I heat it directly on a glass stove and let it chill to the room temperature afterwards. I used it a few times (~10), had no problem so far. I am not sure this is the safest way to use it, at this price, you should take some precautions, such as boiling your starter in another vessel and then pour it back in the erlenmey. Still, this is very good for the price. The bottom is flat so it will stand by itself and it will allow you to use it with a stir plate. Enjoy!