Official Luthiers Forum!

Has anyone ever tried to I/R cure their KTM-9 finish? I'd like to know how to tell if it's ready for sanding and buffing, how long to leave it under lights, terrible technical difficulties etc.
Any input would be most appreciated...
Thanks

Infrared? Do you mean bake it like a Buick? Could you be thinking of UV? KTM has a forum of sorts, did you look there?

Dan

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Dan
http://www.acme-archtops.com

Hi!
No, I mean infrared, not the industrial UV typical for poly. Grafted coatings has told me that hardware store I/R lights will do the trick, held at least 16-18 inches from the surface. I'm uncertain as to whether it is the light or the heat that does the curing. On their site it indicates that the cure happens from the inside out, which makes me think that once it's dry to the touch from I/R it should be ok to sand and buff, but I wonder if anyone here has experience with this method.

Yes I have done it keep the Ir light 24" form any point on the guitar. Check the surface temp often. You will need some way to rotate the guitar continuously to avoid over heating. High risk of bubbling. Now the real question is with a 7-10 day cure-out, why risk it?

Just to know the limits, especially for repairs, really. For the curious, I found that I/R dramatically reduced between coat times, but did not cure it to final hardness ready for buffing.

Hey, Fool

This is very interesting to me, because I've about hit my limit with nitro, and anything that moves the work out the door seems like a good idea. I'm close to using KTM for the first time, and I wonder if you could expand on your finishing schedule.

Dan

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Dan
http://www.acme-archtops.com

Hi!
Day one, epoxy pore filler
Day two, pore fill second coat. I scuff with a 3M abrasive pad between coats, not with a power sander of any sort. I found a blotchy effect quite easy to achieve due to the amber tone of z-poxy. If the thickness varies from spot to spot it tends to show, so I apply it very carefully and only scuff it with the pad to scratch it enough to take paint. I would use sysem 3 but LMI won't ship it north of the border anymore...
I built a sort of frame to hold the bulbs, one above, one in the middle, one below. The top and bottom ones are at 45 degree angles, not straight up and down. I hang the body from the dovetail and spin it by hand. The whole process is still an experiment for me, so have your salt cellar ready for a good shake or two...
Basically, I just spray the body with a super thin coat and hang it on the rack, then paint the neck by which time the body is dry, then do the reverse and do it again and again and again and again and again....once I have a good founadation I sand completely flat with 220, then repeat until I'm certain I have enough paint on it, then I forget about it for ten days to two weeks. I found the I/R did not speed up the overall cure time, but sharply reduced the between coat time. So basically I spent about six hours doing nothing but spray, switch, spray. Honestly I'm not at all sure it's worth the bother. And for what it's worth, I'm not going to use KTM-9 anymore, as the only guitar that I've kept that has it is failing miserably everywhere it touches my skin. It bubbles up and becomes speckled like brail. I shudder to think of the 20 some odd guitars out there I've made with it. Somewhere there's a thread with other people having the same problem.

Dan,
I've finished four guitars in KTM-9. The last two I've French polished and this seems to be a superior finish in my opinion. I've also been testing Tru-Oil on scrap and this is looking very good. At this point, I would recommend either of these finishes over KTM-9.
Pat

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There are three kinds of people:

Those that make things happen,
those that watch things happen,
and those that wondered what happened.

Hey, Fool, thanks for coming back. Blotchy with the zpoxy, eh? My experience with West and Sys3 (boatbuilder, about a hundred gallons) showed that the second coat always evened things out, and even then the first coat usually looked fine. The literature, and my experience, led me to wipe down the cured epoxied surface with clean cloths and fresh water, to remove AMINES which developed during the cure. Does anyone do this for zpoxy? Is it a problem with zpoxy? Because this waxy excrescence was minor trouble between epoxy coats, and potentially major trouble under paint topcoats.

Regarding the apparent fragility of KTM, I'd like to suggest that the IR forced drying might be the culprit. Consider: the film seems dry, it's firm to the touch, but is all the free water out of the previous coat? Has an impermeable skin developed, much like force-dried lumber, where the top layers of cells "tighten up", and prevent the free flow of moisture trapped down in the body of of the board?

At least, I'm hoping the KTM is tougher than I fear.

Because, Pat, I'm working on an archtop bass right now with color on the body, and I'm hoping to find a clear topcoat to protect the color with. I'm with you on the FP, and I can see using it over the color....Jeez, it's gonna be forever before I get this thing on the road! My original plan was to topcoat with brushed KTM, but I can see issues with block sanding and buffing...but superblond FP might go on with a minimum of agony, including color issues.

I hope someone will ring in with an opinion about the blotchiness. How about a sealcoat of dewaxed shellac, maybe 1/2 lb cut to set the color?

Thanks, Dan

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Dan
http://www.acme-archtops.com

Hey, Fool, thanks for coming back. Blotchy with the zpoxy, eh? My experience with West and Sys3 (boatbuilder, about a hundred gallons) showed that the second coat always evened things out, and even then the first coat usually looked fine. The literature, and my experience, led me to wipe down the cured epoxied surface with clean cloths and fresh water, to remove AMINES which developed during the cure. Does anyone do this for zpoxy? Is it a problem with zpoxy? Because this waxy excrescence was minor trouble between epoxy coats, and potentially major trouble under paint topcoats.

Regarding the apparent fragility of KTM, I'd like to suggest that the IR forced drying might be the culprit. Consider: the film seems dry, it's firm to the touch, but is all the free water out of the previous coat? Has an impermeable skin developed, much like force-dried lumber, where the top layers of cells "tighten up", and prevent the free flow of moisture trapped down in the body of of the board?

At least, I'm hoping the KTM is tougher than I fear.

Because, Pat, I'm working on an archtop bass right now with color on the body, and I'm hoping to find a clear topcoat to protect the color with. I'm with you on the FP, and I can see using it over the color....Jeez, it's gonna be forever before I get this thing on the road! My original plan was to topcoat with brushed KTM, but I can see issues with block sanding and buffing...but superblond FP might go on with a minimum of agony, including color issues.

I hope someone will ring in with an opinion about the blotchiness. How about a sealcoat of dewaxed shellac, maybe 1/2 lb cut to set the color?

Thanks, Dan

_________________
Dan
http://www.acme-archtops.com

Hey!
The guitar with the failing paint was not done with the I/R.

Blotchiness of color is not the fault of the Zpoxy or any other epoxy. I am not sure exactly what you mean. I have nearly 30 guitars that have been pored filled with Zpoxy not one would I ever say anything about the Zpoxy was blotchy. Sound more like a mixing, application or sanding problem. But then again I do not leave a film of zpoxy on the guitar. I fill the pores squeegee style with a safety rounded corner utility razor or a credit card. I scrape off all excess possible at time of application allow to cure sand back just to bare wood leaving the epoxy in the pores only. Make up a 60% alcohol/40% zpoxy mixture rag on just enough to wet the wood. (No noticeable film thickness) allow to cure 24 hours, scuff with 400p and seal with 1.5# cut of shellac.

From there I may use nitro, KTM9 or I may French polish

I too agree French polish is a better finish but not necessarily in scuff or dent resistance to KTM9. French polish is my preferred finish without a doubt but I have no issues with KTM9 or nitro. I can’t compare them because each is a different carrier/solid make up and provides a different type of finish.

In my opinion after 4 years of use now KTM9 is a great waterborne finish. It is not Nitro and it is not Shellac but It is in my opinion one of if not the better Waterborne acrylic lacquers on the market.

I would IR cure anything between coats, I have IR cured KTM9 after the final coat. but I think it is redundent to do so as KTM 9 will cure out in 7-10 days in most cases

Should have read:

I would never IR cure anything between coats, I have IR cured KTM9 after the final coat. but I think it is redundent to do so as KTM 9 will cure out in 7-10 days in most cases

I'm a KTM-9 fan. i like the low toxicity. That's worth a lot to me even if it doesn't buff like nitro. I have experimented with 7, 14 21 and 28 days. If I can be patient 21-28 days seems a harder and more durable finish. I think it buffs to a higher sheen the longer it cures . This summer I have put two guitars with KTM-9 in the sunlight where it comes into my living room. the sun's got IR, UV and more. I' let you know how it turns out. I live in BC which is like Pacific NW, so the sun trick may not be a year round technique.
I saw on an earlier thread that some sand their epoxy pore coat back to the wood. I haven't done this (deliberately), I have just 220 grit the "nubs" off (quote Mike Doolin. ). Then 3 coats KTM9. wait 7-10 days, 600 grit dry sand, drop fill if needed, wet down with wet cloth, rub dry and spray 3 more coats. I repeat process to 12 coats, dry sand (Random Orb) 600 - 800 -1000- 1200- 1500 - 2000 - 3000 - 4000, tripoli buff, and then Maguires swirl remover and hand or power buff again. I like the job it does.
Each guitar gets better for me. (Though I don't get that photographic mirror sheen like Hesh's black beauty.)

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Greg
http://garibaldiinstruments.com/

I have had much better luck with the Target URL product. It seemed to drip less, buff out easier and dosen't melt off or orange-peel when perspired upon.
It is also less expensive. On my last instrument I used their Hybrivar which gave a deep transparent amber-toned glow, allthough there were some spray issues.

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It's not the miles ahead, it's the stone in your shoe


In Markham,Virginia