When I was a kid I got a chemistry set as a present and I learned to make invisible ink using cobalt chloride and ammonium sulfate. After making two solutions, one with cobalt chloride and the other with ammonium sulfate you could write messages and after the paper dries you expose the paper to heat. Cobalt chloride produces a reddish color when heated and ammonium sulfate a yellow-greenish color.
thanks a lot for your answer.I'm interested in it.I'll try it.
Thanks a lot for your answer.I'll try it.
Lemon Juice as ink drys invisable and is viewable when heated over a flame. Sugar water does the same thing.
urine, it's free.
Wet a sheet of paper, put a dry sheet on top and write your message on the dry sheet. Let the wet sheet dry out and it is plain paper again. However if you wet it you can read the message.
For secret writing often a code may be the best way.