Official Luthiers Forum!

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

Snip.......Kim said




I don't use epoxy(although I have a few times years ago with no problems), but find this an interesting conversation. If the amines are some kind of "oily residue" is there a process that could be used to clean off this residue?

Todd's finished a bunch of guitars, using epoxy for pore filling, with no problems. As stated earlier Todd is methodical. Perhaps something in his finishing process cleans off the amines. (?????)

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I didn't mean to say it, but I meant what I said.
http://www.brackettinstruments.com/

Woody,

Your question appears to assume that amine blush is an unavoidable consequence of using epoxy and that is simply not the case. I have tried to be clear in my posts in stating that amine blush is strictly a consequence of epoxy being exposed to excessive moisture and carbon-dioxide that may be present in the air during mixing, application and curing of the product. It therefore stands to reason that the best way to avoid amine blush is to take steps to reduce exposure of the product to moisture and carbon-dioxide during those stages.

The point I had made in relation to Todd's suggestion he had never experienced an issue with amine blush in his many years of using epoxy was intended to reinforce the point that amine blush can be avoided. On that point I had not suggested Todd was "persnickety" in his process. Rather my comment was intended to point out that Todd has shown himself in the past to be quite methodical in his general approach to things and that of itself 'could' be the reason he has never had an issue with amine blush. I had also suggested that Todd's good fortune may well be a consequence of his location, i.e. a generally stable climate with low RH.

Once again I have no idea if either of these things explain why Todd has not had an issue because I have no real idea what Todd does or where Todd lives other than it is somewhere in the USA. But my message remains the same, amine blush 'can' be avoided 'if' you take the time to understand what it is, and why it is, and then take appropriate steps to minimise the risk. You can think what you like about how relevant amine blush is to the causation of those problems we have seen bought to light in this thread, but regardless of what your opinions are, they simply will not remove the fact that epoxy amine blush 'is' a common problem. It is problem acknowledged by science and by those industries which use epoxy on a regular basis, and it is a problem acknowledged by those who manufacture epoxy products. If anyone using epoxy products chooses to ignore that fact then chances are it could come back to bite them on the arse at some point when the only solution staring them in the face is the heartbreaking task of sanded off all their hard work back to bare wood, and to start over again. So to me it just seems good practice to know your enemy or go find some new friends to play with.

If anyone thinks this is all some kind of new voodoo, just Google: Epoxy Amine Blush

Its been around since they invented epoxy.

Cheers

Kim

Kim pretty much has it correct - I would only say that blush forms on the surface. It doesn't float up to the top through the coating. I should say for full disclosure that i am a tech advisor with West System epoxy. Other than that subtlety he's spot on.

We have our 207 hardener that is colorless and as blush free a formulation as is on the market, but it still is an amine based hardener and the potential for blush to form is still there. Anyone who claims their hardener is blush free and uses amines or polyamids is, I'll be generous, stretching the truth. Blush forms from the reaction of the amine reactive site exposed to the atmosphere and C02 in the air. It forms preferentially in the presence of moisture. So on days with high humidity it is more likely to form. The good news is it is easily removed with clear water. A wet paper towel wipe followed by a light sanding will prep the surface for finish coating.

I don't think the cloudiness shown in the picture is caused by blush. It would have been immediately apparent. I think it is more likely a result of moisture causing the cloudiness probably from sweat. Our 207 hardener is formulated to resist the clouding due to moisture. I believe the Mirror Coat System Three is also formulated to resist clouding and blush. Formulating with large, cyclic amine molecules can reduce blush formation to very nearly none in most ambient conditions. If you're working in a climate controlled environment - indoors with AC - blush is not likely to form with any hardener.

Thanks for tuning in on this Bruce and welcome to the OLF.



When I look at the image of Jim's guitar, I am seeing what looks to be a de-lamination issue rather than cloudiness. It looks much like small blisters directly over the filled pores and this is consistent with one of the many symptoms of amine blush. Perhaps Jim could tune back in a verify what he is seeing in the flesh. Maybe even give us all a closer look???

Cheers

Kim

I wanted to to bump this again and see if we can get Jim or others to elaborate on the problems. I have been using Devcon epoxy on fingerboards and my finisher and I have been using West System (with 207 hardener) for pore fill for at least 4 years with no problems. My finisher has been using West System for much longer. But if nothing else, I want to understand what I'm doing right so I keep doing it.

I also want to thank Bruce for chiming in. His response was prompted by an email I sent to their tech department. My first call to West System tech was about 27 years ago and they have always been great about answering questions.

I also got an email response from Mike at WestSystem and he had this to add:

1- Use paper towels with alcohol to clean the surface after sanding instead of a towel (any little speck of detergent could act as a mold release).
2- Heat the wood up slightly, then apply the epoxy as the wood is cooling down (this will draw epoxy in, rather than push air out).
3- Avoid applying epoxy when the humidity is really high.

Bruce, are you saying amine blush would not affect finish adhesion after such a long period of time? Any other explanation why we would see finish delamination along glue lines, especially delamination that recurs after refinishing?

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http://www.chassonguitars.com

This is why I had suggested that blush forms 'within' the curing epoxy and not 'just' on the surface. I had read (but cannot recall where now) that most of the residue does indeed form on the cured surface, however if during mixing the batch had absorbed enough Co2 and H2o to trigger the production of amine bicarbonate, then these migrate to the surface 'through' the mix. I have no science to prove this, but I suspect that some of these amine bicarbonate salts become suspended in the cured epoxy and what we see with the reoccurring ridge at the glue line of fretboards etc, is the result of them very gradually permeate to the surface through the cured epoxy. I say this because I have scraped just such a troublesome joint back to 'bare' wood just to be sure I got rid of any surface epoxy. I refinished and the problem came back the same as before...more than once, and the only epoxy was that which was freshly exposed through the scraping.

From what I understand, rinsing with fresh water as Bruce has suggested is a solution to remove the surface amine bicarbonate, but it does nothing to stop those within the mix from re-contaminating and I have heard of mixed results with using just plain water. For large surfaces like boat decks etc I guess a bit of amine bicarbonate residue being left behind is not going to be too detrimental to the over all look, but when dealing with fine woodwork finishing on relatively small decorative surfaces as we do, then 'any' imperfection sticks out like errrm. I certainly don't pretend to have the same expertise as Bruce, but the paper I linked to earlier appears to be based upon credible research based upon scientific principals and their findings indicate that successfully removing amine bicarbonate is a bit of a hit and miss affair and runs a poor second to taking appropriate measures to avoid causing it.. http://www.huntsman.com/performance_products/Media/Blushing_of_Amine-cured_Epoxy_Resins.pdf

My own experience certainly indicates that if indeed amine bicarbonates are what had cause the problem, then they remain active under the finish long after one would expect. I explained earlier how I watched as what had once been a beautiful Truoil finish over Indian Rosewood gradually broke down over time to becomes something quite horrible and I am not alone in that experience. We have had a number of threads on this forum where the same problem has happened to others using Truoil and in nearly every instance, epoxy had been used as a pore fill but amine blush can cause issues for many other finishes also.

It is difficult to provide images of what I am talking about because in an image, the finish just appears dull, like someone has spilt something on it and its been allowed to dry. But you can 'feel' what had happened and when you look closely (the best I have is a small plastic toy like hand held microscope @ 30x) you can see that directly over the filled pores, the Truoil has gathered and sunk back into the once filled pores and crystallised. This is also evident on the heel of the Queensland Maple neck where there is more endgrain. The shaft, apart from the fretboard glue line, is just fine. But then the pores are not that big in QLD Maple. I did not use epoxy on the spruce top and that still looks fine apart from play wear. Like wise the mulga headstock overlay, its a very fine grain wood with tiny pores, no epoxy, no problem. But the EIR and endgrain of the neck did react. It is worth mentioning that 'all' surfaces were finished at the same time with complete burnish session over the entire guitar building the finish like a french polish.

As explained earlier for a while the whole guitar looked great, but then a few localised dull patches began to appear. I tried buffing them but this made matters worse and I discovered the reason was that these patches had in fact softened a little. Never actually sticky to touch, but softer than those areas around them that were yet unaffected. Gradually these dull patches began to spread so I decided to give up trying to fix things and just watch what happens over time. After a year or so around 50% of the back or more had become affected. It seems as if the oil softens just enough to 'slowly' migrate toward the nearest epoxy filled pore. Once there the oil seems to interact with the epoxy causing it to soften as well. In my little microscope it looks like the Truoil and epoxy eventually combine over many months and then dry out completely to form what looks like clear, dark, toffee crystals. You can even see evidence of minute bubbles in the crystals and what looks like minute craters where other bubbles have been ruptured. The feel by this time is somewhat like sand paper. Now a couple of years on, this reaction seems to have stopped but one thing is clear the deeper the pores, the worse that area had reacted and the glue line at the FB, well that is still a work in progress because the line may be thin, but it is deep in epoxy and short of pulling the board, I don't see that sorting itself out for a very long time.

I may fool with some lighting and macro tomorrow to see if I can provide some images. I have no conclusive proof that amine blush was the issue here, but boy there is a lot pointing in that direction and epoxy is the one common denominator with just about every similar finish breakdown issue I have seen.

Cheers

Kim

Todd, I always go "no tie coats". Tie coats are much too dangerous in the shop. Like long hair they can get caught in machinery.
I know you are a natty dresser but dude, no ties in the shop, OK ?

L.

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Cut to size.....Beat to fit.....Paint to match.

Just say no...

Here is a picture of a 3 year old guitar that I luckily kept. Here is the process,, Zpoxy fill, sand back to wood, 50/50 zpoxy/da wash coat, sand with 320, shellac seal coat, light scuff, nitro finish. I did not use water to clean after sanding zpoxy coats, just a tack cloth. Humidity level was in the 40% to 45% range. Not sure about CO2 levels, but was done indoors, in my shop without a fan running. I quit using zpoxy before this ever occured (took at least a year before it started), since I didn't care for the fact that it had to be forced into the pores... I was concerned that the zpoxy may bridge over some of the pores.

The finish right now has a rough texture. I haven't decided whether to try to refinish or just replace the neck. Sorry about the picture quality, but it is very difficult to get it to show up in a picture.

Thanks, Chuck

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I get that amines are common to all epoxy but this sure seems like a lot of Zpoxy users.

And it still doesn't explain why so many people only have problems on necks.

And it looks like it's localized around pores. Is it possible that the epoxy is delaminating from the wood at the pores and not the finish from the epoxy?

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http://www.chassonguitars.com

Chuck, do you know how long the zpoxy cured before coating with lacquer?

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Formerly known as Adaboy.......

Chuck's post got me thinking...is it possible, if the epoxy does bridge some of the pores, that the blush is forming on the underside surface of the epoxy...i.e., between the epoxy and mahogany? Perhaps a reaction between the amines and the wood, or moisture trapped in the wood prior to application?

Alright, so looking at it under a magnifying glass it appears that the finish discolors to grayish tint first and them some time later the finish will bubble right over the discoloration. I'm guessing that whatever reaction is occuring produces a gas or moisture by product and over time the build up of pressure locally delams the finish creating a little bubble.
Thanks for all the good information you've posted on blushing Kim and to the west systems folks for checking in too.
This seems to be more common than I ever imagined.

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Jim Watts
http://jameswattsguitars.com

Darryl Young
Post subject: Re: epoxy filler caution

Chuck, do you know how long the zpoxy cured before coating with lacquer?



Minimum of 3 days, maybe 5. Been too long to remember for sure.

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