Why a solution of slaked lime is used for whitewashing walls but after two to three days of whitewashing and gives a shiny milky finish to the walls ?

A solution of slaked lime produced by the reaction is used for whitewashing walls. Calcium hydroxide reacts slowly with the carbon dioxide in air to form a thin layer of calcium carbonate on the walls. Calcium carbonate is formed after two to three days of whitewashing and gives a shiny finish to the walls. It is interesting to note that the chemical formula for marble is also CaCO₃ .
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Ca(OH)₂ (aq) + CO₂ (g) → CaCO₃ (s) + H₂O (l)
(Calcium hydroxide) (Calcium carbonate)