Is there a substance or solution that can be put on paper or an object that would not be visible no matter how much you added on there. But you would be able to use filters to see the solution or substance. Anyone know anything that would work like this?

do you mean something like the UV security marker pens?

There might also be clear materials that polarize the light, and would be visible only with a polarizer.

how does a polarizer work? and any ideas on these materials?

A polarizer passes only one orientation of the electric field of the light. Most light undergoing specular reflection (e.g. a smooth surface, as opposed to diffuse reflection) will be polarized, so any transparent material that would give you this would show some effect. (it's why polarized sunglesses reduce glare - reflections off of your car, or water, tend to be polarized)

 

Birefringent materials would be different under the different polarizations, but that relies on light transmitting throught the material, not surface reflection.

http://en.wikipedia.org/wiki/Birefringence

 

But I think YT's suggestion of UV ink is the most straightforward.

Hellooo...

 

Could you tell us exactly what your looking for. In other words is this a practical question of just a thought experiment. Because though I hate to bring up the obvious, but how about water with a little bit of lemon juice. I hate to tell you, but I don't know many ways in which filtering light can produce an image from an already colorless surface.

 

Here's the reason in my thinking. white light is made up of all colors. When those hit a surface such as white paper all the colors will be reflected. Now say if you used iany color filter... lets take blue. All other colors would be absorbed so everything will look blue.

UV chemicals however may look colorless under normal light, but when a higher frequency of light is added if glows. Here light is added and not filtered. The only way a filter would help is if the original paper and righting were not colorless. Otherwise they could not be seen on the visible spectrum. Am I correct?

how does lemon juice and water work?

 

I need the solution or mixture to work on red or blue paper for now. would a UV chemical show up when it is viewed under UV light though (im guessing it would)?

First you mix lemon and water....

 

Then you take a quitip or something and write on the paper

 

Invivible...

 

Heat the paper to see the message...

ok, i knew that, i was just hoping that it was something you could see with filters only or something.

Nope. Only if there are mutiple colors in the paper..

For example:

Say if you had blue paper with tiny red dots spelling hello... invisible to the naked eye... Now you hold up a blue filter and the red stands out like christmas light.

how would i make the tiny red dots? just with a pen or something?

try it and see...

Put it on the back of a card or something so that the magician can read the card with red colored glasses

ok, thanks