>>I'm building a universal IR receiver/transmitter and I need some plastic
>>that is dark in color, yet passes IR easily. Will ordinary red acrylic
>>work?
>>Just what is the right stuff to use?
>
>
> Most dark tinted hardware store acrylic should pass IR just fine.
>
> However, if you don't trust it, the easy test is to take an IR source
> (say, your TV remote) along to the hardware store with you, put
> it behind the acrylic in question, and look "through" the acrylic
> with a digital camera (camera phones work GREAT for this).  If
> the substance in question is truly IR transparent you'll see the
> LED just fine through it on the camera's display.
>
> An alternative is to use developed 35mm film negatives (without
> pictures, of course!)  Usually, the returned negatives from a roll
> have a couple of inches of exposed film without pictures at the
> end.  I bet a 1 hour photomat would probably give you all the
> film trimmings you can eat if you ask nicely.