KTM-SV Waterborne Finish

[Darryl Young]

FYI, I thought I would share some thoughts about KTM-SV (spar varnish) from Pete Brown who posted the remarks on the ANZLF forum. Here is a link to the post and a couple of pictures of guitars he has finished with KTM-SV. For the record, Grafted Coating claims KTM-SV is “a waterborne, oil-modified, self-crosslinking urethane” so completely different than a water based, acrylic lacquer.

Here is the link:
http://www.anzlf.com/viewtopic.php?t=33 ... ight=ktmsv

And here are a couple of pictures of Pete's guitars finished with KTM-SV:

[John S]

KTM-SV has been the topic of much discussion over on the OLF:

http://www.luthiersforum.com/forum/view ... &sk=t&sd=a

http://www.luthiersforum.com/forum/view ... 01&t=22737

mostly as an alternative to acrylic-containing waterborne finishes such as EM6000, which some folks have said has a bluish cast on dark wood. If I recall correctly, Ken Casper has some experience with the bluish cast appearing and disappearing with time. I haven't used KTM-SV myself, but my impression from the above threads is that it might be a little trickier to work with than EM6000. Might be worth a try, though, as those who have used it are pleased with the results. I know that LMI carries it, but it's way more expensive than buying it directly from the manufacturer.

John

[Freeman]

Here is a beginner's first attempt with KTM-9

[Darryl Young]

Freeman, is that koa? It's gorgeous.

[johnnparchem]

I am on my third coat brushing on KTM-SV over Z-poxy + shellac sealer. It is really hard to brush on evenly. In fact after my first uneven coat of KTM-SV I almost sanded it off and switched to padding on qualasole for the back and sides. I decided to go on to see how it goes. I have been sanding it back with a 400 grit pad each coat which cleans it up and I do seem to be building up some finish. I think I need to get a sprayer and set up a place to spray. On the plus side the KTM-SV does not smell very much.

I am padding on a finish to the top with qualasole, I am have done about 8 light sessions. I love how it is going on.

Post note. I think I am starting to understand how to apply the varnish with a brush. I needed more varnish on the brush than I thought. Basically you need to float or flow on a film of varnish starting a few inches from one edge and then come back a few inches from the other edge still floating on the finish flow it to the other edge. Very few brush marks and the finish levels as it drys.

[johnnparchem]

PPS -

Thinning the KTM-SV with just a little bit of water, removed the last of the brush marks I was getting as the finish seems to self level. Now I am knocking off dust with a 500 grit pad, needing to do almost no leveling between coats.

Hopefully by tonight I will be finished.

[Darryl Young]

Awesome!!! Glad you figured it out John. What I see looks great......keep showing the pictures.

I'm stuck on figuring out how to pore fill the Luan panel with Zpoxy. Todd Stock told me he had built boats with Luan and it was so porous and drank so much filler, he thought it was more filler than wood! Ha. He recommended I ditch the Luan test and try EIR or something similar. I have a couple EIR back and side sets I've not yet used. The sides are 0.250" thick on one of them so I'm going to finish one of these sides as a pore filler test instead of the Luan (I can get rid of the finish when I put the side through the thickness sander prior to bending). I'm about ready to try the first coat this evening and I'm sure hoping it goes better.

[johnnparchem]

It took me 4 coats of z-poxy before I was happy with the EIR headstock veneer. What I am slowly learning is to have a good light on the wood, really work the z-poxy into the wood and pay attention to the very very small bubbles on the surface. If they are coming up there are still pores to fill in the area. While wet everything looks filled but when sanded the empty pores open right up.

[Darryl Young]

Is your neck mahogany?

[johnnparchem]

Yes it is a mahogany neck. The whole kit is from John Hall.