Can I use polyurethane to seal a brick fireplace hearth? All the old paint was scraped off the brick leaving it a natural look and I just want to seal it with something that protects it and gives it a slight sheen.

Most brick sealers are designed to repell water. Waterproof brick and masonry with DEFY masonry waterproofing products (http://www.saversystems.com/masonryproducts.php) I don't think I'd go with a standard poly because it may not fare well with the heat of a fire.

I do not have the answer either, and am asking the same question - what can I buy to put on my bricks with a brush that will seal these bricks but will be safe when there is a fire in the fireplace?