Even knowledgeable do-it-yourselfers and professional painters occasionally run into problems with their interior paint jobs. Some of these problems are immediately apparent; others develop over time. This chart shows some of the more common interior paint problems. It offers suggestions on the possible causes of these troubles, and advice on how to correct them. When correcting any paint problem, it is important to remember that top quality paints and coatings offer far better protection and performance than lower quality coatings. For that reason, they are generally the most cost-effective choice for doing any type of repainting.

BLOCKING: The undesirable sticking together of two painted surfaces, such as a door sticking to the jamb, or a window sticking to its frame.

Possible Factors:
• putting a door, window, or other item into service before the freshly applied paint is adequately dry
•use of a lower quality paint
•use of semi-gloss or gloss paint, which may tend to block more than flat paints or those with eggshell or satin sheen
•use of a highly tinted paint, which is more likely to stick than a light-colored paint
• use of an exterior latex paint for an indoor application

Solution: Applying talcum powder to both surfaces can be an immediate way to reduce blocking. If repainting, consider using paint with a lower sheen, e.g., a flat or satin finish, rather than a semi-gloss or gloss; if possible, switch to a lighter-colored paint. Most important, be sure to allow adequate drying time when applying fresh paint.

STAIN BLEED-THROUGH: Discoloration of the paint due to migration of stains from the surface painted, or from the substrate underneath.

Possible Factors:
• painting over dirt, water stains, rust, etc., without proper surface preparation (cleaning/rinsing, application of stain-blocking primer)
• use of the wrong type of primer, i.e., one that is not sufficiently stain-resistant
• moisture coming from behind the wall or trim, and transporting stains to the surface

Solution: Eliminate any sources of excess moisture behind the wall or trim. Clean the surface and remove as much of the discoloration as possible. Apply one or two coats of a stain-blocking primer (a second coat enhances stain-blocking). On very severe stains, an oil-based or alcohol-based primer will work best.

MILDEW: Black, gray or brown spots or splotches on the surface of the paint.

Solution: Treat the mildew with a 3:1 mixture of water and household bleach. Sponge the bleach mixture onto the mildew, allow it to remain on the surface for at least 20 minutes, and reapply as it dries. (Always wear goggles, rubber gloves and old clothes when working with bleach.) Rinse the area thoroughly with water, then wash it with a mild detergent, and rinse again. To protect against mildew, use a top quality latex paint, and clean when necessary with bleach/ detergent solution. Consider installing an exhaust fan in high moisture areas. NOTE: Never combine bleach and ammonia, as this will release poisonous gas.

POOR HIDING: Failure of dry paint to obscure or "hide" the surface to which it is applied.

Possible Factors:
• use of a low quality paint
• application of the paint with a low quality brush or roller; or use of too short a roller nap
• application of a paint that is much lighter in color than the surface below
• use of a paint with low-hiding organic pigments (e.g., yellow)
• application of paint at a higher spread rate than recommended
• painting a surface that is very smooth or slick

Solution: When painting over a dark color or pattern, or when applying a low-hiding, organic-colored paint like yellow, prime the surface before painting. If possible, have the primer tinted toward the color of the paint, following the primer manufacturer's recommendations. Use a top quality paint for best hiding.* Apply the paint with quality rollers or brushes, and be sure to use the recommended roller nap. Follow the manufacturer's recommendations on spread rate.

*Some low quality flat paints have good "dry hiding," but their hiding will suffer if they become wet from water, cooking oil, etc.

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