Cleaning the mortar
The man cleaned the mortar with a solution of 20% muratic acid/80% water and a stiff brush. This removed the any mortar residue and hazing from the brick. It’s important to use protective gloves when working with this solution as it is very caustic. Also, you must ventilate the room depending on the size area you are working in because the fumes from the acid can be noxious. You can seal the wall if desired after the wall has dried from the cleaning.