All of our flasks are made from borosilicate type glass which is nice because they can be transferred directly from heat to ice and not crack like normal glass. (We do not recommend the use of an electric element. If this cannot be avoided, we recommend using a larger pot as a hot water bath on the stove.),,Great Flask for yeast culturing.,,Recommended Process for Use of Flask:,Double Boiler Method,,It is important for your safety to heat water in the flask with a heat source that distributes heat evenly. Our manufacturer has confirmed that direct heat to the glass can break down its integrity and break if the heat source doesn't distribute evenly.,,Morebeer! recommends using the "double boiler method."  This process involves using a boiling water bath on the outside of the flask to heat up the water inside the flask.  All you need is a kettle 3 gallons or larger.  This process is much safer and efficient. If the flask should break or boil over, your kettle will be there to collect the contents, thus keeping your stove clean and keeping you away from potential harm.  ,In the lab world, these flasks are known as "Student Grade". A great flask for making yeast starters! (Student grade is not the highest grade flask and will have minor defects),