has leeched into the slab itself. This way, the new coatings will bond into the slab and not sit on top - soon to delaminate. Traditional Acid stains may not work as they are reactive. This means they are reacting with the salt, lime and calcium in the concrete, changing their chemistry. If the porch was ever cleaned with an acid, the traditional materials may not react AT ALL. In this case, Behr sells a line of transparent acrylic paints which when applied with a sprayer gives an acid stained appearance. Here is a BIG TIP.... As these are transparents, whatever the base color is, it will blend with the transparent. A few weeks ago, after pressure washing the deck, we applied a "Chickory" brown to the deck. What came out was "Burgundy". NOT what the client wanted. This is why I say grinding is best. If the floor is ground, it will return to its natural white surface. Consider this as your starting point. This way the colors you apply will be closest to the look you are seeking..... GOOD LUCK !