Working on revovating my Mother's basement. We pulled up rubber backed
carpet that had been down at least 40 years. This left a lot of rubber
carpet backing and glue stuck to the concrete. Scraped and scrubbed until
the floor looks and feels like clean concrete but it is still stained black
by what was there before. I had wanted to use a stain on the floor but I'm
now thinking I'll have to paint it. So the question... do I need to use
some kind of primer on the floor to seal the black stain so it doesn't bleed
up through the paint...and if so, what kind of primer?

Tom G.