From: ornitz@kodak.kodak.com (Barry Ornitz)
Subject: Re: can a paint be made to absorb microwaves?
Followup-To: sci.electronics
Summary: When will they ever learn?
Keywords: radar, microwaves, stealth, absorbers, dielectrics
Organization: Eastman Kodak Company, Eastman Chemical Company Research Labs
Distribution: usa
Date: Fri, 14 Aug 92 22:55:00 GMT

In article <1992Aug14.182851.11261@unixland.natick.ma.us> 
lobsang@unixland.natick.ma.us (Michael Levin) writes:
>    If there is a better newsgroup for this question, please let me
>know. I am wondering if it is possible to make up a paint-like
>substance (i.e., something that can be painted onto metal or some
>other coating in a thin layer, and stay there) which would absorb most
>microwave radiation directed at it. 

Looking for a paint to use on your car to make it stealth, right?

The quick practical answer to your question is NO.

Paint can certainly be made to absorb microwaves.  Ordinary paint does so.
Can it absorb all of the incident microwaves?  Not very likely...

The problem is that you asked for "thin".  The best absorbers are generally
at least a quarter wavelength thick.  Broadband absorbers are less efficient
than band-specific absorbers which use the wave reflected off the back surface
to be out of phase with the wave reflected from the front surface.  The
so-called stealth technology developed for the military is based mainly on
reflecting the incident microwaves away from the microwave emitter thus giving
a low radar cross section.  Very little actual use is made of absorbing paint
(except perhaps in the visible region).

It is probably not much of an effect with automobiles, but at supersonic
speeds an aircraft produces a bow wave of pressure differential ahead of the
aircraft.  This bow wave produces a dielectric discontinuity which acts as a
radar reflector.  Thus a perfectly "stealth" aircraft can still be seen on
radar.  The effect is not large so "stealth" technology is still a benefit
for reducing the effective range of a radar.

Better groups would be the sci.electronics and sci.physics groups.  Remember 
that a good sincerity check on answers you recieve is to ask anyone that says
yes to produce a manufacturer of said paint!  Lots of companies make radar
absorbing materials but none make what you are looking for.  If you need
convincing call the following companies:

	Emerson & Cuming, Inc.		Plessey Microwave Materials
	Astrolab, Inc.			Indianna General Ferrite Products
	Keene Corp. Advanced Absorber Products
	Laminaire Corp.			Duracote Corp.
	Swift Textile Metalizing	United Foam Plastics Corp.

Why not buy a radar detector or just obey the speed limits?  Or....

You could cover your car with microwave anechoic foam.  But then your wind
drag would probably keep you below the speed limits anyway!  ;-)
					Barry
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|  ___  ________  |       Dr. Barry L. Ornitz          WA4VZQ
| |  / /        | |       Eastman Kodak Company
| | / /         | |       Eastman Chemical Company Research Laboratories
| |< < K O D A K| |       Process Instrumentation Research Laboratory
| | \ \         | |       P. O. Box 1972, Building 167B
| |__\ \________| |       Kingsport, TN  37662       615/229-4904
|                 |       INTERNET:   ornitz@kodak.com
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Newsgroups: sci.engr.chem,sci.chem