# Question 684ed

Jun 21, 2017

You whitewash with a calciumhydroxide emulsion, also called slakes lime Ca(OH)_2)#

#### Explanation:

Through contact with carbondioxide in the air, this changes into calciumcarbonate $C a C {O}_{3}$:

$C a {\left(O H\right)}_{2} + C {O}_{2} \to C a C {O}_{3} + {H}_{2} O$

Of course the change happens from the outside in, and the complete process may take much more than a few days, but the calcium carbonate tends to crystalize, and this often gives a shiny finish.