Stain on concrete

Jan 9, 2018
Central Arkansas
Real Name
Cody Davidson

Customer had OLD paint (probably oil based based on how long it took!) on her driveway... 4000psi removed the paint - customer is thrilled... but there’s a stain where it used to be. Concrete being what it is I don’t expect it to completely disappear; any ideas what could lighten it for future reference?