Epoxy Troubleshooting – amine blush.

Have you ever seen a waxy, often whitish haze form on your two pack epoxy coating?

Amine blush, as it is known, is a waxy substance that forms on the surface of some epoxies. In theory, being a soluble wax it can be removed by detergent washing, but it is not a condition you want to see.


Amine blush often appears as a whitish, waxy film on top of the coating surface. Image source - pcimag.com

So, what can happen if my floor shows amine blushing?

If your topcoat develops amine blush then you will obviously end up with visual defects and the surface will tend to pick up dirt more easily, so you will need to remove it if it occurs in your final coat. You cannot simply leave it there.

If you end up with amine blush in your basecoat, then you can expect crawling if you were to apply the second coat. You could also end up with large scale delamination as the amine blush essentially acts like a strong “mould release” across the affected surface.

Either way, it is a costly mistake that can be avoided by doing your homework on the resins and understanding why it happens (in the coaching classes I cover how to read data sheets and MSDS in order to understand the likelihood of amine blushing).

So, what causes amine blushing and how can I avoid it?…

Amine blushing is the result of the amine in the curing agent reacting with carbon dioxide and moisture to form the waxy substance. Some amines are more prone to the problem than others and fundamentally if your system is hydrophobic, or not miscible in water, then you have less risk of amine blushing.

A quick tech-talk side step, for those that are interested…in my experience, I have found isophorone diamine (IPD) based curing agents particularly susceptible to blushing and related surface defects. I mention IPD as it is a commonly used curing agent due to the fact it is highly reactive and cheap, so manufacturers tend to like it because they can use less of it. Being so reactive they tend to use a lot of diluent to boost the volume ratios, which further cheapens the product overall.

OK, so I mentioned that the amine blushing was a reaction with moisture and carbon dioxide. Therefore, a humid environment can be more prone to such problems, but it can also be quite inconsistent (happen one day and not the next) in hot, humid environments because the product crosslinks more quickly to begin with due to the higher ambient temperature.

The other extreme, is cold and wet conditions. In this case there is moisture in the air and the resin is slow curing giving the (blushing) reaction plenty of time to take place.

One scenario that many users do not consider is when they are looking to heat a room in order to speed up the curing process. They forget that a gas fired heater will be blowing carbon dioxide into the room, increasing the concentration of the gas compared to normal conditions and increasing the chance of amine blushing occurring (after all it is a reaction based on moisture and CO2).

So, how do I know if the resin is prone to blushing before I do a job?

Check the ideal curing conditions and product limitations supplied by the manufacturer. Pay particular attention to the humidity criteria and minimum temperatures stated on the data sheets. If in doubt, then simply ask the manufacturer.

Most applicators that have been doing floors for a while have seen some form of amine blushing. Have you seen the defect? What did you do?

Take care and talk to you later,


11 Responses to “Epoxy Troubleshooting – amine blush.”

  1. Mendy Malek says:

    Thanks for your explications.

    Mendy Malek

  2. Cinesh Mohan says:

    Thank you very much Jack

    Have you seen the defect? What did you do?

  3. Hello Cinesh,
    Sorry for the late reply… I am still trying to catch up after my business travels.
    To answer your question, yes I have seen amine blushing. It can vary in its form from a white haze to a waxy substance. The removal of it can be difficult. If it is a waxy substance, then it can be removed using detergents but if it is a film haze, then applicators would generally have to clean and then abrade the surface to remove the haze and then top coat again. Did that answer your question…..
    Thank you for your comment.
    Take care

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  8. RBM says:

    I have had an epoxy floor fail cohesively because of an amine blush. The coating was initially to be applied as an epoxy primer and then a 90 mil self leveling top coat. The coating out gassed terribly because the floor was planed and Shotblast prior to application. The concrete was very porous. A test area was applied utilizing epoxy block filler as an intermediate coat which cured the out gassing problem. The manufacture Okayed the block fill intermediate coat application. Directions giving by the manufacture in utilizing the block fill as an intermediate coating included a 12 hour recoat window with the sooner the better. The block filler was fast setting and so the top coat was installed anywhere from 4 to 16 hours. The failure of the coating started to occur within 30 days. The failure was occurring at the bond line between the block fill and top coat. An Amine blush was established as the cause. The coating had better adherence the closer you came to the shortest recoat window. The application was indoors with a floor temperature between 65 and 72F no facile burning equipment or heaters were running. CO2 air sampling was done without any high reading taken. The block filler is 100% solids epoxy resin polymer and polyamine curative. 80 percent of the floor was removed completely and polished. The remaining 20% started to fail later and needed to remain a coated floor so the top coat was removed to the block filled, sanded and solvent wiped. The same top coat was reinstalled and remains a solid well performing floor over a year later. It is of my opinion that the block filler realistically had no (0) recoat window and that the block filler should have been cleaned and abraded prior to the top coat and there wouldn’t have been an issue.
    What are your opinion and or experience with this type of problem? What do you think the manufacture should do or should have done knowing their product?
    Thanks RBM

  9. You certainly encountered some pain on that project.
    Firslty I am not familiar with using block fillers, let alone fast curing block fillers on flooring, so I probably can’t comment to much on the specifics.
    You may well be right about the block filler recoat window but you would have to rely a bit on the manufacturer’s advice and knowledge of the product specifics. You might rely a bit on your own gut feel if the block filler is specifically designed for other purposes. Meaning that you can chose not to accept the manufacturers first suggestion and seek another alternative suggestion (from the same manufacturer) that you are more comfortable with. For instance applying another sealer coat/s during the cooling cycle of the day to stop the pinholes.
    Cleaning off amine blushing can be difficult as the degree of blushing can vary from hazing to sticky waxy films. Meaning that sanding and solvent wiping may not have removed the blushing.
    It is hard for me to say what the manufacturer should or should not have done. Once there is a problem the focus should be on the solution and all parties should work together and aim to be fair and reasonable to all involved. Afterall what goes around comes around.
    I have noted, over the years, inconsistencies with certain types of curing agents. IPD is one of those curing agents that gave us difficulties when we were doing development work. The same batch would haze up on one section of the slab and not the other under similar environmental conditions. Temperature and humidty was not a problem, it was just inconsistent in behaviour…. and we coudl not track why.
    The use of IPD curing agents is widespread. It is cheap, highly reactive (so it can be heavily diluted), it is aliphatic (better for UV stability) and it is clear. So it would sound like the ideal curing agent but our experience forced us to use more expensive, less reactive curing agents and we are happy to do so as we simply don’t encounter the unpredictable behaviour of IPD.
    Take care

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