Re:Electrical Tape IS IR PROOF?

[Gary Beasley <beasleyglb@xxxxxxxxxxxxxx>]

>Date: Fri, 14 Jan 2000 03:39:15 EST
>From: "Rolland Elliott" <rolland_elliott@xxxxxxxxxxx>
>Subject: Re: Electrical Tape IS IR PROOF!
>
><<<Actually many brands of electrical tape [are] transparent to infrared. I 
>built an infrared meter once and used a piece of black electrical tape as 
>the visible light blocking filter.
>This is because of using dyes instead of carbon black to make the tape
>black..... One way to check would be with an IR sensitive
>ccd camera and see how dark the tape looks with light behind it.>>>
>
>I have two kinds of black electrical tape at home
>1) Generic Black Elec. Tape that says UL Listed on the inside of the core.
>2) Scotch Super 33+ Vinyl Electrical Tape
>
>I put both kinds of tape infront of a homemade IR JVC camcorder.  The 
>generic Black electrical tape leaked a very little amount of IR light, but 
>two layers of the tape effectively blocked out all IR light
>
>One layer of Scotch Super 33+ tape blocked out all the IR light.
>
>The camcorder was pointed at a 200 Watt bulb during this test.
>
>I should note that this camcorder can easily see through a 87A, 87B, 87C and 
>87 visually opaque gels. Lastly, while I'm not an electrician, I do buy 
>electrical tape often, and these two types of tape are quite common in many 
>hardware stores I visit. They are probably the most common type of 
>electrical tape used.
>
>As one can see your own proposed testing method proves that your above 
>statement is incorrect. Maybe you should use some 87C gel over that 
>lightmeter. I don't think it's doing what it's supposed to.
>
>Other people on this list have claimed that black garbage bags leak IR 
>light.  This is NOT TRUE! Some bags do and others don't, it depends on the 
>manufacturer. I've yet to come across a bag that looks like it's made out of 
>clear plastic when looking at it through an IR camcorder.
>- -Rolland
Two brands eh? One did leak and thats enough to be leery of any certainty
of IR blocking.  BTW a dark colored bedsheet wouldn't look like clear
plastic either with a light behind it, but I wouldn't use it to cover my
darkroom window :-) .
The point is not that it looks like glass but the fact that the IR gets
through at all! If you are going to be blocking IR might as well be sure
what you use is 100% effective and reliable. 
BTW did the camera have a visually opaque filter installed for the test?
Gary Beasley
http://beasleyglb.home.mindspring.com/

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