Paint Blistering are bubbles that can occur underneath existing paint. This can can leave your home looking drabber than ever. Paint blistering can happen in two levels; the first is when the top layer has lost adhesion only with the layer beneath it and the second is when all layers have lost adhesion with the substrate.
Paint Blistering Causes:
Aged paint combined with heat exposure is a common cause of blistering on a substrate. Paint becomes brittle over years of enduring environmental changes. As temperature increases and decreases, the substrate expands and contracts. However, brittle paint has no flexibility to expand and contract with the substrate and therefore, hairline cracks appear in the paint film. Once these cracks are intact, moisture entrapment is ensured through weather conditions, thus, the paint’s adhesion with the substrate is weakened and blistering occurs.
Moisture entrapment can occur when moisture from the atmosphere is present in the substrate prior to painting. While this moisture rises to the surface due to the sun urging it to evaporate, blistering can occur again. Moreover, if you initially painted on a substrate without cleaning before painting or that was contaminated with mould, dust, or salt, you will also experience blistering due to lack of adhesion with the substrate.
How to fix paint blistering:
Remove blisters individually and then paint over it.
Similar to a virus, once one blister occurs there is sure to be further blistering. If you remove all of the blisters individually and cover it up with paint, there is no guarantee that they won’t come back.While this is an option, may be ineffective.
Remove all layers of paint.
In this situation you would completely remove all paint layers until bare.
Ways to avoid paint blistering:
Clean the substrate
Painters must clean the surfaces of the substrate so that the particles in the paint can bind with the substrate directly instead of the layer of dust covering the substrate. This phase is key to ensuring adhesion.
Choose the right colour
Lighter colours tend to not absorb heat as much as darker colours. This means less expansion of the substrate and less likelihood of blistering.
Make sure the substrate is dry.
Moisture from contamination, weather conditions and moisture left from the preparation phase of painting is going to cause blistering. You can purchase a moisture meter from your local hardware store and will quickly determine the moisture level of your substrate. To avoid blistering, moisture levels must remain low (below 15%).