BLISTERING

Bubbles resulting from localized loss of adhesion and lifting of the paint film from urderlying surface wet surface. 

POSSIBLE CAUSES:
Applying oil-based or alkyd paint over a damp or wet surface. 
Moisture seeping into the home through the exterior walls (less likely with acrylic paint). 
Exposure of acrylic paint film to high humidity or moisture shortly after paint has dried, especially if there was inadequate surface preparation.

SOLUTION:
If blisters do not go all the way down to the substrate: Remove blisters by scraping, and sanding, and repaint with a quality acrylic interior paint. If blisters go down to the substrate: Remove the source of moisture, if possible. Repair loose sealant; consider installing vents or exhaust fans. Remove blisters as above, remembering to prime before applying the top coat.

BLOCKING

Undesirable sticking together of two painted surfaces when pressed together (e.g., a door sticking to the jamb).

POSSIBLE CAUSES:
Not allowing sufficient dry time for the coating before closing doors or windows. Use of low quality semigloss or gloss paints.

SOLUTION:
Use top quality semigloss or gloss acrylic paint. Low quality paints can have poor block resistance, especially in warm, damp conditions. Follow paint label instructions regarding dry times. Acrylic paints generally have better early block resistance then vinyl acrylic paints or alkyd or oil-based paints; however, alkyds develop superior block resistance over time. Application of talcum powder can relieve persistent blocking.

BURNISHING

Increase in gloss or sheen of paint film when subjected to rubbing, scrubbing or having an object brush up against it.

POSSIBLE CAUSES:
Use of flat paint in highly trafficked areas, where a higher sheen level would be desirable. Frequent washing and spot cleaning. Objects (furniture, for example) rubbing against the walls. Use of lower grades of paint with poor stain and scrub resistance (see Poor Stain Resistance and Poor Scrub Resistance).


SOLUTION:
Paint heavy wear areas that require regular cleaning (e.g., doors, window sills and trim) with a top quality acrylic paint, because this type of paint offers both durability and easier cleaning capability. In high traffic areas, choose a semigloss or gloss rather than a flat sheen level. Clean painted surfaces with a soft cloth or sponge and non-abrasive cleansers; rinse with clean water.

CRACKING / FLAKING

The splitting of a dry paint film through at least one coat as a result of aging, which ultimately will lead to complete failure of the paint. In its early stages, the problem appears as hairline cracks; in its later stages, flaking occurs.

POSSIBLE CAUSES:
Use of lower quality paint that has inadequate adhesion and flexibility.Overthinning or overspreading the paint. Inadequate surface preparation, or applying the paint to bare wood without first applying a primer.  Excessive hardening and embrittlement of alkyd paint as the paint job ages.

SOLUTION:
Removing loose and flaking paint with a scraper or wire brush, sanding the surface and feathering the edges. If the flaking occurs in multiple layers of paint, use of a filler may be necessary. Prime bare wood areas before repainting. Use of a top quality primer and top coat should prevent a recurrence of the problem.

FOAMING / CRATERING

Formation of bubbles (foaming) and resulting small, round concave depressions (cratering) when bubbles break in a paint film, during paint application and drying.

POSSIBLE CAUSES:
Shaking a partially filled can of paint. Use of low quality paint or very old acrylic paints. Applying (especially rolling) paint too rapidly. Use of a roller cover with wrong nap length. Excessive rolling or brushing of the paint. Applying a gloss or semigloss paint over a porous surface.

SOLUTION:
All paints will foam to some degree during application; however, higher quality paints are formulated so the bubbles break while the paint is still wet, allowing for good flow and appearance. Avoid excessive rolling or brushing of the paint or using paint that is more than a year old. Apply gloss and semigloss paints with a short nap roller, and apply an appropriate sealer or primer before using such paint over a porous surface. Problem areas should be sanded before repainting.

MILDEW

Black, grey or brown spots or areas on the surface of paint or sealant.

POSSIBLE CAUSES:
Forms most often on areas that tend to be damp, or receive little or no direct sunlight (e.g., bathrooms, kitchens and laundry rooms). Use of an alkyd or oil-based paint, or lower quality acrylic paint. Failure to prime bare wood surface before applying the paint. Painting over a substrate or coating on which mildew has not been removed.

SOLUTION:
Test for mildew by applying a few drops of household bleach to the area; if it is bleached away, the discolourant is probably mildew. Remove all mildew from the surface by scrubbing with a diluted household bleach solution (one part bleach, three parts water), while wearing rubber gloves and eye protection. Rinse thoroughly. To protect against mildew, use a top quality acrylic paint, and clean when necessary with bleach/detergent solution. Consider installing an exhaust fan in high moisture areas.

MUD CRACKING

Deep, irregular cracks resembling dried mud in dry paint film.

POSSIBLE CAUSES:
Paint applied too thickly, usually over a porous surface. Paint applied too thickly, to improve inherent poor hiding (coverage) of a lower quality paint. Paint is allowed to build up in corners upon application.

SOLUTION:
Remove coating by scraping and sanding. Prime and repaint, using a top quality acrylic paint. Mud-cracked areas can also be repaired by sanding the surface smooth before repainting with a top quality acrylic paint. This type of paint is likely to prevent recurrence of mud cracking, because it is relatively more flexible than alkyd paint, oil-based paint and ordinary acrylic paint. Quality paints have a higher solids content, which reduces the tendency to mud crack. They also have very good application and hiding properties, which minimise the tendency to apply too thick a coat of paint.

PICTURE FRAMING

An effect of non uniform colour that can appear when a wall is painted with a roller, but is brushed at the corners. The brushed areas generally appear darker, resembling the "frame" of a "picture." Also, sprayed areas may be darker than neighbouring sections that are brushed or rolled. Picture framing can also refer to sheen effects.

POSSIBLE CAUSES:
Usually a hiding (coverage) effect. Brushing will generally result in lower spread rates than rolling, producing a thicker film and more hiding. Adding colourant to a non tintable paint or using the wrong type or level of colourant, resulting in variation in colour, depending on method of application.

SOLUTION:
Make sure that spread rates with brushes and rollers are similar. Don't cut in the entire room before roller coating. Work in smaller sections of the room to maintain a "wet edge." With tinted paints, be sure the correct colourant-base combinations are used. Factory colours, as well as in-store tints, should be thoroughly shaken at time of sale.

POOR FLOW / LEVELING

Failure of paint to dry to a smooth film, resulting in unsightly brush and roller marks after the paint dries.

POSSIBLE CAUSES:
Use of lower quality paint Application of additional paint to "touch up" partially dried painted areas. Re-brushing or re-rolling partially dried painted areas. Use of the wrong type of roller cover or poor quality brush.

SOLUTION:
Use top quality acrylic paints, which are generally formulated with ingredients that enhance paint flow. Brush and roller marks thus tend to "flow out" and form a smooth film. When using a roller, be sure to use a cover with the recommended nap length for the type of paint being used. Use of a high quality brush is important; a poor brush can result in bad flow and leveling with any paint.

POOR HIDING

Failure of dried paint to obscure or "hide" the surface to which it is applied.

POSSIBLE CAUSES:
Use of low quality paint. Use of low quality tools/wrong roller cover. Use of an improper combination of tinting base and tinting colour.
Poor flow and leveling (see Poor Flow/Leveling).
Use of a paint that is much lighter in colour than the substrate, or that primarily contains low-hiding organic pigments. Application of paint at a higher spread rate than recommended.

SOLUTION:
If the substrate is significantly darker or is a patterned wallpaper, it should be primed before applying a top coat. Use a top quality paint for better hiding and flow. Use quality tools; use the recommended roller nap, if rolling. Follow manufacturer's recommendation on spread rate; if using tinted paint, use the correct tinting base. Where a low-hiding organic colour must be used, apply a primer first.

POOR SCRUB RESISTANCE

Wearing away or removal of the paint film when scrubbed with a brush, sponge, or cloth.

POSSIBLE CAUSES:
Choosing the wrong sheen for the area. Use of a lower quality paint. Use of an overly aggressive scrub medium (see Burnishing). Inadequate dry time allowed after application of the paint before washing it.

SOLUTION:
Areas that need frequent cleaning require a high quality paint formulated to provide such performance. High traffic areas may require a semigloss or gloss paint rather than a flat paint to provide good scrub resistance. Allow adequate dry time, as scrub resistance will not fully develop until the paint is thoroughly cured. Typically, this will be one week. Try washing the painted surface with the least abrasive material and mildest detergent first.

POOR SHEEN UNIFORMITY

Shiny spots or dull spots (also known as "flashing") on a painted surface; uneven gloss.

POSSIBLE CAUSES:
Uneven spread rate. Failure to properly prime a porous surface, or surface with varying degrees of porosity. Poor application resulting in lapping (see Lapping).

SOLUTION:
New substrates should be primed/sealed before applying the top coat to ensure a uniformly porous surface. Without the use of a primer or sealer, a second coat of paint will more likely be needed. Make sure to apply paint from "wet to dry" to prevent lapping. Often, applying an additional coat will even out sheen irregularities.

POOR STAIN RESISTANCE

Failure of the paint to resist absorption of dirt and stains.

POSSIBLE CAUSES:
Use of lower quality paint that is porous in nature. Application of paint to unprimed substrate.

SOLUTION:
Higher quality acrylic paints contain more binder, which helps prevent stains from penetrating the painted surface, allowing for easy removal. Priming new surfaces provides maximum film thickness of a premium top coat, providing very good stain removability.

ROLLER MARKS / "STIPPLE"

Unintentional textured pattern left in the paint by the roller.

POSSIBLE CAUSES:
Use of incorrect roller cover. Use of lower grades of paint. Use of low quality roller. Use of incorrect rolling technique.

SOLUTION:
Use the proper roller cover; avoid too long a nap for the paint and the substrate. Use quality roller to ensure adequate film thickness and uniformity. High quality paints tend to roll on more evenly due to their higher solids content and leveling properties. Pre-dampen roller covers used with acrylic paint; shake out excess water. Don't let paint build up at roller ends. Begin rolling at a corner near the ceiling and work down the wall in three- food square sections. Spread the paint in a zigzag "M" or "W" pattern, beginning with an upward stroke to minimise spatter; then, without lifting the roller from the surface, fill in the zigzag pattern with even, parallel strokes.

ROLLER SPATTERING

Tendency of a roller to throw off small droplets of paint during application.

POSSIBLE CAUSES: 
Use of exterior paint on an interior surface. Use of lower grades of acrylic paints.

SOLUTION:
Higher quality paints are formulated to minimise spattering. Using high quality rollers which have proper resiliency further reduces spattering. In some cases, a quality wall paint may be preferred for ceiling work, for maximum spatter resistance. Overloading the roller with paint will result in excess spatter, as will overworking the paint once it is applied to a substrate. Working in three-foot square sections, applying the paint in a zigzag "M" or "W" pattern and then filling in the pattern will also lessen the likelihood of spattering.

SAGGING

Downward "drooping" movement of the paint film immediately after application, resulting in an uneven coating.

POSSIBLE CAUSE:
Application of a heavy coat of paint. Application in excessively humid and/or cool conditions. Application of overthinned paint. Airless spraying with the gun too close to the substrate being painted. 

SOLUTION:
If the paint is still wet, immediately brush out or re-roll to redistribute the excess evenly. If the paint has dried, sand, and reapply a new coat of top quality paint. Correct any unfavorable conditions: Do not thin the paint; avoid cool or humid conditions; sand glossy surfaces. Paint should be applied at its recommended spread rate; avoid "heaping on" the paint. Two coats of paint at the recommended spread rate are better than one heavy coat, which can also lead to sagging. Consider removing doors to paint them supported horizontally.

SEALANT FAILURE

Loss of sealant's initial adhesion and flexibility, causing it to crack and/or pull away from the surfaces to which it is applied.

POSSIBLE CAUSES:
Use of lower quality sealant. Use of wrong type of sealant for a particular application (e.g., using acrylic or vinyl sealant in areas where there is prolonged contact with water or considerable movement of the sealanted surfaces).

SOLUTION:
Use a top quality water-based all-acrylic or siliconized acrylic sealant if prolonged contact with water is not anticipated. These sealants are flexible enough to adapt to minor fluctuations in the substrate, stretching in gaps that widen slightly over time. They also adhere to a wide range of interior building materials, including wood, ceramic tile, concrete, glass, plaster, bare aluminium, brick and plastic. Note: Silicone sealant should not be painted.

WRINKLlNG

A rough, crinkled paint surface, which occurs when uncured paint forms a "skin."

POSSIBLE CAUSES:
Paint applied too thickly (more likely when using alkyd or oil-based paints). Painting during extremely hot weather or cool damp weather, which causes the paint film to dry faster on top than on the bottom. Exposing uncured paint to high humidity levels. Painting over a contaminated surface (e.g., dirt or wax).

SOLUTION:
Scrape or sand substrate to remove wrinkled coating. If using a primer, allow it to dry completely before applying top coat. Repaint (avoiding temperature/humidity extremes), applying an even coat of top quality interior paint.

 YELLOWING

Development of a yellow cast in aging paint; most noticeable in the dried films of white paints or clear varnishes.

POSSIBLE CAUSES:
Oxidation of alkyd or oil-based paint or varnish. Heat from stoves, radiators and heating ducts. Lack of light (e.g., behind pictures or appliances, inside closets, etc.).

SOLUTION:
Top quality acrylic paints do not tend to yellow, nor does non-yellowing varnish. Alkyd paints, because of their curing mechanism, do tend to yellow, particularly in areas that are protected from sunlight.

Kindly supplied by Rohm and Haas - Paint Quality Institute.