The results showed that the paper was written with lemon juice and wait until dry. When the light shines, you will see the message. But if not, it will not see the light shining because Lemon juice is acidic and weakens paper. When paper is heated, the remaining acid turns the writing brown before discoloring the paper.
Conclusion : If the paper is brought to a ight the message will become visible . If the paper is not brought to a lightthe message will stay in visible.