Marjorie, Bentonite, a clay, has been used to seal earth dams, among other uses; it should work to seal the birdbath and should not be harmful to birds. Jack Thompson Conservation Lab Portland, OR [log in to unmask] On Mon, 30 May 1994, Marjorie W. Cleveland wrote: > The following question came from another bulletin board, but the > person asking for information received no response. > He has a leaky concrete birdbath, and is looking for advice on > how to seal the leakssafely, without poisoning the birds that > drink from the birdbath. > Anyone have helpful suggestions? >