Amine blush can appear as a wax-like film on cured epoxy surfaces. This can clog sandpaper or inhibit subsequent bonding, but it can easily be removed.
To reduce blushing is to work in warm temperatures and avoid conditions where moisture is coming out of the air as temperatures fall.
How to remove
Wash the surface with clean water (not solvent) and an abrasive pad, such as Scotch-Brite(TM) 7447 General Purpose Hand Pads. Dry the surface with paper towels to remove the dissolved blush before it dries on the surface. Sand any remaining glossy areas with 80-grit sandpaper. Wet-sanding will also remove the amine blush. If a release fabric is applied over the surface of fresh epoxy, amine blush will be removed when the release fabric is peeled from the cured epoxy, and no additional sanding is required.
** Please note: Aggressive solvents like Acetone will not remove the blush.
Epoxy surfaces that have not fully cured may be bonded to or coated with epoxy without washing or sanding. Before applying coatings other than epoxy (paints, bottom paints, varnishes, gelcoats, etc.), allow epoxy surfaces to cure fully, then wash and sand.
Hardwoods-Sand with 80-grit paper.
Teak/oily woods- Wipe with acetone 15 minutes before coating allowing the product to penetrate correctly. Make sure that the solvent has completely evaporated and dried before you start your job.
Porous woods-No special preparation needed. Remove dust.
Steel, lead-Remove contamination, sand or grind to bright metal, coat with epoxy then sand fresh epoxy into a surface — re-coat or bond after first coat gels.
Aluminum-Sand and prepare with 860 Aluminum Etch Kit.
Polyester (fiberglass)-Clean contamination with a silicone and wax remover such as DuPont Prep-Sol(TM) 3919S. Sand with 80-grit paper to a dull finish.
Plastic-Adhesion varies. If plastic is impenetrable to solvents such as acetone, epoxy generally will not bond to it.
( Please Note - material such as polyethylene, polypropylene, nylon, and polycarbonate usually will not bond)
Hard, rigid plastics such as PVC, ABS, and styrene provide better adhesion with proper surface preparation. After sanding, flame oxidizing (by quickly passing propane torch over the surface without melting the plastic) can improve bonding in some plastics. It's a good idea to test on a plastic that you are unsure.