ammonium carbamate which in extreme cases appears as a visible white coating. Blushing is most prevalent when the temperature drops as after the curing process has started. Blushing if left on the surface willl effect subsequent coats of epoxy and paint and varnish if you try to coat over them without removing it. Specifically the varnish or paint will not set nor adhere to the substrate correctly. The best method for getting rid of the blush is to wet sand I find. This accomplishes two things in one, it both smoothes down the roughened surface thus preparing it for further coatings and washes off any blush at the same time, because you are sanding the surface you can tell which bits you have missed as the surface willl still be rough. You may think that sanding with an electric sander would be the way to go but I must caution you that dry sanding forces the wax deeper into the surface and clogs up the abrasive paper is short order. If you have a large area to sand and need to use a sander then you willl have to wash the surface down first in which case use plenty of clean water and some ammonia cleaner such as Comet to de wax the surface.
I should add as a final note that amine blush does not always happen especially if the ambient air temperature is warm, not too humid and stays at a stable level until the cure process in complete. Additionally some epoxies such as those sold by MAS do not blush and so they may be worth investigating before you go out and buy your next batch.
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