Is there a way I can make invisible ink?

Question

if not, where can I buy it

Answer 1

Lemon juice man.

http://chemistry.about.com/cs/howtos/ht/...

Answer 2

hydrated cobalt chloride disolved in alcohol is invisible until heated, then becomes invisible again when it cools.  It is easy to make at home but would take too long to tell you how and i'm lazy.

Answer 3

milk  works- then you hold it to a heat source like a light bulb or iron

Answer 4

Write using lemon juice....

Use heat to activate it (it will turn brown)

but it is invisible until then