Solvent-Based Top Coat Problems

Blistering

• Blistering is a pattern of bubbles that appears on topcoat surfaces. Blistering occurs when moisture within the wood pushes its way to the surface and breaks the adhesive bond of paint. The problem may have started when solvent-based top coats were applied over wood with high moisture contents. It can be repaired by scraping off the affected area, sanding the surface to smoothness, priming and painting.

Cracking

• Hairline cracks can appear in the paint at random places across the surface during the early stages. Left unchecked, they will grow in number to form a series of deeper cracks that will lead to paint flaking off the wall. This coatings failure is most commonly caused by applying an alkyd coating over multiple layers of old paint without properly preparing the surface. If the problem is widespread, the best remedy is to scrape off all the loose paint layers, prime and then paint.

Alligatoring

• When you apply a solvent-based top coat over a primer that has not thoroughly dried, the top coat can develop a lattice of horizontal and vertical cracks that resembles an alligator's back. The only solution is to scrape off the paint and primer in the affected areas, sand the surface until it becomes smooth, and then prime the surface. It's important to give the primer adequate time to dry before applying the top coat.

Chalking

• Over time, some grades of solvent-based paint will break down to release powdery grit on surfaces. This will alter a paint's sheen and may also contribute to some noticeable color-fading, especially with deeper-colored paints. Although chalking commonly occurs with paints as they age, the problem happens much more quickly with lower grades of alkyd paints. While unattractive, the chalking does not represent a complete coatings failure. Chalking can be removed by rinsing down the wall with a pressure washer. This is a necessary step before applying another coat of paint.

Peeling

• Peeling occurs when large chunks of paint separate, curl up, and pull away from the wall. This can happen when a solvent-based paint has been applied too thinly, especially when applied without priming or when the moisture content of wood siding is excessive. In some cases, peeling occurs after the paint had already begun blistering. If the problem is widespread, the best solution may be to scrape off all the paint, apply a peel-stopping primer, and switch to a 100 percent acrylic latex topcoat.