Removing tool marks - Hydrochloric Acid

["Ken Johnson" <kejohnsn@xxxxxxxxx>]

Hydrocholric acid can be quite dangerous. It is reacting with the calcareous
portion of any stone (concrete and mortar, being calcium based, are attacked
as well).  The fumes given off are chorine gas -- mustard gas for any of you
WWI vets. Nice yellowy gaseous corrosive stuff to eat out your lungs and
bronchails.

As it reacts it leaves a salty residue - calcium chloride being one
constituent. This will promote steel corrosion.

If you must use acid - rinse well - protect eyes, skin and lungs. If you
want to apply to a localized, controlled area, mix the acid with a
thickener, Cabosil or similar used in the fiber glass industry.

Hydroflouric acids should work on silica. Phospheric acid will remove rust
stains from most stone but always test on a chip or piece of waste before
using to ensure you will not damage the stone.

However - you could buy a small grinder with a dust attachment - use Zec
discs and remove the rough marks.

Ken Johnson
Victoria, BC