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Kind of ironic that the cure for amine blush is to wash off with water which is what the users are trying to avoid by using epoxy in the first place.
As Kim said you can't sand it off it will only drive it into the wood. You need to wash off with water first.
L.

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

Yes it is kind of ironic Link, I guess the real answer is to be aware of amine blush and what causes it.

It seems many who use epoxy have not heard of amine blush, or if they have, assume it is not something they need concern themselves with as it has never happened in their shop to this point despite using epoxy for years.....To think that way is a gamble IMO. Whilst most of us 'have' used epoxy successfully for years without issue, it is fair to say that use was primarily as an adhesive. Amine blush does not affect bond strength so it is also fair to say that even if you had encountered amine blush in the past, you probably did not notice because in that situation it is not a problem.

On the other hand it is only quite recently that many of us have started to use epoxy products as a fill, in that application, amine blush can be a very big problem. When post are made on this forum and others about finish problems, it is interesting to read some of the suggestions put forward as to what the cause may be. Everything from old product, bad batch, wrong method etc, etc..all come up each time, and indeed the issues could be one, or a combination of those things, but despite the growing use of epoxy 'under' the finish within this craft, it is very rare to see anyone mention epoxy amine blush as a possible cause. But more and more, as I read about fuzziness developing on Truoil after a few month curing, french polish going dull and sticky, glue lines raising under the finish that just keep lifting no matter how many times you sand flat and re-polish etc, etc, I can't help but think we are going to see a lot more of this sort of stuff until folks acknowledge amine blush and take steps to eliminate it from the equation.

What I am saying here is that fore warned is fore armed and if one understands amine blush they can begin to remove or reduce those elements which are responsible for causing it from the working environment. I truly wish I had heard of amine blush myself 'prior' to developing my now infamous skin reaction to epoxy, for it was not understanding which had caused me to repeatedly expose myself to epoxy as I sanded and reapplied zpoxy in an effort to remove fisheye that was forming in the wet epoxy that I now know was caused by amine blush. At the time I was thinking the fisheye was caused by some sort of contamination like silicone in the rosewood. I had asked advice but it seemed noone had heard of amine blush. So with the assumption being it was a silicone contamination, it was suggested I wash the surface with thinners, something that would 'bite' into the surface of the epoxy, and then sand, wash again and repeat the process until the fisheye was gone.....the rest is history, as is my bodies tolerance to the irritants within epoxy.

Anyhow that point made, the saving grace should you be pore filling with epoxy and find your project has developed amine blush, is that epoxy does a great job of sealing the wood from moisture. So you can wash and scour to your hearts content to remove the amine blush BEFORE you sand back ...not much help on a fretboard though but if you take the proper precautions, amine blush does not need to become an issue in any application.

Cheers

Kim

This has been a very useful thread. A big thanks to Mark and Kim especially for their information. Finishing remains the hardest part of this process to get right.

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

Kim,
Can you help to reiterate some precautions? Thus far, I've learned that practically speaking, the reaction forming amine blush can be stopped or slowed by

1) Dry environment
2) Low CO2 levels -- ie

I was wondering if amine blush does form, do you try and clean up with water or can you use something like denatured alcohol?

Many Thanks

Good information here, thanks to all who have posted. One more thing to worry about, blush.

I've used this glue for some time with no problems, mainly fingerboard joints. Part A, for
me at least, I have to heat if before use, makes life much easier. HHG pot or a little
heat from my heat gun and I'm ready to go. It's never let me down so I'll stick with it.
Blush and all, mask wearing is a must.

_________________
Bruce Herrmann
"What lies behind us and what lies before us are tiny matters compared to what lies within us."

Amine Blush is salts of Amine Carbonate, formed by amines reacting with water and CO2 during the cure

Best way to remove is to create Hydrates of Amine Carbonate <- wash with warm soapy water.

Steps to Minimize formation of Amine Blush:

use the right epoxy. Epoxies that use a very basic amine cure tend to blush much worse than those that utilize cyclic amines.
Work in low humidity (not really compatable with our desired 45% RH working environment)
Minimize CO2 during mix (Kim lists some steps you can take)
work at higher temperature
de-blush before applying fresh epoxy over cured epoxy.

note that epoxies that utilize cyclic amines not only blush less, they also tend to have lower modulus (i.e. less desirable for guitar building)

The best hint is to not use epoxy unless you have to... Are you building waterproof guitars ?

BTW I also have epoxy sensitivity issues due to a past in composite aircraft construction

-jd

As JD has indicated in his post Simon, the best way to remove amine blush should it occur is with warm water to which a mild soap (dish washing liquid) has been added. Your aim would be to dissolve/dilute the salts and a nylon scouring pad should be used to abrade the surface during application of the soapy water. Once rinsed and dried, you would then sand the epoxy back as normal.

JD also mentioned those epoxy products that are produced to be less prone to blush also have a lower MOE. This makes them ideal for situations where resistance to abrasion is a desirable thing, but I cannot see where the properties of flexible resilience would be a benefit in this craft, so we are stuck with the more crude variants of epoxy which cure to a more crystalline state making them easy to sand. Unfortunately it is also these 'less refine' products that are most likely to cause a sensitivity issues for the user.

As for doing what you can to avoid epoxy amine blush. Well yes, 'dry' is good and so too is preventing the build up of CO2. If you work epoxy in an area with less than ideal air circulation, then you cannot hope to avoid a build up of CO2 and moisture because your own respiration will be providing more than enough of both in problematic concentrations. Worse still would be the problematic concentration of epoxy fumes that will be in the air the user is breathing...do not kid yourself into believing that it is only the epoxy that comes in direct contact with the skin that can cause an issue. The molecular structure of the fumes are such that they will quite freely penetrate right through your skin, its pretty insidious stuff where dealing with here.

That said, I think it is important not to freak out and reject this useful tool altogether. Epoxy can be used safely and the cool thing is that in taking the single most important step in making the product safer to use by providing really good ventilation, you are also taking the most important step in avoiding amine blush. So I will say it again, if you can wait for low RH before using epoxy, then do so. If you can work outside when using epoxy, do so. If you can't work outside when using epoxy, keep a fan running at all times so that fresh oxygen rich air is moving over you and the project, pushing your moisture and CO2 laden breath away from the project, and more importantly, pushing the toxic epoxy fumes away from any exposed skin.

Cheers

Kim

I would also strongly recommend wearing a respirator with a carbon cartridge when working with epoxy as the fumes can also enter your bloodstream via your lungs... In my case, all I have to do is is walk into a composites shop where epoxy is curing and I break out with rashes on both forearms.

-jd