As Jim says, consult a Brick Mason BEFORE you do anything. You may not know this but brick needs to BREATHE! It's a pourus product that absorbes and exhales water vapor. By sealing it, you will severely increase the aging process and do damage to the brick. DON'T DO IT! DON'T sandblast either. The interior of the brick is softer than the exterior. It's a product that's been put in a kiln (or fired) when it's made. Learn about brick before you go messing w/it.