Even someone who’s never seen a gallon of house paint can get a pretty good idea of the difference between a flat and a glossy paint. But how about platinum, melamine, velvet, pearl, silk, suede, low sheen, low luster...and more than 30 other names. That’s what the Master’s Paint Institute found when they investigated the offerings available between flat and semi-gloss finishes.
Although people have a pretty good idea of what a “glossy” surface looks like, without some kind of measurement procedure and reference standard, there’s no way of comparing one person’s conception of glossy to another’s conception. Enter the American Society of Test and Measurement, or ASTM, with a Standard Test Method for Specular Gloss. The standard involves shining a light on a surface at an angle of 60 degrees away from perpendicular, and measuring the amount of reflected light at an angle 60 degrees on the other side of the perpendicular. Higher reflection is higher gloss.
The Master’s Paint Institute has proposed standard categories for paints of different gloss finishes. For example, a flat paint would be at gloss level 1 (G1), with an ASTM reflectance measurement of 5 units. A high gloss paint would be at G7, with an ASTM measurement of more than 85 units. On this scale, an eggshell paint would be G3 with a reflectance between 10 and 25 units, while a semi-gloss is G5, with reflectance between 35 and 70 units. That all sounds pretty good, which is why this standard has been adopted by the U.S. Department of Defense as part of its Uniform Facilities Guide Specifications, the government of Canada, the Veteran’s Administration and the American Institute of Architects.
Just because a standard exists, however, doesn’t mean it has been universally adopted. Manufacturers are free to label their paints with any name they wish. So one manufacturer’s semi-gloss can be another’s pearl. In the early 2000s, the Master’s Paint Institute measured eggshell offerings from eight different manufacturers and found that none had a gloss reflectance level even as high as 10, while many had levels lower than 5 units — which most would consider to be a flat or matte finish.
Why it Makes a Difference
According to the Master’s Paint Institute Maintenance Repainting Manual, high gloss finish provides more physical and stain resistance than lower gloss finishes, but it also enhances textures or defects on the underlying surface. PaintPRO Magazine suggests that paints that fall between semi-gloss and flat tend to impart more warmth and depth to surfaces than do flat paints, while flat paints tend to conceal surface imperfections better than paints with higher gloss levels.
The name of the finish alone means very little. However, many manufacturers specify the measured gloss level. If you’re looking for an eggshell finish, look for a gloss level between 10 and 25, and look for a level between 35 and 70 for a semi-gloss paint. But, as with so many other aspects of paint, the best thing to do is paint a test area with your different choices and see which fits your needs in a given area.