Re: Effects of water on bronze
The effects of water on bronze in a fountain application will vary greatly on the overall circumstances. Just like getting a consitent chemical patina on bronze, seemingly insignificant elements can make a big difference. The main thing is to know your alloys. In my experience silicon bronze holds up the best in fountains. Cheap castings with a lot of zinc or tin or other such metals can cause real problems. Metals tend to migrate in solution. Over time elements within your alloys may migrate out or onto your sculpture. This includes every piece of metal in your plumbing as well. This usually not a big deal for a well cast piece with a traditional green/brown patina, however don't expect your piece to stay the same color as the first day you applied the patina. For this reason it is usually best to stay away from the fancy colors and stick with the range that is closer to natural oxidation of bronze. Perhaps a bigger potential problem is mineral build up. When water evaporates on the surface it leaves a small amount of minerals previously suspended in the water. Given enough time this can look like a moldy fungus, which incidentally would be the next potential problem since the coarse surface of the minerals gives algae and mold a place to hang onto. The bond of mineral to metal gets stronger over time and at some point the only way to clean the piece is to sandblast and re-patina. I've heard tell of various water additives developed in recent years that are supposed to reduce this problem but have not personally tried any out. High mineral content is problematic here in the southwest. Pond water will likely have its own peculiarity. Clorine in the water will reduce algae but also accelerate the 'greening' of your bronze sculpture. Muriatic acid will help keep the minerals in check but will also destroy your patina almost instantly. Chemical additives also can be detrimental to plants and wildlife in the pond. If the piece is intended to be cleaned periodically it is best to design the installation so that the piece can be removed from the pond to avoid contamination by hazardous ceaning solutions or processes.