Do I need to reheat the Culturing Flask? We recommend that you reheat the flask after 12 hours as the flask will naturally lose a bit of heat over time. Keeping it at the optimum temperature will provide a thicker product with a more intense flavour. Related articles What kits can I use the Culturing Flask for? Do I have to use the Mad Millie Jar with the Culturing Flask? Do I have to heat my Yoghurt Culture? Can I not just put it into milk? How to Guide - Greek Yoghurt