Paint sheen is the glossiness of the paint finish. The glossiness affects the reflectivity, clean-ability, and the types of wall imperfections that can be hidden.
Flat paints are ideal for areas that are rough or have imperfections that need to be hidden. Light is not reflected from flat paints, so the variations in the smoothness of the wall are not as noticeable. Flat paints are not easily cleaned and can stain easily because they are more porous so they are generally used in areas that do not get dirty easily.
Primers are a type of paint that serve as a base coat for higher sheen paints. Gypsum wall board has a smoother finish than the drywall compound used at joints in the wall board. The primer helps to hide this difference and allows high sheen paints to look much smoother across the change in material.
Eggshell, Satin, Low-Luster Paint
These low-sheen paints offer a aesthetically pleasing finish that has more life than a flat paint. For this reason, many people paint their walls with an eggshell paint. The reflection from the paint highlights the texture that the paint picks up from the roller. The problem with these finishes is that they cannot be touched-up. When a hole is patched, or a mark needs to be covered, the painter must paint the entire wall to avoid "flashing", which is the difference in reflection that is caused from two different paint applications. However, eggshell paints are more cleanable or scrub-able than flat paints.
The middle-zone between gloss and low-luster paints, semi-gloss offers a more durable finish that resists stains better than less-glossy paints. The higher sheen also makes these paints less porous, so they are often used on walls, doors, or trim that tend to be touched by dirty hands or in wet areas.
Since the higher gloss level highlights imperfections, it is recommended that walls with semi-gloss paint have a Level 5 Finish. In addition, semi-gloss paints are prone to flashing and cannot be touched-up.
The highest sheen level are gloss paints. These are most resistant to stains and dirt. Due to their shininess, many people dislike the aesthetic. They are rarely used except in areas that need extra durability.
Gloss painted walls require a Level 5 Finish and cannot be touched-up.
Uses: walls needing extra clean-ability or durability.