I agree w/Steve. If the brush doesn't do it, I doubt the power washer will. Besides, if you get too ambitious, you may blow the morter out. Don't go too crazy with the brush. Brush a lot with little pressure, and slowly increasing it. Start on an inconspicious area in case it doesn't turn out right. Remember, brick has a hardened outer-layer. It's a protective layer, of sorts. If it's damaged sufficiently in your efforts, you'll accellerate its aging tremendously! (The inner's of a brick are soft and very succeptible to weathering.) This is why I suggest you work your way from light to heavy pressure w/o taking off too much brick. Remember, try this in an out-of-the-area spot.