"Hamilton Audio" wrote in message
news:KPJRd.434317$6l.361177@pd7tw2no...
It seems I underestimated the size of cardboard I needed to do a light
painting job. I've now got a nice faint black outline of that piece on
the garage floor.

I know it'll wear away naturally, but is there a faster/better way to do
it? Some chemical and a power spray?

bmoney

either the paint can be cleaned out of the concrete surface, or if it has
infiltrated the concrete enough you will have to remove a thin layer of the
surface concrete to get rid of the coloration

many concrete cleaners are available

if those don't work, removing a thin layer of the surface concrete can be
achieved with a pressure washer or the concrete surface can be etched with
acid, both should be done by someone qualified

if cleaning doesn't work and removal is not an option, covering up the
coloration could be achieved with some of the quickrete products available
in retail outlets, you might not be able to match colors precisely between
the garage floor and the patch, experimentation on an inconspicuous area or
extra concrete before making the patch cover is wise