9 with a little DA and filter it through a good coffee filter of some kind before spraying.

Best of luck,peterm38891.7740046296

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Peter M.
Cornerstone Guitars
http://www.cornerstoneukes.com

Will a paper type coffee filter work?

Greg

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Gwaltney Guitars

Greg, here's Mike Doolin's instructions.

KTM-9

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Peter M.
Cornerstone Guitars
http://www.cornerstoneukes.com

Don't wanna hijack the thread, but I'm curious -- does anybody here apply KTM-9 with a brush? If so, what were the results like?

Best,

Michael

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Live to Play, Play to Live

I used a spray gun at first but lately have done all with a brush.... It flows very well, no need to thin it out, its very forgiving and allows for any runs to be sanded away...

just gotta make sure to apply a VERY thin layer!

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Peter M.
Cornerstone Guitars
http://www.cornerstoneukes.com

Michael,

I have applied it with a foam brush and a very good china bristle brush. It was very hard to level. I think next time I'm going to try the method Pat used and got great results with...thin it with DA and pad it on with a flanel wad.

Maybe if I had cut the KTM-9 a little bit before I brushed it I would have had better results. I don't know. My results also could be attributed to inexperience.

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Joe Breault
Merrimack, NH
Perpetual novice

Peter,

If I might ask a follow-up question -- can you comment on your brush of preference? I have a qt of KTM-9 and bought a Purdy 1.5" nylon/polyester blend brush (for all paints, it says on the packaging), which I plan to use for the KTM-9, once I suck up the courage.

Also, can you be more specific about how you go about applying thin coats? (I'm wondering if I might inadvertantly put it on too thick) And do use anything as a sealer or pore filler before applying the KTM-9?

Joe, thanks for your perspective. I'm a newbie as well when it comes to applying finish with a brush, which is why I ask. All my experience is with french polishing.

Best,

Michael
Michael McBroom38891.918287037

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Live to Play, Play to Live

Michael, check out this link to the brush sold by Target Coatings . It also has a link on the page that will lead you to brushing techniques for waterbased products.   

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Don Atwood
Arlington, VA

Thanks Terry,

Do you end up using 80% of a quart per guitar, wow that sounds like a lot.

For those of you spraying one coat at a time, cleaning the gun adding more, and so on, how much KTM-9 does it take to do one coat. 1/4 cup?

Greg

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Gwaltney Guitars

The voice of experience for any finish: Practice on scrap, or you'll be sorry!!! Can I get a witness?

Greg, do you have experience with a spray gun?
if not, I strongly recomment using a brush instead.
Get a foam brush from a local hardware store and get a VERY thin layer on the guitar....its nice to try and get a nice thick layer on it but then you'll have runs and clarity problems....if you see any runs you can wipe it away with your finger, don't worry....KTM-9 can be very forgiving and will level sand anyway.... 4-5 applications a day, 24 hour dry time, sand 400-600, rub with DA, apply again....and so on.
I let mine cure for 2 weeks (to be safe) and then level sand from 600 all the way to 1800 and then buff with Menzerna.

peterm38892.0134837963

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Peter M.
Cornerstone Guitars
http://www.cornerstoneukes.com

I have two Craftsman HPLV (High Pressure low volume) guns. One is siphon and the other is gravity feed. I much prefer the gravity feed. It clogs less and and sprays more evenly, better control.

I have only sprayed KTM-9 with these guns and have done about5 guitars and two reso guitars. I agree with the above posts that suggest a little bit of DA like a table spoon per cup thinning. Also I highly reccomend some amber or other color akaline dyes. This makes the finish much deeper and natural looking.

I like John Grevens method of brushing on the 1st day and spraying on the second. Also I didn't catch what sealer you were going to try to fill pores. The sytem three epoxy applied with a squeegy(sp?) works great.

I used system 3 epoxy as a filler.

I've had some experience with a spray gun so I don't anticipate any problems there.

Do you guys spray with the neck on or off the body?

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Gwaltney Guitars

It is much easier to do them seperately so you don't have to deal with the build-up that happens at the neck joint and along the top finger board joint. Also buffing is a lot easier seperately.

Thanks so much everyone, I'll let you know how it goes today....I'm very excited to get this one done.

Greg

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Gwaltney Guitars

Greg,

If you buff by hand as I do,you will find that if you follow perfec it II with a product called Show Car Hand Glaze your finish will become even clearer.

Cecil

Thanks Cecil I'll give it a try, where did you find the "show car glaze" what brand is it?

Greg

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Gwaltney Guitars

Tapp Plastics has a great product called Novus 2

I've had no problem whatsoever using a foam brush with the KTM applied to the very tip only as shown in the photo below. The KTM-9 is used as is with no thinning. The key to avoiding bubbles is not only to avoid having a heavily saturated brush, but also by drawing the brush along the wood slowly. I've drawn the brush as slowly as about 1" per second. That said, I tried once to purposely to induce bubbles by drawing it across the length of the instrument in about 3 or 4 seconds ... and oddly, could not induce bubbles (contrary to my earlier experience). I'm not sure why so many people have trouble with bubbles.



Using this method, the finish goes on surprisingly thinly, almost as if it's squeegee'd on. Besides the obvious benefits, this has the side effect of not building up the large ridges you might get between adjacent strokes of the brush. Note that not much KTM-9 was used in six coats (see photo below). I believe the whole bottle is 8 oz.



While brushing requires more leveling than if spraying, it is easily done. And the results ain't bad either!



I've also tried padding it on, and this does yield good results as well. But, it takes forever! I did a test and found that with my relatively dry padding method, ten padding sessions led to a dry film thickness of only 1 mil! No wonder it took me 30-40 coats on a wood sample I tried.