Stucco Manufacturers Association Efflorescence

1 StuccostuccoStucco2402 Vista Nobleza, Newport Beach, CA 92660 PHONE FAX Manufacturers AssociationSpecifically in the plastering industry, Efflorescence describes the manifestation of a powdery coat covering the surface of the Stucco finish. Definition: Efflorescence refers to the crystalline deposit,usually white, that may develop on the surfaceof integrally colored exterior Portland cementplaster finishes. Efflorescence often occurs during periods of damp, wet and cold may also occur after the fog-coatingprocess due to the additional moisture added tothe wall.

2 Efflorescence often occurs right afterthe completion of the building project, but thisis not a definite rule as Efflorescence can occurand reoccur at any time as long as the conditionsfor its manifestation are not eliminated orreduced from the exterior wall in of Efflorescence : Efflorescence is the manifestation of a process:water dissolves salts present within a substrate,this salt solution migrates to the substrate s surface, and a salt deposit remains after thewater evaporates. Efflorescence is not normallydue to application or faulty materials.

3 Rather, itis an unfortunate manifestation of a combinationof various factors and events that sometimestake place together at the same time despitehuman efforts to contain/prevent forms of Efflorescence have been identified:primary and secondary. They are distinguishedby the point in time at which they occur in rela-tion to the curing process. Primary efflorescenceoccurs during the curing process. Excess water in the wet plaster matrix bleeds to the surfacewhere it eventually evaporates, leaving behinddeposits of crystals.

4 Primary Efflorescence isoften the culprit responsible for the whitebloom or the new building bloom observed innewly constructed buildings with fresh and wetstucco walls. Secondary Efflorescence occurs incured Stucco walls that are in cyclical contactwith moisture or are subjected to cycles of re-wetting and drying. In this case, the incidentmoisture penetrates into, and leaches from, thematrix, dissolving soluble salts remained as by-products of the cement hydration process. Uponsubsequent drying and wetting cycles, the watercan migrate back to the surface and carry with itthe dissolved salts.

5 Once at the surface, thewater will then evaporate and leave behind onceagain unsightly deposits on the surface of two forms of Efflorescence and how theymanifest explain the reason why most efflores-cence can occur immediately upon the completionof a building project, while other efflorescenceoccurs much later on in , in general, can occur on masonry, concrete,brick, and Stucco surfaces, among others. Efflorescence , as aproblem, has been studied and reported on for more than 100years. A technical bulletin by T. Rishie, issued by the Divisionof Building Research of the National Research Council, Ottawa,Canada, stated that the following compounds can be found inefflorescence: Sodium Sulfate, Sodium Carbonate, SodiumSilicate, Sodium Bicarbonate, Potassium Sulfate, CalciumSulfate, Calcium Carbonate, and Magnesium Sulfate.

6 There canalso be chlorides, nitrates, and other salts in addition to thecompounds listed above. For the plastering industry in particular, it is a well-acceptedfact that the white crystals formed on the surface of the Stucco walls, or Efflorescence , are often Calcium Carbonates(CaCO3) crystals. When excess water in the wet plaster matrixbleeds to the surface, it eventually evaporates and leavesbehind deposits of calcium hydroxide crystals (Ca(OH)2), whichreact with the carbon dioxide (CO2) in the air to form CalciumCarbonates (CaCO3).

7 There is a common misconception thatefflorescence can only occur at the bottom of the wall, ascommonly seen in the case of brick or concrete walls. Thetruth is this type of Efflorescence can occur anywhere on the surface of the Stucco walls, and it is not limited to certainsections of the the process of Efflorescence to occur, four things must be present: a) Salts:Salts are very common minerals occurring in earthenbuilding materials everywhere. Mixing water in the field canalso contain minute quantities of salts. Sand and lime manu-factured from various locations can contain different typesand quantities of soluble salts despite the manufacturer seffort to eliminate them from their products.

8 Quantities ofwater-soluble salts as small as a few tenths of one percent aresufficient to cause Efflorescence . For the plastering industry,hydrated cement contains a substantial amount of calciumhydroxide as an inevitable by-product of the reactionbetween cement or lime and water. Another source of solublesalts is the soil in contact with basement and retaining sources of Efflorescence may be seawater exposure orprevious attempts at cleaning that did not completely removecontaminants from the ) Physical Forces: Efflorescence is particularly affected bytemperature, humidity, and wind.

9 Physical forces such aswind can force water into a building substrate. The movementof wind over the surface of a building can create pressure differentials that cause the water to move upward. Capillaryaction can cause water to move upward and laterally within a substrate. Hydrostatic pressure present under below-gradeslabs and behind below-grade retaining walls can also causewater and/or water vapor movement. These physical forces, as well as others, can increase the absorption of water thatleads to ) Moisture:Whenever water is present, the potential forefflorescence increases if latent salts exist in the substrate,and/or an external source of salt is present.

10 Repeated cyclesof water saturation and evaporation cause salts to migratefrom the substrate and Efflorescence occurs. Precipitation, both during and after the construction process,encourages Efflorescence . Efflorescence most often appears on buildings after long periods of precipitation during coolweather. During such periods, walls become increasingly satu-rated from the outside to inside. A building s warm interiorcan encourage such saturation. Voids in the substrate can alsobecome extremely saturated with water vapor.