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I thought I'd share this as a potential problem for those who use or are considering using epoxy for filler. I have had epoxy react with my finish several years down the road. Attached is a photo of a section of neck, this finish was fine a year ago, this guitar is 5 years old. I just saw another one yesterday that's 3 years old and just started doing the same thing, bummer.
It could easily be me and I hope it is for the sake of those using epoxy as filler.
The finish is Epoxy filler ( either zpoxy or system 3),
McFaddens vinyl sealer,
Mcfaddens nitro.
I've seen this on four of my instruments so far to varying degrees, this is by far the worst. I stopped using epoxy filler a couple of years ago, so the the problems solved for me except for the repairs.
I just thought others might be interested in this too. I'm guessing it's some type of blushing in the epoxy.
Food for thought.

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Jim Watts
http://jameswattsguitars.com

I suspect what you are seeing is amine blush, albeit delayed. Your epoxy wasn't cured enough before you sprayed your sealer and top coats.

So, if following the epoxy pore-fill with FP, would that "amine blush" have the potential to occur? If so, how long do you allow the epoxy to cure before you apply the first finish coats (whatever the finish)?

I agree that it is probably amine blush that has caused Jim's problems but amine blush is not related to the cured state of epoxy when finish is applied. Amine blush is a by-product of the chemical exchange that is the epoxy curing process when sufficient H2o and Co2 are present in the atmosphere during, mixing, application, and curing of epoxy products. That by-product, named "amine bicarbonate salts" by some, and a host of alternatives of similar relevance to us by others, rises to the surface of the curing epoxy to remain a problem should it be painted over no matter how cured the epoxy becomes.

These amine bicarbonate salts 'sweat' onto the surface of the epoxy like a dew to form a sometimes waxy white, but more often, very thin clear oily substance. Unless you look hard, in this later form it can go undetected and will cause problems in the short to long term for most all finishes. If you do detect amine blush, do 'NOT' use abrasives to try and remove it as this only serves to spread the residue back into the surface. Probably the best solution is to wash the surface well with a nylon abrasive pad and lots of water to which a little citric acid or vinegar has been added.

The idea here is that this citric acid/vinegar solution will convert the oily amine bicarbonate into salt crystals that are easy to remove, but keep in mind that there is relevance to the argument that doing this can leave the remaining surface more prone to sorbtion of Co2 and H2o so you may only be removing the short term problem and still have issues down the track. I have a guitar finished with Truoil. The FB was glued on with Smiths Allwood Epoxy. Over the last 3 to 4 years I have removed a predominant 'ridge' which formed and has reformed at the glue joint of the FB to the neck on 4 occasions and that same ridge just keeps coming back...scrap it off, it comes back again and again.

To my mind the best way to avoid amine blush is to avoid using epoxy. If you just can't see yourself doing that, then you will need to understand more about this phenomenon so you can take precautions to avoid the cause.

READ THIS: http://www.huntsman.com/performance_products/Media/Blushing_of_Amine-cured_Epoxy_Resins.pdf

Here are four tips that may help you avoid amine blush.

1: To reduce Co2 sorbtion by un-cured epoxy, work outside. Doing this puts the product in the lowest possible ppm count of Co2 outside of a controlled environment.

2: To reduce Co2 and H2o sorbtion by un-cured epoxy, keep a fan running on you as you mix and apply epoxy. Doing this will keep the Co2/H2o being generated by your breath as you work from penetrating the mix. If you took the time to read the above pdf you will now understand that this is important because curing epoxy is a 'very' effective scavenger of those elements from the air so its just good practice...More importantly, keeping a fan running will keep epoxy 'fumes' from permeating through your skin to give rise in your potential to develop an epoxy sensitivity issue...you really don't want that to happen, if it does, amine blush will be the least of your problems believe me.

3: To reduce H2o sorbtion by un-cured epoxy, mix and applying the product only when the temp is on the rise and the RH is falling.

4: Good luck

Cheers

Kim

Jim, I quit using zpoxy a few years back after a similar condition appeared on one of my guitar necks. Just the neck only, How about your guitar? After reading about amine blush I simply stopped using zpoxy. I have not seen this condition since, but do not think that is conclusive, since it is only on the neck.

Chuck

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Jim,

Did you use epoxy as the pore filler on the b/s of the same guitars ? There seems to be loads of evidence pointing to amine blush but it's fascinating that the neck seems to be the main area that it appears on. Something to do with the smaller surface area/more radical curved surface area or continual interaction with hands?

I've stopped using epoxy and use egg white or pumice/shellac methods.

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Dave White
De Faoite Stringed Instruments
". . . the one thing a machine just can't do is give you character and personalities and sometimes that comes with flaws, but it always comes with humanity" Monty Don talking about hand weaving, "Mastercrafts", Weaving, BBC March 2010

I have experienced the same thing on an early neck - excellent, informative post - especially Kim's. Thanks all.

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"Building guitars looks hard, but it's actually much harder than it looks." Tom Buck

I had that problem along glue lines glued with Smith's All Wood epoxy. I have not had any problems using other epoxy brands as pore filler. ??

Mark

Heh, did not know about this. Thanks for the alert. From the little reading I did on the subject, cold ambient temperatures, high humidity, and increased CO2 are the promoters. Yet, if one allows a longer cure, then sands back to wood, this should never be a problem. For those leaving a thin layer of epoxy (for color or pop), you may want to wait longer then sand carefully.

Am I missing anything? But what is really weird is that most of you report this as a neck problem... suggesting that moisture from hands is somehow getting through finish and post-reacting with the cured epoxy. That does not match up with the literature.

Mike

Perhaps it is showing up on necks because of a chemical interaction with mahogany or ebony?????

I don't think it's moisture from hands. The problems I had were all the way up the neck to the body joint.... areas where few players handle the neck.

M

System 3 SB112 is amine blush-free. It's a little finickier about mix ratio, but I use a cheap digital scale and have never had any problems with cure. I like it.

The problem seems to on the necks only and it's in area's that don't get handled much also, ie the bass side of the heel. This is interesting that others have experienced this on necks also.
Mixing in high humidity is not something I have to worry about here in NM, we're in our wet season and it's a whopping 30% RH right now, it feels it too! I humidify my shop to 40%.
I've wondered about a possible reaction also with the Mahogany. It bubbles the finish too, in addition to turning grey.
I've also been using egg whites and more traditional fillers for the last few years.

The really bad thing here is it doesn't show up until years down the road.

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Jim Watts
http://jameswattsguitars.com

The problems I had took 10 to 12 month to show up. I refinished a couple of the necks and it showed up again in the same time frame. The only way I was able to fix the problem was to replace the necks. Needless to say, I quit using the Smith's epoxy and went back to gluing my fingerboards with Titebond. I have not had any problems since.

M

You know Mark, now that mention it I have seen a line show up at the interface of the fingerboard and neck too. I was never sure what was causing that, it must be the same phenomena.

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Jim Watts
http://jameswattsguitars.com

I just checked the MSDS on the SB112 and it is clearly an amine cure epoxy with aldehydes listed as a decomposition product.

While System 3s literature suggests that this is a reduced blush formulation, it is very unlikely that is is completely free of amine blush.

Another tip for reducing blush is to use fresh product. The precursors absorb water and CO2 every time the containers are opened, so those old tins you have back in the shop will have significantly higher tendancy to blush than fresh product.

-jd

FWIW, the literature states "Unlike many epoxy systems, SB-112 will cure to a clear, glossy, blush-free surface". I guess I don't know whether that means the epoxy will 'never' produce blush.

It's not just happening on necks. I have a Redwood topped EIR guitar that is showing the same phenomenon in the fill on the rosette (ebony and maple) and on the pore fill on the back. Oddly enough the sides are fine. The neck was filled with CA so that has no issues. Another guitar finished at the same time is showing no issues either. I suspect the mix rate of Z-Poxy is a bit more touchy than advertised (or I was a bit too carless). Since I fill each section at seperate times, it is quite possible I messed up on a couple of batches.

The thing I find most peculiar is how the epoxy seems to react with humidity. If the RH is high, I have bumps. Low Rh, sunken pores. I even stripped the finish refilled with CA and refinished to no avail.

Steve

A couple of points.

Amine blush is caused when curing epoxy scavenges Co2 and H20 from the atmosphere in sufficient quantity to cause a by-product of amine bicarbonate during that exchange. The amine bicarbonate then rises through the epoxy to deposit on the surface. It remains on the surface most times as a very thin watery substance that is much like silicone oil. Its occurrence and persistence is not related to how long the epoxy has cured. It does not evaporate and it cannot be removed by abrasion as this will only spread the problem to unaffected areas. The only relationship shared between the production of amine bicarbonate in epoxy and cure time lay in the fact that the faster a mix is cured, the less opertunity it has to produce this by-product during that exchange. This is one of the reasons why some commercial operations use ovens to accelerate the process.

All epoxies contain amines. Some formulations are sold as 'low blush' and do indeed contain less amines in their mix. However these formulations are also marketed as being highly resistant to abrasion, for use on decking etc. The reason is the trade off, less amines = higher MOE. For guitar builders this is not a good thing because these low amine formulations are more difficult to sand as they are more likely to ball up and clog the paper or scuff, even tear the surface rather than forming an even scratch pattern and sanding to a fine powder as high amine formulations like zpoxy will.

This phenomenon is not restricted to necks only. I have an EIR guitar that was zpoxy filled and finished with truoil. When I had completed that instrument, I was justifiably proud of the finish. It was beautiful and lustrous from the many hours spent 'burnishing' successive applications of truoil and it looked and felt fantastic. After the first month I noticed a few dull patches start to appear here and there. They were quite small at the time so I decided to let what ever was happening happen, and once settled, would repair as necessary. Over next few months I watched as the patches spread into each other and the finish rise to form rough ugly peaks all over the place...heart breaking.

If I was to hazard a guess as to why we are seeing more of this phenomenon occurring on the neck of guitars, it would be that we are probably more incline to leave more product on the neck. Particularly the heel where there is abundant end grain exposure to soak up the epoxy. I do not see this as related to any 3rd party exchange from the players hand to the wood. The back and sides being relativity flat surfaces are more easily worked during application and removal so perhaps this is reflected here.

Anther point bought up has been the suggestion that these formulations are perhaps more sensitive to mix ratios than we assume and this may explain why one area completed at one time with one mix had reacted differently to another area of the same instrument completed with a second mix at a later time. I do not see this as the issue. To me it is more likely that the RH had been different during each application, or perhaps there was a breeze of some other air disturbance which had reduced to Co2 count. Regardless they are the things we need to look more carefully at.

Todd has suggested that after years of using epoxy fillers, he has never experienced a problem with amine blush. This is completely understandable given Todd's capacity to do things in a methodical way. If his method addresses the issues of exposure to H2o and Co2, be that by intent or consequence, and he remains consistent in his method, then he would be more incline to avoid the issue, especially if he works in a location blessed with relatively stable environmental conditions.

The bottom line is that you can use epoxy as a filler without the finish being affected by amine blush. But to give yourself the best chance of allowing that to happen, you need to understand the cause and be confident that your process eliminates the potential, because if it 'does' happen, the only thing for it is to strip the finish, sand out the epoxy and start over.

Cheers

Kim

Anyone had problems with anything other than Zpoxy and Smith's?

Another difference between necks and bodies is most people leave a thicker finish on necks. Any possibility that the amine bicarbonate can escape thin films but not thicker ones?

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http://www.chassonguitars.com

I used Z-Poxy on several necks with Tru-Oil and they all got fuzzy within several months. Sanded back several times and it came back. Applications was under ideal conditions. There was a thinned coating of Z-Poxy for color on all of them. Now I use Mc Faddens fillers on necks with Tru-Oil.

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

This is from the System three epoxy manual

"Caution must be observed when using epoxy resins along with
polyester resins . Observe the general rule that epoxy resins may
be applied over cured polyesters that have been dewaxed and
well sanded but polyesters should never be used over cured epoxy
resins. Unreacted amine in the epoxy inhibits the peroxide catalyst
in the polyester causing an incomplete cure at the interface.
Sanding does not get rid of unreacted amine. The result is a poor
bond even though the surface appears cured. Debonding will be
the inevitable result."

Wonder if the vinyl sealer has polyester resins in it?

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Brian

You never know what you are capable of until you actually try.

https://www.howardguitarsdelaware.com/

A quick question for Todd; are you sealing with vinyl sealer or shellac?

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Jim Watts
http://jameswattsguitars.com

I've had problems with Z-poxy and System3, only under FP'd shellac, more pronounced on necks. No problem under Behlen's Rockhard.

Pat

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

Amine blush is not a problem related to any specific brand of epoxy. It is a problem acknowledged by all industries that use any formulation of amine cured epoxy and has been the focus of large sums of money spent on R&D to try and over come the issue. A lot of focus is now on prevention with some processes being undertaken in a sealed environment in which all air has been displaced by other gases whilst the epoxy is curing. This is a bit of a stretch for us but it does demonstrate how, where amine blush is concerned, prevention really is better than a cure.

As for thinner finish allowing amine bicarbonate to escape. I can't see how that would happen. We are not talking about some kind of spirit thinners here. The residue excretes from the epoxy yes, but once on the surface it is like oil and it seems happy to just sit there and screw up whatever you put on top of it, especially if that whatever undergoes a polymerisation process as it cures cause the blush has a way of reversing that process in a very ugly way. From the looks of Jim's photo, the blush appears to have caused an adhesion issue under the sealer which has allowed air to be pulled in under the finish. I would think over time, that those small pockets will grow and eventually flake off.

Nasty stuff but the answer is there, know the risk and take the proper measures to avoid them. Either that, or use something else which does not carry the risk. I guess that evolving as we have from using quite inert products that have all worked to some degree, but have also carried some negative element which makes them look second best to the new age ways of industrial chemistry, that it is quite easy for us to assume that the all new solution is complete.

The truth is however that most new solutions bring along their own set of problems...and when they are occurring at molecular level, the big draw back is that you can find yourself needing to learn more than you ever wanted to, not just to avoid them, but just to discover what they are. When all is said and done I guess we need to look at the old and the new and decide which product and process we are prepared to commit the time and effort to, that will tame the devil that is hiding behind the detail of our own inexperience.

Cheers

Kim

Thanks Todd.
This is turning into an interesting discussion.

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Jim Watts
http://jameswattsguitars.com