my wall was painted and I did removed the paint using some chemicals, then I ask a professional company to come over and clean the bricks with acid the result was so bad very bad.
I ask some other company to do a test and leave the wall in one colour but they could not do it.
and the only way to have it right was to grind it. Now is good but a bid fade colour. maybe Yacht Varnish is a good solution...
thx