Have you noticed a blotchy, sometimes glossy appearance with tan or brownish casts? This is surfactant leaching – a concentration of water-soluble ingredients on water-based paint, that’s more likely with tinted paints than with white or factory-coloured paints.
Causes of surfactant leaching include:
- Painting in cool, humid conditions.
- Exposure of mist, dew or other moisture sources during the initial paint curing stages.
If the problem occurs in the first day after painting, the water-soluble material can sometimes be rinsed off easily. Fortunately, even more stubborn cases will generally wear off in a month or so. Generally, the leached surfactant does not lessen the durability of the paint film, it just looks unsightly. On exterior surfaces, surfactant leaching will usually weather off over a short period (approximately a month) without the need for intervention, rinsing with fresh water can help to wash it away.
Under severe conditions, surfactant leaching may reappear once or twice until all the surfactant has been removed. The effect will be less noticeable each time and can be removed by washing in the same manner as prescribed above. On rare occasions, the leached material may stain the paint surface. This would require a repaint once the surface has been thoroughly washed and the paint film has cured.
Avoid painting in the late afternoon if cool, damp conditions are expected in the evening or overnight.
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