Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!tut.cis.ohio-state.edu!ucbvax!ernie.Berkeley.EDU!jwl
From: jwl@ernie.Berkeley.EDU (James Wilbur Lewis)
Newsgroups: comp.graphics
Subject: Re: Steel colors
Message-ID: <29298@ucbvax.BERKELEY.EDU>
Date: 24 May 89 05:02:46 GMT
References: <31@oink.UUCP>
Sender: usenet@ucbvax.BERKELEY.EDU
Reply-To: jwl@ernie.Berkeley.EDU.UUCP (James Wilbur Lewis)
Organization: University of California, Berkeley
Lines: 16

In article <31@oink.UUCP> jep@oink.UUCP (James E. Prior) writes:
>I've noticed that when I look closely at reasonably clean bare steel in good
>sunlight that it appears to have a very fine grain of colors.  
>
>What is this due to?

Probably a diffraction-grating type effect due to scratches, roughness, or
possibly crystalline structure at the surface.

I've heard that a similar phenomenon is responsible for iridescent blue
coloring of certain kinds of birds...there's not actually a pigment of
that color, but the fine structure of the feathers makes the reflected light
look bluish.

-- Jim Lewis
   U.C. Berkeley