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Hi

I will be applying the first coat of KTM9 on my martin OM kit thsi weekend, I am told by my supplier that I have no need for filler if I am brushing on to Mahogany.

Should I treat the whole guitar it with one coat of shellac first ?

Regards

John

It's true you have no need for filler, but mahogany is a porous wood, so if you want a smooth finish, you will need to use a pore filler.

You can go several ways with filler. Z-poxy is often used, which has a minimum color impact. Colored fillers, such as LMI's micro-bead, can be used if you want to darken the pores. I believe there are previous posts here about how to use them. One suggestion, if you opt for a color fill, is to first put on a wash coat (thin, 1 lb. cut or less) of shellac to prevent the filler from staining the wood. It provides more contrast, so the pores are more distinct, a look that some like.

Pat

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formerly known around here as burbank
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http://www.patfosterguitars.com

i brushed KTM9 on my first guitar, thats the only experience i have. i applied a sealler coat of shellac and then pore filled with LMI micro bead.

i would definitely recommend a pore filler over mahogany and shellac is great for a seal coat.

hope that helps.

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sweat the small stuff.

IMHO, yes (no wax).

I would keep everything water based but I guess shellac would be ok. I just don't see the point. Just do a 'wash' coat with the ktm. I never had much luck brushing on ktm. I'd like to hear how it works out for you. The biggest issue I had was burning through on the wet sanding.

Same as the others, I would fill first. I like epoxy pore filler, but I don't a shellac sealer coat with it. Brushing KTM-9 takes some skill to get decent results. It takes some practice to brush it on without bubbles, drips or ridges. I have tried both foam and regular brushes. Neither seems to offer a significant advantage for me.

Before you do the final wet-sand, let it cure for a while. I let mine hang in the shop for a week or so to let the finish get good and hard. It seems to make the sanding go easier. Someone already mentioned burning through while wet sanding. I have one guitar that I had to sand the back down to the wood and re-finish 3 times because I burned through while finish sanding. Its hard to do a touch-up repair without getting witness lines. The stuff definitely has a learning curve.

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53% of all statistics are made up on the spot
http://driftwoodguitars.blogspot.com/

Would you say spraying definitely is an advantage with KTM-9 then ?

IMHO brushing should only be done if you dont have a spray rig. thats the ONLY reason i brush. as soon as im set up to spray, ill burn my brushes. there is, of course, a learning curve to everything. spraying is no exception. i dont know if there is anyone who would tout brushing a guitar finish as being superior to spraying. i got a decent finish brushing, but it took a ton of sanding and reapplying finish because i burned through over and over, just as others have mentioned. the finish will go on thinner and smoother if you spray. that is, if you know what you are doing. in short, spraying is better, but you can get a good finish brushing, its just going to take some care.

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sweat the small stuff.

I have shot 10 guitars with KTM-9. I would also recommend spraying over brushing. I also use a wash coat of shellac prior to pore filling. If you don't pore fill, you'll have to spray a ridiculous # of coats. I use the micro bead pore fill and gotten decent results. We do one coat per hour for 7 hrs, abrade with 400 grit the next day, and shoot 7 more coats. The last few we add a little everclear to the mix for the final few coats. This seems to smooth out the pebbling and make wet sanding a little easier. We then let the finish harden for approx 7 days. According to Mike Doolin's article (when he used it, that is) you can hasten the hardening process with warm dry air. Heat lamps and the like. We did that with a couple 200 watt bulbs in the drying area and it did help.

Regarding the shellac. The head luthier in our shop is convinced very good quality de-waxed shellac flakes and "fresh" shellac is key. I've read on other forums where folks had problems with adhesion, and the consensus was it was at least in part possibly due to the canned off the shelf shellac used.

My only complaint with the finish is I'm the one doing all the wet sanding (we're looking at pneumatic r.o. sanders). If you go this route and use silicon carbide cloth backed abrasive (micro mesh) use 1800, 2400 and 3200 grits. From there you can go to a "fine" wheel and skip the medium, which I find a little to aggressive. It takes a while to chase the sparkles, while wet sanding, and get rid of all of them, esp if you have any low spots. This is where there is the greatest hazard of sanding through exists for me. If you do sand through, flatten everything with 600 grit dry( We use 3M's purple premium paper.) and do another wash coat of shellac. We skipped this step and had contamination from the SC in the micro mesh. (We think)


Also I know micro mesh lasts a long time, but if you're not making any progress, get a fresh piece, and be extra careful with the binding and any sharp corners (headstock area, or diamond volute if you have one on the neck.

Good Luck! Anyone else have any experience (or tales of woe) with this product?

I don't have a spray rig, so I can't say. Spraying is probably faster, but I can't justify the cost of buying the equipment. You can get a good finish with KTM-9 but takes some work. Then again, the other types of finishes I have tried also have a learning curve. I think the trick is to pick one and stick with it until you get good at it.

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53% of all statistics are made up on the spot
http://driftwoodguitars.blogspot.com/

Thanks for all the tips, I have suspended the application of the KTM9 whilst I re consider.

I don't want to go to the expense of buying more kit however I have seen budget systems for as little as £100.00 ($150.00) - I would be interested to know what level of investment is required and technical specification for a decent spraying rig.

I'll start a new post.

Regards

John

I think finding one and sticking to it is the best advice too. I still brush finish on but I like the SM water based stuff better now. I let my guitars hang for 3 or 4 weeks and never burn through the SM water based stuff like I did with KTM. I still got good results with KTM though. Just don't be tempted to lay it on real thick and I know they say to brush it on and just leave it, don't fuss with it, but I found painting it over and spreading it out, IOW fussing with it, to work better. IF you lay it on too thick it's better to go ahead and spread it out.

I gave up on KTM-9 when I started getting guitars back with blistering finish. Some folks chemistry, including mine, cause it to develope nits of cyst like nodules. The neck on my main player guitar feels like it's embedded with sand. I've switched to KTM-SV and so far I really like it, it feels way better and buffs out even shinier. I got a near perfect finish on my second try. I'm painting two more today and tomorrow. And for what it's worth, I used Preval sprayers for about a dozen guitars and found it better than brushing. In fact that's what I'm using presently to spray my shellac sealer coats...not as good as a real spray rig of course...

I use EM 6000 with a brush, and I get pretty good results. Not as good as I'd like but I get better with each one. I've found the type of brush makes a big difference. I've got the highly touted Davinchi brush from Target, and if I don't overload the brush, and keep it almost perpendicular to the surface, using only the tip I don't get too many bubbles or ridges. I've also found that alternating the direction I brush helps get it leveled better. I brush lengthwise on one coat, then crosswise on the next, then diagonal. i like to do a quick level sand with 800 after 9 coats, then I apply about 6 more. I go with 15, rather than the usual 12 that most seem to do, to make sure I have plenty of finish so I don't sand through. You can get pretty good results using a brush, but it take time and attention to detail. Good luck with whatever you try.

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Rob

Thanks for the heads up re sandy nits and the like. I had read a mandolin makers blog about KTM-SV and the positive results he gets. It is good to know for the future. I also agree with jfmkenna. It is better to stick to one finish for a while (Please note, I say this having used only 2, paranoia is relative) We are just now getting a handle on how to use it and how it 'acts.' The learning curve would have been MUCH steeper if it weren't for Mike Doolin's and John Greven's articles on the product.

One more vote for spraying. I've got a $50 HVLP gun and a Dewalt compressor - and it works fine. You need good ventilation, (although not an explosion proof fan) and a good mask. Even though it's not nitro, it's still not safe, so treat it with respect.

I'd definitely fill the pores, regardless of what method. I use Zpoxy, which works for me. (but also need to be very careful - epoxy hardener is bad stuff).

I've never brushed KTM9, but I've sprayed half a dozen guitars with it, and haven't burned through on sandback/buffing yet. Must be more of a risk with brushing.

I like the finish - and although my spray technique isn't professional, I find the finished product is fine. Ditto on the "sparkles" - frequently takes multiple passes with the 400 wet/dry and a warm dish detergent solution to flatten so that the sparkles are gone.

Good luck.