Paint Failure: Alligatoring: Notes From Vancouver’s Best Painters

Vancouver’s Best Painters:  Call: 604-PAINTER

Improper application and thickness control of the paint film can lead to coating failures. These are definitely within the control of the painter.

Moisture can also cause coating failures. These failures can occur as a result of:

•           Painting over wet or moisture-contaminated surfaces

•           Rain falling or moisture condensing on wet or insufficiently dried paint

•           Moisture seeping into a building or structure as result of improper construction Many paint problems, particularly with exterior wood, are caused by moisture, It is important to eliminate sources of moisture and ensure that a substrate is dry before painting. This subject is discussed in more detail later in this module.

TYPES OF EXTERIOR FAILURES

Many types of coating failures have characteristic appearances and specific causes, which are described in this module. The following paragraphs discuss the causes and remedies for most of the coating failures you will encounter.

ALLIGATORING

Alligatoring is seen as pronounced wide cracks over an entire surface. These cracks may not reach the substrate; they may affect a single layer of coating film only. Alligatoring may begin as checking or cracking, but the breaks tend to grow wider at the bottom as wel’ as the top. The topcoating contracts, exposing portions of the undercoat. In an extreme case of alligatoring, the islands of coating between interlacing breaks have not only contracted in area, but have increased in thickness. Consequently, they become wrinkled.

Alligatoring is often caused by failure of the topcoat to bond smoothly to a glossy coat beneath it. A glossy finish is too hard to provide a good bond. In addition, application of an extremely hard coating over a soft primer can result in alligatoring. Alligatoring also may be caused by not allowing time for the undercoat to dry before recoating.

Another possible cause is the natural aging of oil-based paints in extreme climates of freezing and thawing. Also, the moisture absorption/drying-out process, combined with everyday expansion and contraction, results in a loss of paint film elasticity.

Other possible causes include application of a shorter oil-type finish over a longer oil-type undercoat or primer. This problem is magnified if the finish is applied before the undercoat is completely cured. Another cause is a coating that is too thick.

Rick Anderson

www.vancouversbestpainters.com painters painting in the Vancouver area call toll free:

1-800-PRO-PAINTER or visit www.vancouverindustrialpainting.com or call locally:

604-PAINTER