Does a one-way view-able ink exist for writing on windows?

[Doppel]

Does anything like this exist? Specifically I want the ability to, for example, write something on a car window that you can see if you look at the car but that if I look out the window I completely cannot see.

Yes, I realize if such an ink or process does exist (and I don't think it does; because even public buss ads that "fake" this are using strange screens to do so) it would be complex but I don't think it's physically inconceivable.

😎

 

[DrPizza]

I think that the answer to your question is... yes and no. To understand how it could be done, see this:
http://www.howstuffworks.com/question421.htm

Thus, your one-way viewable ink would work during the bright part of the day, but not at night.

 

[sdifox]

the perforated screen thing works fairly well, just don't cover your windshield.