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I still think this is a great finish for the body. But I am having my doubts for the neck.

Four necks have demonstrated finish "bumpiness" after long usage. Its really annoying to the hand, and I have already refinished two in nitro. Gonna do the same for the other two. I can't imagine another common denominator except hand oils etc.

Mike

Could you be a bit more specific than "bumpiness". Does it photograph? Worn through to the wood?
I usually put at least twice the coats on the neck compared to the back/sides.

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

Are you using epoxy for filler? I've seen epoxy "erupt" in the pores, sometimes months after finish, causing small bumps on the neck where there's been a lot of hand contact.

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

Yep, I had the same problem years back with Tru-oil over a Z poxy pore fill on several necks. Had to refinish them. It was kind of a bumpy fuzzy thing.

It has been discussed here several times in the past.

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It's not what you don't know that hurts you, it's what you do know that's wrong.

Is it limited to Zpoxy, or is it an issue for epoxy in general? I just put Silvertip on a neck and body, and it would be good to know if I should be concerned.

Yes I used zpoxy. Never had problem with EM6000 or nitro.

All in all, I would say I am done with Endur-Var. Its not repairable. Then, this.

This arrived for repair a couple of weeks ago. The 7+ year old finish is EM6K over zpoxy. Pat’s description of ‘epoxy blisters’ is pretty perfect, though the finish is only damaged where there has had skin contact. The rest of the instrument looks near perfect. The neck being the main problem, I removed all of the old finish and came back with Ecopoxy. We will see how it holds up...

I switched to Silvertip 2-3 years ago. Up until recently I’ve used EM6K over the Silvertip. I’ve since started using Endurovar and I really like the stuff. It’s much harder than the Target product and there is no dreaded blue cast from the acrylic base.

M

Thus, I am done. Nitro tried and true. Repairable.

Michael - Can you tell if the problem on that neck was due to the Z-poxy itself or due to the EM6000 on top of the Z-poxy?

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Once in a while you get shown the light in the strangest of places if you look at it right - Robert Hunter

I think it was ultimately the zpoxy. It was very soft and required scraping to get it down to bare wood again. The finish combo loaded up sandpaper immediately, so I also suspect that skin oils may have been a big part of the problem. I’ve seen nitro turn to cheese under some peoples hands.

I use epoxy to pore fill the back and sides of the guitars I build by laminating veneer to even out "bleed through", but have never used it on necks. For necks I generally "self seal " with whatever topcoat I am using by spraying additional coats and allowing it to cure before leveling. For those that don't laminate backs and sides the old fashioned oil based pore fillers might not be a bad way to go for pore filling under waterbourne finishes. I usually self seal non-laminated backs and sides also. It uses more finish, and takes more time to cure before it can be leveled and buffed but is easier. Endurovar when brushed builds quickly, so a couple of extra coats might be all the "pore filling" you need.

Jay, I had the problem with zpoxy under spar varnish and FP. Since switching to Devcon, no problem under FP.

I also had the problem where there was skin contact, but never determined if it was from sweat or heat.

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

This is an epoxy issue, rather than a topcoat issue, and the reason why my former boss went to Silvertip for filling. He saw finish bubble-up and separation in nitro, 2K urethane, and another waterborne finish over Z-Poxy, despite meticulous preparation and a compatible sealer/tie-coat with nitro. From what he could determine, all of the failures requiring repair (three neck refinishes, four full instrument refinishes) were played by men that claimed to sweat extensively while playing...male sweat tends more toward acidic than women, and an acid/base reaction at the epoxy/topcoat layer was thought to be the culprit. None of the finishes we use, and particularly not in the thicknesses we see in finished instruments, will prevent eventual passage of water and water vapor. Any degree of reaction between amine salts or other epoxy additives/cure byproducts may be a finish repair event waiting to happen.

Z-Poxy is not a blush or bloom-free epoxy, and the 1:1 mix ratio requires additives to the hardener which may play a role in the lack of stability and eventual expansion out of deep pores seen by some builders. Further, John Greven has been finishing his 60-70 instruments per year with Enduro-Var for at least the last 6 years using System3 Silvertip as a filler (a bloom and blush-free epoxy) without issue.

Having striped an EnduroVar'd neck in preparation for a customer-requested recarve (guitar was ordered with a deeper profile than standard...two years after delivery, back in for reshape to standard profile), the finish was tenacious...even the aircraft stripper we used (triple the methylene chloride content versus the now-banned MC-based consumer-grade paint and epoxy strippers) required 2-3 applications.

Even if moving back to nitro, a switch to a better, non-blushing epoxy might be a good idea. We found Silvertip to cost about the same per guitar as Z-poxy, did not age-darken as Z-Poxy hardener does, and the water-white color did not add that variable degree of ambering which can be an issue on timbers which tend towards the olive/green side of the spectrum, or on holly or other extremely light binding.

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For the times they are a changin'

- Bob Dylan

OK, so what I am hearing is, use some other epoxy than zpoxy? I am going to call in another guitar that used em6000 to check this

I’ve have got 4 fails that I’m aware of using Zpoxy and EM6K, 3 necks and 1 that needs a complete refinish. They are all over 7yrs old.

M

Yes, but the rest of the message is: switch to Silvertip in particular.

Or not.....
Most of the finishers I have worked with are reluctant to change the products they use once they find something that works for them.
Although Nitrocellulose lacquer is a "failed finish" many of us still use it because it is easy to apply and easy to repair and it fails far enough out in time that we don't have to deal with it.
Someone mentioned that most top coats are somewhat pervious to moisture. Epoxy is fairly waterproof. Could someone's sweaty palms be transferring moisture through the top coat to the surface of the epoxy which doesn't allow it to be absorbed by the wood of the neck?

I had two finish failures when using Z-proxy that looked exactly like Michaels picture. I believe one was with EM6000 and the other might have been lacquer. Certainly not a fun circumstance.

I second moving away from Zpoxy and use Silvertip. Works well with Endurovar. Endurovar finishes are fantastic and hold up. The spray and cure process is a bit of a challenge, but once that is mastered, it is a great finish - high clarity, no blush, thin, highly resistant to acid (perspiration), easily repaired with CA.

Lacquer and french polish will not survive people with acidic perspiration and a lack of cleaning the instrument after each use. Endurovar does far better in this regard. The nice part about switching from Zpoxy to Silvertip is that none of your process changes. One also benefits from a more neutral pore filler (Zpoxy having an amber cast).

Recently I have been shooting Endurovar straight over wood, as a pore filler. Initial experience has been very positive. My most recent examples were on Spanish Cedar and Koa, both porous. No grain filler whatsoever. Initial several coats of Endurovar, wait 48 hours to set, sand back. Then shoot top coats. Both fill and adhesion work well. One piece of advice with Endurovar: after shooting all top coats, come back in 48 hours and coarse sand (400 wetordry used dry - never water with Endurovar) to level orange peel. Then let the finish cure for final processing. It is far easier to sand the finish when set but not fully hardened. Then once cure, finish the sanding grits and polish. I found this approach to significantly reduce the sanding activity, by maybe as much as 50%. Endurovar eats paper for breakfast.

HVLP gun cleaning is so so. But a $15 Harbor Freight HVLP gun will do the job well, as opposed to using the high-dollar Fuji setup. This kind of finish doesn't have any material benefit to fine HVLP equipment. Clean the gun and, if not happy, throw it out and get another $15 gun. Endurovar finishes with a $15 HF gun have rivaled the finest finishes I've sprayed with the Fuji and nitro lacquer. Endurovar just a very different finish process/animal.

I will continue to shoot Endurovar as both filler and top coat, as I see no reason not to at this point - adhesion is tenacious, finish is rock hard, no compatibility issues with a single product, ease of process, no amine blush concerns, and less epoxy use in the shop.

I think I'm going to have to try Andy B's suggestion and try EV for pore filling.
I'm in UK and Silvertip seems to be unobtainable here (I've been trying to find it since I first heard of it) - as are most water clear epoxies, something to do with regulations?
I might question the drying/cure times but they're temperature dependent- GF says 1 week to dry, (and it seems to shrink for at least 4-5 days) and total 4 weeks to cure.

_________________
The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.