Writing that only appears under heat or light is read as a hidden message waiting for the right moment. Tradition links it to secrets, unspoken feelings and truths that need the right conditions to show.
Has this come up in your dreams before? What was going on in your life then?
My Cosmic Code has a private dream journal. Write a dream down and the app picks out the symbols in it, shows what dream books say about them and, over time, which words recur across your entries. The journal is stored on your device only.