About 70 percent of the Earth's surface is water-covered.  We all understand that salt water from the ocean would not be good for mixing with metalworking fluids, but there is plenty of fresh water around so why be concerned?  Metalworking fluid demands good quality water for stable emulsion.  How does salt or hardness affect mixing of metalworkng fluids?  What are the permissible limits of chlorine and chlorides?  STLE's John M. Burke discusses the importance of water in metalworking fluids.  This article appears on the STLE website, under RESOURCES.