Consumer Glossary of Terms

The following Glossary is intended to assist the consumer in understanding the terminology used in the pool plastering industry. These terms should help when discussing your pool project with your pool contractor and pool service providers.




A liquid or dry chemical used to lower the pH and or the alkalinity of the pool or spa water.

Acid Wash

1. The cleansing of the interior finish surface by dissolving the material on a cementitious coating’s surface to remove efflorescence, dirt, or other unwanted stains. 2. The process of etching a cementitious coating’s surface in order to expose the aggregate or sand to create the exposed aggregate finish. 3. The use of low-strength (diluted) acidic solution used for removing certain cementitious stains, dirt, precipitants, or marks, whereby the stains are removed with little, if any, of the cementitious surface being compromised.

Adhesion Bond

The ability of a hardened cementitious coat to hold together with the substrate.


A separate component that is mixed with the cement, aggregate, and water that adds a beneficial characteristic to the material.



Bond Coat


A mineral added to pool water to help stabilize pH and alkalinity.


Calcium Hardness

A measure of the amount of calcium dissolved in water.

Calcium Carbonate

A calcium compound that is a major component of scale.

Carbonate Alkalinity

The measure of the carbonate and bicarbonate negative ions in a solution.

Calcium Hydroxide

A soluble white crystalline material, commonly known as ‘plaster dust’, that is apparent when the pool is filled with water after a new interior finish has been installed.


A powder that when mixed with water and aggregate hardens to form the interior finish.


Having the properties of cement.

Continuous Fill

Filling a vessel with no interruption of flow until the water reaches the perimeter tile. (Note: time of fill depends on whether it is a white plaster, or other finish that may require next-day prep prior to fill.)


The act or process that ensures enough water is available for the cement binder to continue to react, harden, and gain strength.



See Delamination. (Note: terms are not the same thing.) Debonding is a separation of one material from another material.


The separation of a material from itself or from the substrate.



Soluble compounds, predominantly calcium hydroxide, which migrates in the presence of moisture, from within a cementitious product to the surface followed by the precipitation and carbonation of the soluble compounds onto the surface.


1. The physical or chemical removal of material from within the surface of the interior finish. 2. The visible pitting of the surface of the interior finish due to chemical or physical processes. 3. Any chemical or physical action on a surface that is capable of removing or dissolving away elements or compounds of that surface.


Fill Water

Source water used to fill a pool.


Typically referring to the floor returns, wall directional returns, or in-floor pop-up cleaning heads that direct the flow of water returning to the pool.

Free Chlorine

That portion of the total chlorine that is not combined chlorine and is available as a sanitizer.



In cementitious materials, the chemical reaction between hydraulic cement and water.

Hydration Discoloration

The normal discoloration of the finish due to variations within the finish coating, such as differing levels of humidity, temperature, or thicknesses. The abnormal discoloration of the finish from locked hydration reaction from the cement or other components of the finish coating.



Independent Pool and Spa Service Association

Interior Finish Application

The plastering of the substrate structure of a swimming pool with a cement-based product. (Note: interior finishes for swimming pools have no structural rating, meaning they are not considered as part of the swimming pool structure.)


Langelier Saturation Index

A method of calculating the degree of saturation of water as related to calcium carbonate solubility. Knowing the calcium carbonate solubility can be used to predict whether water has a tendency to precipitate (scale) calcium from the water onto the finish, or whether the water has a tendency to dissolve (leach) calcium from the finish.


The extraction of a mineral or metal from the interior finish.


Manual Placement of a Pool Finish

The placement of an interior finish without the use of specialized equipment, i.e., using a wheel barrel or bucket.

Metal Staining

A metal precipitate that forms on the interior surface and others surfaces of the swimming pool from a significant concentration of metal ions in the water.

Mineral Scaling

A scale formed on the interior surface of swimming pool from mineral precipitation due to chemical imbalance.

Moisture Migration

Moisture passing through the substrate of the structure.


1. The blotchy appearance across the surface of a cementitious finish, which can have varying shades of color, usually in a random pattern and are typically more pronounced in darker colored finishes. 2. The normal variations in a cementitious material as a result of the ongoing hydration process, which typically lessen or disappear over time. 3. The abnormal discolorations associated with trowel burn, trapped moisture or other situations that do not resolve themselves.

Muriatic Acid

A commercial name for hydrochloric acid. Used to adjust pH and alkalinity lower and used to acid wash swimming pools.


Negative Edge

A design feature incorporated into a pool wall wherein the water flows over the wall (edge), into a catch gutter or catch pool, creating the illusion that the water vanishes. Also known as an infinity edge or vanishing edge.


Northeast Spa & Pool Association


National Plasterers Council


Perimeter Tile

Water line tile.


A value used to express whether pool water is in an acid or a base mode, expressed as a number from 0 to 14 (Note: based on the negative log of the amount of H3O present in the water).


Pool and Hot Tub Alliance

Plaster Dust

Pool Maintenance

The physical and chemical treatment (balancing water) of a swimming pool.

(Plaster) Interior Finish

A combination of cement, aggregate and water, with or without other admixtures, that is mixed, placed, and finished in a manner that forms a desired interior finish for swimming pools.

Pool Water Chemistry

See Water Chemistry. (Recommended Ranges.)

Pool Water Test Kit

The kit used to test pool water.

Pneumatic Placement of Materials

The moving and placement of construction materials by air.


Return Lines

The piping that is referred to as effluent, returning water to the pool or spa.


Scale (Precipitate)

1. A mineral compound that precipitates out of solution by chemical or physical reaction. 2. In a swimming pool, it is the minerals/and or metals that come out of solution and adhere to tile, interior finishes or other surfaces, resulting in unsightly stains and roughness.

Semi-Permeable Membrane

A term typically used in the industry referring to interior finishes that are watertight but still allow water vapor to pass through.


A chemical that combines with metals and minerals, keeping them in solution and preventing them from depositing on and staining pool surfaces. (Stain preventor.)


1. The substrate structure of a swimming pool that is either formed concrete, shotcrete wet, shotcrete dry (also known as gunite) sprayed on the steel structure grid (rebar). 2. The substrate on which the interior finish is applied.


A pneumatically applied mixture of sand, cement, aggregate, water, and pump nozzle where air is added. (Known as Shotcrete Wet, and Shotcrete Dry (gunite).)

Shrinkage Crack

Cracks that develop during application or within twenty-four hours after final set.

Start-Up Procedures

The necessary procedure used to start up a freshly plastered pool.

Start-Up Technician

A person who starts the pool equipment and often adds the initial chemicals to the pool water. They may also be tasked with teaching the homeowner how to care for the pool.


See Shell.

Substrate Cracks

Cracks in the underlying structure.


Tile Line

Total Alkalinity

The total amount of all alkaline materials in water. It is principally the water’s carbonate system and is the resistance to change in pH and the buffer against acid attacking the interior finish.

Total Chlorine

The sum of both free and combined chlorines.


A tool used to apply and finish cementitious products.


The hand application, distribution, consolidation and finishing of the surface coating.


VGB (Virginia Graham Baker)

VGB Pool and Safety Act, which requires that all swimming pool or spa drain covers manufactured, distributed, or entered into commerce in the United States conform to the entrapment protection standards of the ASME/ANSI-A112.19.8 performance standard, or any successor standard.


Water Chemistry (Recommended Ranges)

The recommended levels are stipulated by PHTA and the NPC for pH, calcium hardness, carbonate alkalinity, cyanuric acid (stabilizer), sanitizers, and total dissolved solids that are known to protect bathers/swimmers and the interior pool finish.

Water Feature

One or more items such as waterfalls, fountains, and bubblers.

Water Vapor

The gaseous phase of water.


Material or structure that inhibits liquid water, humidity, and water vapor.


Material or structure that inhibits liquid water. (Note: Liquid water will not penetrate through the material, but water vapor and humidity will slowly penetrate the material over time.)


The process of covering, treating, or applying a coating to a structure to keep moisture from penetrating. For swimming pools, these are typically proprietary systems.