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Matt,
Tom, Peter, and I have all had adhesion troubles using Zinsser Sealcoat. Rolfe has been fine but doesn't use oily woods and also doesn't need to peel off a section for a bridge.
Only the Ilva has been reported 100% successful.
Thanks. This thread has been particularly valuable to me so far.

JLK, thanks for the feedback that the zpoxy seemed to seal the rosewood fine. I'm going to test that as well. The semi-retired body shop neighbor of mine also seems to think the zpoxy would work fine as a sealer.

If we ignore the oily woods for a moment, what is an appropriate sealer for good adhesion on a spruce soundboard when applying KTM-SV?

By the way, I called Camger and ended up I was transferred to Gemni Coatings in Dallas and they carry the TF-25 Resin and TV-19 Hardener. The smallest quantities I could buy it are 1 gal of the Resin and 1 Liter of the hardener. I can get both for roughly $85 (total for both products). They were unsure if there would be 1 or 2 hazmat charges to have it shipped then add shipping......so it could be another $45-$65 to have it shipped to me. The zpoxy option is sure attractive compared to this cost!

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Formerly known as Adaboy.......

I look forward to hearing what Grafted Coatings comes up with as a solution. Nice to have them respond on this topic.

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Formerly known as Adaboy.......

I am working with various vendors of mine to come up with a possible sealer for oily woods - must be waterbased as we will not supply a hazardous system. Just finding out about this, this week I can only do so much.

KTM-SV is a waterbased urethane system for wood - self-crosslinked via air drying.
As with any product it’s always suggested to try a test piece to another product before you find out they are not compatible on a finished project.

Based on above, it’s hard to test every piece of wood species and product -- a lot is learned from what you guys perfect in the luthier world and what I see in the lab.

isolante sealer as someone stated above is just a term used such as "barrier coat" and is as generic as saying urethane.

With all being said, I am looking into seeing if we can do something to fix or help with this situation and will go from there.

As for Zinsser sealcoat working for some, and not others, and over various wood, that sounds like a wood problem in that the oils in the wood are *possibly* coming through the sealer and causing intercoat adhesion between that and the KTM-SV. It’s something I need to see verses just giving a true opinion on the matter.

Reading one post about us calling it Spar Varnish - been told in the past that it could hurt sales and use of the product - being true/false, it’s still a varnish or clearcoat or urethane finish. Play on words.

Thanks,

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Matt Lawrence
Formulator/Tech Guy
www.graftedcoatings.com

Hi Matt, and welcome to the OLF. Thanks for bringing your expertise to the forum.

My guess is you are aware that Target Coatings has a waterbased shellac which might be a good sealer for the KTM-SV, mind you it's not a KTM product..... I've not used the KTM-SV yet but I'd like to give it a try as I'm always looking for something to replace the Nitro that I'm using. Having tried the Target EMTech 6000 and found it still had the blue tint from being an acrylic lacquer, I switched back to nitro for the time being.

I'll keep watching to see if a suitable sealer is found/made for the KTM-SV and I'll give it a shot at some point in time.

Any chance you have a Canadian supplier of the product?

Cheers and Thanks.

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Don't try the Target shellac as an oily wood sealer. That's how I got in trouble with the sealer situation in the first place. I discussed this with an independent finishing expert, and he explained that the technology that makes shellac waterborne reduces its effectiveness as a barrier coat. Target may dispute this, but it certainly has been my experience. I like the Target shellac and still use it for shading since it mixes better than the alcohol solvent shellac with TransTints and Stew Mac's relabeled versions of TransTints. But after shading, I use at least two coats of Sealcoat as my barrier finish. Now, if y'all quite using those oily tropicals woods to build, your problems would be solved.

At the time, KTM-9 and KTM-SV are available throught LMI over at www.lmii.com or direct via us at our website.

I have some pieces of rosewood, cocobolo and ebony on order for trialing with our coatings and possibly sealers for oily woods, etc.

Until then, I will be formulating a few coatings and talking to more of my contacts in the polymer world that specialize in wood finishing - not necessarily oily woods but working on it.

Like I said before, this will not be answered overnight....The magical wand is low battery power.

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Matt Lawrence
Formulator/Tech Guy
www.graftedcoatings.com

I just finished a Brazilian rosewood guitar with KTM-SV over zpoxy sealled with home mixed shellac from LMI. I am having no problem with oil seaping in to the finish, curing or adhesion. I padded on the 2 coats of shellac. The z-poxy for the pore fill was sanded back to level each application, possibly to the wood in places.

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http://www.Harvestmoonguitars.com

Did you seal the spruce as well? How did you clean the bridge area?

Do you washcoat/seal the wood with shellac before using the Z-Poxy filler or after applying the Z-Poxy? I'm having adhesion problems on three Koa ukuleles using shellac (made from LMI flakes) then applying waterbase filler and sanding sealer then topcoats (StewMac). I haven't had this problem before. Is Koa wood considered oily?
Thanks for any help.
Bill

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Formerly know as Mandodiddle.

Bill,

I'm a little unsure, are you spraying KTM-SV as your final top coat?

BTW, I see you are from Conway. I grew up outside Morrilton by Petit Jean Mountain so I wanted to say hello (live in NW AR now).

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Formerly known as Adaboy.......

Darryl,

Nice to hear from you. Moved to Conway from eastern Arkansas in 1992 and I love it. What I am using all comes from StewMac which is based on Target Coatings waterbase formulas. The adhesion loss seems to be all the way below the sanding sealer coats, which is either at the filler/sealer coat interface or possible even below the filler (as sometimes I can see unfilled pores when the finish releases. I actually pulled a chunk of finish off yesterday with blue tape.

Bill

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Formerly know as Mandodiddle.

Bill, since this topic is mostly about KTM-SV, you would likely get more response if you asked your question in a thread of it's own. I know you likely would like ot have some feedback.

Weather hasn't been cooperating here but looks nice for the weekend. I plan to spray the SV over zpoxy on my test boards this weekend. Will spray some over SealCoat as well to test that.

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Formerly known as Adaboy.......

I am finding KTM-SV very unforgiving. Any mistake or burn through seems to mean that you need to respray the entire guitar. I am not an experianced finisher, my ability of getting to a finished guitar without of a mistake is appearing to be none.

In my lastest attempt I have the back looking nice but after leveling the sides first with 600 grit and then cleaning up the scratches with a series of 3m polishing papers from stewmac. I ended up with a half dollar sized area where I burned through a layer of finish. It is very noticable.

This weekend I will attempt to spray a couple of new layers as carefully as I can and level starting at 800 grit the following week. I will see how that goes. I am so close to sanding it all off and trying a different product.

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http://www.Harvestmoonguitars.com

John, how much time elapsed between coats of SV? Seems recoating within a couple of hours might be better and the other folks schedules show no more than a day before the second set of coats. Also, some use DA on the SV before applying the second set of coats likely to help adhesion of the second days coats.

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Formerly known as Adaboy.......

We are waiting for panels to come of the various oily woods. Lining up a few ideas, coatings for testing.

One way or another, we will have answers to this overall situation.

Have a great weekend.

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Matt Lawrence
Formulator/Tech Guy
www.graftedcoatings.com

I am puzzled by the need to spray the entire guitar for a small sand-through. Sometimes you will see witness lines all the way through various grits (I go down to 2,000 or 4,000), and then they disappear with buffing. If there is any finish where excess sanding has been done, it will buff just fine. When I have a serious sand-through all the way down to the wood, as I sometimes do on a corner of the face or sides of the headstock, I immediate brush a coat on the bare wood (after staining touch-up), and continue to brush a coat every hour with each coat overlapping the previous coat by 1/8" to 1/4". I'll do about four coats like that, sand it level CAREFULLY the next day and then go through the grits to get the scratches out. Worst case scenario is having to spray coats to an edge (like an entire top or an entire headstock face) on a surface with a sand-through, but if I do that, I'll always sand the entire surface with 800 and brush several coats on the sand-through area before spraying. Never an entire instrument for a sand-through.

Rolf,

Thanks for the information. I have only sanded through one layer of finish in one small place so I will go through the process of buffing out the guitar before deciding to spray again. Other than that one small area the finish looks good.

My fear was that it looks so noticable now.

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http://www.Harvestmoonguitars.com

John,
No offence intended but it may be your lack of experience more than the product. I found it very forgiving in application, asides from the aforementioned difficulties, none of which stem from the SV itself. I was surprised at how good I was able to make a shoddy spray job buff out.

I totally agree it is my lack of experience with the product. I have finish a guitar with nitrocellulous and I French Polished a classical guitar. Then I was able to build up a single layer of finish. Here I panicked when I polishing the side of what I thought was a great final coat and burned through in a small place. I did follow Rolfe's advise and buffed out the guitar and am happy with the result.

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http://www.Harvestmoonguitars.com

That's a beautiful guitar and great finish job!

great looking guitar.

for ha-ha's, how many hours total so far?

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Matt Lawrence
Formulator/Tech Guy
www.graftedcoatings.com

Thanks,

This is only my third guitar, I started in July. I have not counted the hours but there are a bunch. But as it is a hobby for me, the hours spent are what I am after. I learned a lot on this guitar.

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http://www.Harvestmoonguitars.com

I'm pore filling my mahogany neck with zpoxy. Put the second coat on last night. If I sand back to wood leaving zpoxy in the pores only, can I spray the KTM-SV right on the mahogany/zpoxy or do I need to spray a couple coats of shellac first? Based on the experience reported above, I could probably leave a thin coat of zpoxy and spray on that but I probably won't do that except on the rosewood headstock veneer. Here's a shot of the neck right after the first zpoxy coat.

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Formerly known as Adaboy.......

Darryl, I wouldn't sand back to the wood and spray KTM-SV. One, waterbornes don't "wet" the wood very well and two, you may have all the problems we've been talking about. You need some kind of sealer.

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Randy Muth
RS Muth Guitars Website
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