Mortar is made by first heating chalk, then gently slaking and pulverizing the resulting hard material. Alternatively, slaked lime can be made from calcium chloride and lye (NaOH).
CaCO3 <====> CaO + CO2
calcite lime
CaO + H2O -------> Ca(OH)2
lime slaked lime
A solution of calcium hydroxide turns milky in the presence of carbon dioxide.
Most nonmetal oxides dissolve in water to form acids. for example,
CO2 + H2O ------> H2CO3
Carbonic acid
Carbonic acid is not found in aqueous solutions. Instead it is found as its equilibrium products:
H2CO3 + H2O -----> (HCO3)^- + (H3O)^+ and (HCO3)^- + H2O ---------> (CO3)^2- + (H3O)^+
Whitewash, a paint used historically to paint buildings and fences, was made from slaked lime and chalk. A few days after application to a surface, the slaked lime reacts with carbon dioxide in the atmosphere to form a hard surface. Unfortunately, the white wash rubbed off on clothing even after hardening.
Barn interiors benefitted from whitewashing because layers of whitewash smoothed the rough wooden and brick surfaces to ease cleaning, whitewash has antimicrobial properties, and flaking of the whitewash removed surface debris.
Efflorescence: Deposits of soluble salts on the surface of the masonry evident as a white haze. Moisture traveling through the capillaries of masonry may draw excess amounts of soluble salts along with it. As the moisture is drawn to the surface, it evaporates leaving the salt deposits behind. Efflorescence may be an indication that salts are present under the masonry surface called subflorescence, which is a more serious condition. Taken from: U.S. General Services Administration Historic Preservation Technical Procedures.
Identify the white flaky powder.
how did it get there?
CaCO3 <====> CaO + CO2
calcite lime
CaO + H2O -------> Ca(OH)2
lime slaked lime
A solution of calcium hydroxide turns milky in the presence of carbon dioxide.
Most nonmetal oxides dissolve in water to form acids. for example,
CO2 + H2O ------> H2CO3
Carbonic acid
Carbonic acid is not found in aqueous solutions. Instead it is found as its equilibrium products:
H2CO3 + H2O -----> (HCO3)^- + (H3O)^+ and (HCO3)^- + H2O ---------> (CO3)^2- + (H3O)^+
Whitewash, a paint used historically to paint buildings and fences, was made from slaked lime and chalk. A few days after application to a surface, the slaked lime reacts with carbon dioxide in the atmosphere to form a hard surface. Unfortunately, the white wash rubbed off on clothing even after hardening.
Barn interiors benefitted from whitewashing because layers of whitewash smoothed the rough wooden and brick surfaces to ease cleaning, whitewash has antimicrobial properties, and flaking of the whitewash removed surface debris.
Efflorescence: Deposits of soluble salts on the surface of the masonry evident as a white haze. Moisture traveling through the capillaries of masonry may draw excess amounts of soluble salts along with it. As the moisture is drawn to the surface, it evaporates leaving the salt deposits behind. Efflorescence may be an indication that salts are present under the masonry surface called subflorescence, which is a more serious condition. Taken from: U.S. General Services Administration Historic Preservation Technical Procedures.
Identify the white flaky powder.
how did it get there?