Pool Info: Plaster Pools
Concrete pools are the oldest form of building pools. The process starts with digging a hole in the ground and lining the hole with rebar. Then the drains, skimmers, return lines, and in-floor cleaning system are set into place. After that, the pool is shot with gunite. Then, the tile and coping stones are set in place. Finally, the pool is shot and troweled with plaster. Once the plaster is finished, the company usually starts filling the pool with water.
Once the pool is full, the system is started up and balanced with chemicals. This is the time that takes the most work, usually a lot of brushing and backwashing due to dusting from the new plaster.
Also called whitecoat or marcite, plaster is an age old process of finishing many structures. Used underwater, it provides the watertight seal that the more porous gunite or shotcrete beneath it cannot. Plaster finishes provide twenty years of service under ideal conditions, however, ours is rarely an ideal world. The plaster surface is meant to degrade slowly, eventually requiring a fresh coat.
Plaster has shading variations?
Known as mottling, and distinct from surface stains and deposits, mottling may appear as grayish hued areas. Rarely do I see a plaster job that is white like milk. They're usually white like clouds. Being a natural product, mottling is inherent in any plaster job and should not be considered a defect. There has been much research on the subject in recent years, however no consensus has been reached on the causes and cure of mottling.
Plaster is stained?
Different from mottling, stains are usually localized and distinct in color from the plaster. Most stains are caused by heavy metal minerals coming out of solutions and depositing themselves on the nearest structure they find. They may also remain suspended in water, providing dramatic new color schemes. Below is a chart listing common metals found in pools, where they came from, and their identifying colors.
Plaster has crystalline deposits?
Your pool water has precipitated metallic salts out of solution. This will create areas of the pool which are extremely rough and scaly. There are several solutions to remove these deposits, including acid washing, sanding and the use of a calcium deposit dissolving chemical called HydroQuest.
If any of the above causes apply to you, your pool should be using a sequestering agent which aids your water balance in preventing the metal from dropping out of solution and staining underwater surfaces. Most stains left by precipitated metals can be removed by one form or another. An acid wash every few years will keep a pool looking nice. (continued)