Hi Tina - I use my EasiYo thermos, but just pour boiling water in to heat the thermos up, then I tip it out and put the plastic jar in and replace the lid. I think someone else said on here or somewhere else (who knows now with 21 pages to read through LOL) that the reason that you put boiling water in the EasiYo is that you start with cold water and a mix when making it using the sachets. Try it without boiling water in and see how you go