Proper Preparation Prevents Painting Problems

A fresh coat of paint is a basic ingredient in getting a home ready to sell and increasing its curb appeal. But sometimes this seemingly quick fix hits a snag.

Usually it’s the paint itself that gets the blame but, in most cases, the cause lies elsewhere. Here are some common problems and ways to prevent them:

Blistering is the earliest stage of peeling and is usually caused by moisture trapped under the new paint coat or by poor surface preparation. If it occurs within the first few weeks, it’s probably caused by trapped moisture.

Though latex paint can usually be applied to damp surfaces without any problem, alkyd and other oil-based paints form a moisture-barrier skin that traps the water inside. The water then turns to vapor and forms blisters. To avoid this, never paint with alkyds when dew is on the siding or too soon after you’ve washed the old surface. Also, never paint when the temperature is higher than 90 degrees.

If blisters appear after a month or so, the problem is probably poor surface preparation. If you washed the surface with detergents, did you take the time to rinse completely? Unless this type of film is removed before painting, it can cause blistering. Also, glossy surfaces must be given a light sanding so the new paint will grip well.

Peeling is the curling of large pieces of dried paint and is merely a later manifestation of blistering. Severe peeling might also indicate use of a poor primer or a heavy film of dirt, grease or dust. Prevention involves sanding or wiping the old finish with a deglossing liquid, then following the manufacturer’s directions about what primer to use before applying the top coat of paint.

Alligatoring is a cracking and flaking of the paint in a square pattern. It can result from applying paint over a previous coat that had a high-gloss finish that was not sanded, use of the wrong primer or use of old paint.

To repair the condition, sand the surface smooth and apply the proper primer before applying a new top coat.

Checking is a series of long lines, with shorter check marks crossing between, usually caused by the wood’s expanding and contracting. This can be a problem with exposed plywood siding regardless of the kind of paint used. Sanding and then applying a new coat of wood primer will usually solve the problem. But if the new paint shows signs of coming loose, complete removal of the old paint is required.

Wrinkling results in a crinkled surface that is caused by interfering with required drying time. Contributing factors are too-thick finish coat, building up of too many layers, undercoat that was not completely dry, wrong solvent or improperly stirred paint. Repair by sanding smooth and applying proper primer before painting top coat.

Chalking or powdering characteristics are designed into some paints to keep the surface looking new. Chalking of old paint can interfere with proper bonding of a new coat, so scrub off as much as possible beforehand. In severe cases you might have to apply a bonding primer or sealer.

Mildew manifests itself as patches of black spots. Though most exterior paints contain mildew-inhibiting ingredients, none works under all circumstances. Remove mildew by washing the affected area with a bleach solution. Use one-third cup powdered laundry detergent, two-thirds cup household cleaner containing trisodium phosphate and one quart household bleach. Wear long pants, a long-sleeved shirt, gloves, goggles and a respirator to avoid breathing the fumes.

Stains that bleed through the paint often are the result of sap from knots in the wood seeping through the surface. But they also can be caused by rust from nails and hardware. Many discolorations bleed through coat after coat of paint, so simply repainting is not the answer. Instead, apply a primary coat of stain-killer, such as pigmented shellac-base sealer, then apply your paint.