Our first try fails, it lost 15 celsius, but on second try we used one more layer of aluminium foil. Then we lost 10 celsius, it was successful. Then we add neoprene. When we had the third time, our heat lost 7 celsius. Our hardest thing to do is to decide the materials that we will use it. Sometimes we have different ideas like when I said mylar my partner think we need to use bubble wrap. We used these items because these materials can all keep the transfer of heat or cool. They are an insulator and it is a poor conductor. the main material that we use is mylar. I think the most keep warm material is mylar. The quality of this cup is not bad, there is too thick.  I want to change the lid because there are too many pieces of cotton I will make a fence surrounding the cotton and aluminum foil.