Concrete Etching can be done with various dilutions of Hydrochloric Acid depending on the age of the concrete/masonry and degree of etch required. A deep etch for mortar/concrete spatter removal may be performed with one-part Hydrochloric Acid diluted with two parts water. A moderate etch for old concrete with 1:10 dilution or1:20 is used to provide a very mild etch and for new concrete apply solution diluted to surface, broom out to spread evenly on surface. Allow approximately for 1 litre of diluted acid per square metre of surface. Allow to react or until bubbling ceases, then rinse with water to leave clean etched surface. Brick Cleaning is performed with a strong one part hydrochloric to two parts water solution or even neat Hydrochloric Acid if required