USAGE: We recommend you use a 3-5 gallon stainless kettle to heat the flask in. Put two inches of water in the kettle and then place the full flask inside the kettle. Softer to heat the flask in this manner, protecting both brewer, stove, and Flask. Then whole kettle with flask can be brought to the sink and cooled while the flask remains inside the kettle. The one drawback is that we have not been able to find the correct size stopper for this. The largest stopper we have is the Universal Large, which will stay in place with an airlock but does not fit snugly. We had to wrap two layers of cellophane around the bung to get an airtight seal.