Does Adding Water to Semi-Gloss Paint Make It Flatter?

About Sheen

• A paint's sheen is defined as how much shine it has. Paint sheen can be flat or matte, which has little or no sheen, to glossy or high gloss, which has a lot of sheen, or somewhere in the middle. Semi-gloss falls somewhere in between flat and high gloss paints, usually closer to high gloss. But there are no industry standards stating how much shine a paint must have to be classified as "semi-gloss." What one paint manufacturer defines as "semi-gloss" another may define as "satin." Manufacturers may even come up with their own term for it.

About Paint

• Paints contain a variety of ingredients but the three main ones are resin, solvent, and pigments. The resin defines the paint's sheen. The more resin in a paint, the shinier it is. The solvent dissolves the resin. Water-based and latex paints use water as their solvent, while oil-based or alkyd paints use a type of oil as its solvent. The pigment defines what color the paint is. So, based on this information, it would seem that adding water to water-based paint would reduce the amount of resin in the paint and make it flatter, but that is not how it works.

The Drying and Curing Process

• Although water is contained in water-based paint, it is not part of the paint. It is there to help transfer the paint from the can to the surface. Once the paint has been applied, the water evaporates and leaves the paint behind. This drying process helps the paint stick to the surface and create a durable bond. It takes about two to four weeks for the water to totally evaporate from water-based paints.

Adding Water

• Usually paints will be ready to use right out of the can with no thinning required. In fact, unless you know what you are doing, adding water is a bad idea. If paint is too thin it may dry too slowly, which may lead to peeling and blistering problems later on. Unless the paint is so thick that it is hard to work with or it is not going on smoothly, avoid thinning the paint. If you do decide to thin it, use a thinner designed for latex paint rather than water from your tap.