That is another reason for a whitening to develop. When those calcium ions slowly dissolve away, that process can also remove some color pigment too. That means something other than aggressive water is the culprit for porosity developing and a whitening effect to develop and increase over time. In fact, both elements can be dissolved by balanced water and even positive LSI water. Some people falsely assume that calcium hydroxide and calcium chloride can only be dissolved by aggressive pool water (negative LSI). Calcium carbonate, a primary plaster constituent, is insoluble. They are calcium hydroxide (a by-product of the cement/water reaction) and calcium chloride (if added to the mix). What leads to a porous, yet smooth surface? There are two relatively soluble components of hydrated (cured) cement/plaster. On the other hand, if the whitish discoloration is smooth to the touch, manifests itself in streaks, blotches, or small spots, and if diluted acid does not quickly remove the white discoloration, then one should realize that the problem is probably not calcium carbonate scaling, but a porous surface instead that is deteriorating faster than normal. It can be easily removed by scraping or sanding with sandpaper.

PorosityĬalcium scaling, which is caused by out-of-balance water (an overly positive LSI value), usually deposits a uniform layer of calcium carbonate throughout a pool and whitens the entire pool, including fixtures.

There is a direct connection in how white and pigmented plaster develops color-shading changes. It’s helpful to note that even common white pool plaster can develop white spots and streaks that are whiter than the surrounding plaster because of increased porosity in those areas. Boyd Clark, senior materials specialist with Construction Technology Labs, it’s the same reason that a head of foam is lighter than the beer the foam is lighter in color because it throws off more light: “The fact that we have a spot, or a lightened area is due to the fact you have an increased porosity,” he says. And when porosity develops and increases (which can take several months), a whitening of color/pigmented plaster results.Ī porous surface appears lighter in color because of the way it reflects more light than a non-porous surface. When calcium dissolution occurs, it means the plaster surface is deteriorating, losing density, and becoming porous. The whitening of colored plaster can also be caused by soluble calcium ions in the plaster dissolving and fleeing the scene into the pool water due to poor plaster workmanship and which has nothing to do with water balance. Here’s the workmanship issue that is both common and regrettably overlooked. But when there’s no scale there to remove, that will only cause etching, it won’t fix the problem and will shorten the life of the plaster. Once you make that misdiagnosis, it is then easy to mistakenly assume an acid wash is the best remedy. Because changes in color resulting from these defects are also a lighter or whitish color, it is easy to mistakenly believe that the problem is calcium scaling, and that the pool water has been out-of-balance. However, it is also common to have colored plaster (including quartz and pebble) surfaces lighten in color due to mistakes in plaster workmanship and material selection. As is widely known, calcium scale makes the surface rough and turns it white, and acid washing is often the remedy. First off, scale can be deposited onto pigmented plaster surfaces by out-of-balance pool water. Plaster colors can fade or turn whitish for a handful of preventable reasons. Later on, it must also be disappointing, if not more so, to learn that the cause of the unsightly color problem was misdiagnosed, and worse, the remedial action taken to resolve that problem caused more serious damage. That’s why pool owners are willing to pay extra to have that special color enhance their water and the entire backyard.īecause the interior pool surface is such a dominating visual element, it must be disappointing for everyone involved on those occasions when they watch their pigmented, colored pool become unsightly with whitish blotches, streaks, or small spots.

The color adds ambiance to the setting and can make the water wonderfully attractive and inviting. Having a beautiful pool with a colored surface, especially one with a quartz or pebble plaster finish, is a popular choice among pool owners, and understandably so. This is an EXCELLENT article on why colored pool plaster turns white, reprinted with permission from onBalance August 2020. Why Colored Pool Plaster Turns White August 12, 2020

Marcite pool plaster colors