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Brad,

I've been using the Kovax stuff recently too on Simon's recommend.

I did use it in the epoxy pore fill process successfully. The first 1 or 2 applications I fill and then scrape/sand back with 220/320. But once I feel like I'm on the final application I'll squeegee it off and almost french polish it level with a shop towel to leave the thinnest possible layer. Then the 600 (mint colored) assilex sheet over a hardwood block to "level" (really get rid of little nubs from the shop towel) followed by red scotch brite. This has given me the best (and thinnest) level coat of any I've done. I'm using the silvertip epoxy.

When using it to level finish I use a hardwood block under it until I have completely leveled the finish after curing (usually with 1200). After that I use the softer supplied pad to move up through the grits to 3000 buflex. Sometimes I'll go to 5000 Trizact after that to cut down as much as possible my buffing time.

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Burton
http://www.legeytinstruments.com
Brookline, MA.

Thanks, Burton.

I got to use this stuff for the first time today to level out UV porefill and scuff between coats of UV topcoat. It might be the placebo effect, but I really liked the way it cut and seemed super fast and clean. I will order the 600, 800, etc... as my current supply of paper starts to run out.

I think EBay seemed to be the cheapest. $41.70 for 25 of the 170x130mm sheets.


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Been thinking about this a lot. I have seen some properly cared for guitars that are over 20 years old and the nitro finish looks good. Yes, it is a dead end. It will eventually fail.And I completely understand your safety concerns. And one day, the government may ban it. That said. Its the repairability that entices me. Not just over the long haul, but during the build! The other thing that attracts me is the ease of the build. And level. and buff. I agree, sending a novice off to work with this stuff is a recipe for disaster. But still...

Is your 2K urethane something you can spray and melt? For me, if the finish is cross linked and unrepairable, I'm out for now. The only waterborn that comes close it EM 6000. and it has its own set of problems. What the world of guitars needs is waterborn version of nitro. Any takers?

Mike

The closest we have gotten is some enterprising individual who has filed a patent for a non-existing formulation in the hope that one gets created, he will reap the patent rewards: https://patents.google.com/patent/EP0493842A2/en

HI Mike,
The truth is there is really no good finish -- and we are all just trying to find something that will work "the best" for us. The one great thing both nitro and shellac have going for them are the repairability and I agree it is a wonderful characteristic for a finish to have. You can repair this modern stuff but it is a real challenge to get truly perfect/flawless results the way you can with nitro or shellac.

I've been able to directly compare a black nitro neck that I had some local guitar finishers do for me against my own 2k urethane work. And I have to say, I don't feel like there is much comparison. The urethane is a much nicer material. The nitro feels grippy and tacky in comparison to the urethane which is fast and smooth. One of the things I loved about the varnish was the great tactile feel. Urethane isn't quite as nice but it's close. The other thing I was amazed at just how easy scratches develop in the nitro (the black really highlighted this issue). It is soft stuff and combine that with low solvent resistance and loads of people getting similar issues with sweat clouding up nitro finishes as does happen with French Polish. I think this is one situation where tradition gets in the way of progress. The nice thing about urethane is that it is an automotive finish and there is a massive industry built around repairing this stuff -- so it can be done. Ultimately, I feel like my customers are getting a much better product with the urethane. It is just durable enough that general handling and decent care will keep the guitars looking great. Nitro (like French Polish) just requires more care and eventual maintenance. I'm not saying nitro isn't a good finish -clearly, it is most certainly a suitable guitar finish -- but I do think that in every regard except for repairability, the urethane is a vastly superior product. Polyester goes in the opposite direction - for a guitar top, I think it is too hard.

Lastly, I think it is also important to stick with what you are comfortable/good at. Finish work is a PITA -- and it is important to be able to get the instrument nice and shiny and DONE.

Is this stuff safe to use in a basement with a window fan?

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Hutch

Get the heck off the couch and go build a guitar!!!!

It is VERY nasty stuff. As long as you can remove all of the overspray and clear your room -- then you are okay. It really depends on your window fan. I'm using a ventilation fan and it really moves some serious air. With nitro or any of these modern catalyzed finishes -- you need enough air movement to basically empty the air out of your room. With nitro, you also really need to make sure everything is explosion proof as well.

Pay attention to my original posts in this thread as it explains what I'm doing. I'll be spraying again in about 1 week and I'll document things a bit better for you guys - including the buffing process. I may implement a small rotary buffer as well. Automotive clears respond well to this type of buffing.

If anyone wants to call me (386.444.9790), I'm more than happy to help (leave a voicemail and I'll call you back). Figuring this finish stuff has been a nightmare for me - and if I can help anyone else not go through the same stuff I did, then I'm glad to help.

One last reminder, do not take this stuff lightly -- ensure you have proper safety or don't use it. The nice thing is that so long as you have a workshop area - you should be able to at the very least, duplicate my safety precautions.

It's not flammable is it? That would be my main concern. I'm sure I can get a strong enough fan to keep the room clear. Does it stink while it's curing, that's another big concern.

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Hutch

Get the heck off the couch and go build a guitar!!!!

All of this stuff is flammable but nitro takes things to an entirely different level !!! I have a water heater pilot light on in my shop as well as regular lighting while I'm spraying -- and I feel perfectly safe. I do have an explosion proof fan tho'. Yes, it does have a strong smell. Read my first few posts about duration and how I handle this.

I have a pretty good home spray booth setup with a powerful explosion proof fan and adjacent windows to bring in make up air. I have the Axiom charcoal air filter running full speed during the entire spray schedule. Even with all that, and running the fan the entire time I’m spraying, and letting it run while the solvent flashes off, it’s still not 100% undetectable upstairs.

If you are spraying inside your home a simple fan will not be enough to cut down the smell in any reasonable way. Setting aside whether or not it can clear the overspray, which it probably cannot.

Sorry to be a wet blanket.


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100% agree. And I would especially emphasize two things. First, if you can smell it, that means you are exposing yourself to it. Second, as bad as it is for you to expose yourself to nitro, catalyzed finishes are, to quote Keb' Mo', a whole nutha thang. Catalyzed finishes are very dangerous while you are mixing them and spraying them. Do everything you can to avoid exposing yourself. "Fans" just won't cut it. Go big or don't do it.

"Finish work is a PITA" No truer words have been spoken.

Simon, I would caution you to steer clear of automotive urethanes as they have no place on a wood instrument. Automotive finishes do not have enough plasticizers in them to allow the finish to flex as the wood moves. Metal substrates have have a minuscule amount of expansion and contraction movement, as compared to wood, which don’t require the automotive finish to flex as much as required in a quality wood finish.

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tim...
http://www.mcknightguitars.com

Simon can respond for himself, but just to clarify, I think he said he was using Cardinal Luthierthane, which is formulated by Cardinal for covering stringed instruments made out of wood. He (Simon) has described this as being like an automotive finish, meaning (I think) that it is a two component type catalyzed finish. But the point is well taken that a person wanting to experiment with two component finishes should look for one that is formulated for covering wood, not one that is formulated for covering metal or fiberglass.

Well, I'll be interested in how this turns out. I went to cardinal site to checkout the product. Have you tested for repairabiltiy? Some products retain it for a while.

How many coats, time between, etc.

Mike

Tim is absolutely correct and is the guy I've turned to for a lot of help on this subject. I do know that a number of folks have success spraying automotive clears on solid body guitars but I certainly wouldn't consider anything that wasn't designed to go over wood -- and more specifically, designed for the musical instrument industry. There are too many good options and this finishing is too hard to use a lesser alternative.

I will be spraying the SimTec Urethane clear next time. (57x1 urethane clear and 58x1 isolante). SimTec supplies Taylor, Fender and a few other large players in the industry.

ICA, ILVA, and McFaddens are the only other companies I know of that make a urethane and sealer designed for exotic wood/musical instruments -- although, I'm sure there are others.

HI Mike,
Check out my first few posts - but basically, you'll need to follow the mfg's instructions regarding recoat time.

But basically you,

Seal
Porefill
Seal
3 Coats of Urethane
Sand back completely level. Surface should be absolutely perfect.
3 Final Coats. (only 2 for the top)

I'm going to spray a test panel next go around -- specifically for testing out repair methods.

Just a factoid about automotive finishes: Bob Ruck used an acrylic urethane topcoat made by Metalflake auto finishes called "Crysta-Cryl". I don't know if his later guitars were finished with this. But in conversations I had with Bob in the 1980s he told me he had been using this finish for decades and even called it a "miracle finish". He told me he successfully sprayed in his basement in the dead of a Wisconsin winter and ice cold air rushing in. It does not appear to be available anymore.

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Stay with the happy people.
--Reynolds Large

Back when I was in Charles Fox's Earthworks class in the 70's, he was using Ditzler automotive acrylic lacquer. The guitar I built there has held up fine on the finish--a bit of extra sinking in the pores, but that's probably more due to the filler than the lac. At any rate, I haven't had any cracking, delaminating or anything like that happen in well over 40 years.

Dave

I've been out the finishing game for a bit, but from what I know there are different attitudes (shown in various formulations) about automotive finishes...

some are real hard, very scratch resistant (though that usually comes as a trade off for the fact they chip easier when hit by road debris flying around) and "durable"...but when a fender is dented the paint will usually shatter and flake off

others are softer, scratch easier, and chip less...when dented the paint will many times stay intact and "flow" into the damage...

point being, being "specially made for stringed instruments" may mean squat...there may very well be a better product around for one's specific needs and desires