diagnose the difference between paper and plastic

[canarybird33]

Hello.
I want separate this three things : pieces of paper , plastic , glass.
Is there any sensor to do this task?(could you please put datasheet and application here?)

What is the main idea for separating these three things?

 

[chuckey]

Dielectric constant ?
Frank

 

[BradtheRad]

Bombard them with acoustic waves (clicks)?

Glass will return a distinct echo.

Paper and soft plastic are less likely to send back distinct echoes.
Hard plastic, however, may easily be confused with glass.

 

[albert22]

I think that is very difficult to apply a sensor without knowing more about the shape, thickness and other characteristics of the materials that you want to sort.
In recycling plants this kind of things are separated by mechanical means. And some things even by hand.
For example some plastics float in water while glass sinks. Applying blowers and dropping the debris from a certain height separates some things.
You can search "recycling plant" on youtube to see how they do it.

 

[tpetar]

Can you describe separating process? All of these three materials are together joined and you need material separation, or you just need to detect materials?