After preparing starters in a kettle and the transfer hot wort to no-name Erlenmeyer flasks and then cool them in an ice bath we started to experiment with boiling DME in the flasks with direct heat (gas) which ended in disaster, we decided to go with some well known Pyrex Erlenmeyer flasks and halogen hobs and they work great together. Sterilization and boiling at the same time, perfect!