Invisible Ink

[Rik]

Gary Bouton asks an interesting question in his signature.

How do you tell when you've run out of invisible ink?


My answer is: You rub Lemon juice where you want to check, and if it's blank, then you've run out of invisible ink!

What's your answer?

[wizard509]

For some invisible inks if you hold the paper to a heat source such as a light bulb the ink will turn brown same as happens with lemon juice.

So if you use lemon juice as an invisible ink how would you test that?

answer: heat.

[zaphodeist]

Doesn't Gary mean the invisible ink in the bottle?

[wizard509]

Doesn't Gary mean the invisible ink in the bottle?

Maybe but what fun is that?

[zaphodeist]

If it is what Gary meant then a method to tell could be devised. Same fun only finding the ink not the writing

After all, if you write the message without testing whether the invisible ink is in the bottle how do you check it? Your methods are correct but you'd have to write the message again ... and then the secret police would have got you

[simsmj]

You just have to weigh the ink bottle, or shake it to hear or feel the ink slosh! After all, how did you know it had any ink when you bought it.

Mike

[The Alien]

What if someone replaces your invisible ink with invisible water?

[wizard509]

If it is what Gary meant then a method to tell could be devised. Same fun only finding the ink not the writing

After all, if you write the message without testing whether the invisible ink is in the bottle how do you check it? Your methods are correct but you'd have to write the message again ... and then the secret police would have got you

Oh great, first Mr
But James took care of him

Now the secret police. Sheesh!

A float should be an accurate indicator of any fluid in the bottle invisible or not but that wouldn't answer the question of what kind of fluid.

How about something like a litmus paper to test what kind of fluid.
This might be something for a challenge to design an invisible ink detector.

[Mike Bailey]

The question: How do you tell when you've run out of invisible ink?
The answer: It will appear.

[wizard509]

The question: How do you tell when you've run out of invisible ink?
The answer: It will appear.

Would it? If it were gone then how could it appear?

Unfortunately we can't get

Mr.
after you because James locked him up. Lucky you.