So you have applied the Epoxy coating as directed and it is showing a white bloom, is this going to cause you a problem? It is called an Amine Blush or bloom.

The bloom has been caused by ammonium bicarbonate salts during a change in humidity and temperature as the epoxy is curing.

After full cure, is the epoxy bloom hard and dry or is it stickier than the surrounding area of coating? Full cure will depend on the ambient temperature and time of year applied. See data sheet for full cure times at various temperatures.

If sticky still this stickiness could interfere with a top coats adhesion the main problems with a sticky amine bloom are as follows.

Risk of overcoating failure


Decreased stain resistance

Tendency to yellow

Softness of coating

Reduced chemical resistance.

If after full cure the bloom has hardened to the same hardness as the surrounding area then the problem is going to be aesthetic only, if the coating is slightly softer on cure or still sticky then it will have to be removed and applied again. See correction procedure below.

Amine is Alkaline so if you test the dried surface with a litmus paper you will be able to tell if the amine is still active.

Correction of the blush is possible.

Wash the surface with a detergent prior to re coating. Make sure that the detergent is thoroughly Rinsed from the surface. If you still have a sticky film. Gentle abrasion of the surface with a Scotchbrite nylex pad may be enough to remove it. If you do not intend to over paint the epoxy be careful not to damage the coating or you will have to repaint.

How do I ensure the bloom does not occur in the first place?

1 Paint on dry days, with low humidity.

2 Avoid painting on cold damp foggy winter evenings unless in a heated area.

3 Use the dew point calculator App from our web site.

Do not expose the component B to high levels of moisture or humidity. Ensure that the reaction time is as specified, usually leave for around ten minutes after mixing the A & B components. Use the exact mixture of component A to component B. Do not use more B than A in the mix. B is in most cases the hardener. It is the hardener you have to protect and be precise with its measurements. To every coating you apply as a good practice.

If you are on a maintenance project or facing a work shut down and have no choice over the conditions you have to paint in then contact our technical department and ask about our full range of MCU moisture curing urethanes that can be applied in all conditions cold and damp without any problems.

All the best



Do it right do it once

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