On Thu, 28 Aug 2014 14:01:05 -0700, RobertMacy
wrote:

On Thu, 28 Aug 2014 13:25:56 -0700, Oren wrote:

On Wed, 27 Aug 2014 21:58:28 -0700 (PDT),
wrote:

simple,Green scouring pad and a little water if it takes more than
that then use a 120 grit Sandpaper these are stains they don't just
magically disappear I've snapped lines that were bogus and tried to
cleaning them off minutes later and they were extremely hard unless you
have a little water and Green scouring pad it works like 400 grit
sandpaper and if its been in there for a long time you may need to go a
little more aggressive with sand paper yeah that takes some elbow
grease it's a stain most times when you snap lines on a slab you want
them to be permanentbecause they're usually being covered up by framing

Bah. Some chalk is more permanent than others. You have to pick the
correct one for the task. It may wash off easily or last longer; like,
say by walking on a concrete foundation ready for walls. YMMV

Isn't chalk a calcium based compound, therefore a 'fast' wash with
muriatic acid [too fast to eat the concrete] remove it a bit better?
Coloured "chalk" isn't "shalk" I think some of it is more closely
related to laser printer toner!!!