What material has the lowest melting point? I'm doing an interesting research project of finding an invisible ink. My purpose is to find a material on which I can write on and has a very low melting point. I want to write on this kind of material by using my invisible ink. From my research about the invisible ink, I know that to develop the ink, heating the document will be the first method that everyone can think of. Therefore, I want to find a low melting point material to prevent my secret ink from detection which means the material will burn immediately when someone tries to heat it. I really don't know what material is my first choice. So I come here to seek for answers. Plastic is better. Thanks a lot.