Question

why we see shine white finshing on the wall after two two three days of white washing?​

Answer 1

we see white finishing on the wall because of the deposition of calcium carbonate.

calcium carbonate is mostly used for the whitewashing of walls because it gives a shiny appearance on the wall.

that is why even marble is made up of calcium carbonate.

thus in white wash calcium hydroxide is present it slowly comes in contact with the carbon dioxide present in the atmosphere to form calcium carbonate which gives a shiny appearance.

thus the reaction involved here is

ca(oh)2  + co2 =  caco3 = h20

Answer 2

The CaOH on the wall after two two three days of white washing reacts with CO2 in air to form CaCO3