Hi, another "newbie". I have been doing stained glass for over 30 years and now want to try mosaic. We just recently moved to FL where there is a cement birdbath outside our house in the garden. (my inspiration). It is pretty dirty, mildew and such. I imagine I would need to clean it real good before attempting to do anything to it. I did find a good website that helps me get started on basic mosaic tech. but not in how to clean it. Any ideas? I was thinking bleach and a good stiff brush. After I get it clean, should I seal it with anything before getting started. Thanks for any help you can give me.