Endospores are designed to withstand the harshest of conditions. Boiling water at 100 degrees C will kill many bacteria but will not eliminate all endospores. A much more effective sterilization technique is to autoclave whatever it is you are trying to sterilize. An autoclave is a machine that heats the sterilization chamber well beyond 100 degrees C and applies intense pressure inside the chamber, which helps in the sterilization process. You can autoclave something for at least 30 minutes and be confident that your sample will come out sterile. Be careful, though, because unless your materials are designed to withstand intense heat and pressure, they may melt (I'm speaking from experience!). Whichever technique you choose, the longer the time of exposure, the better the sterility will be.
