The glass of a lens should be about the same Moh's hardness as quartz, 7, since it's predominately quartz. I have no idea about the hardness of coatings, but aren't they only a few molecules thick?
Bill ----- Original Message ----- From: "Aric" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Thursday, February 19, 2004 10:57 PM Subject: RE: Lens Cleaning Problem - Volatile Liquids > What is much harder than talc? Lens coatings, or graphite? Obviously, lens > coatings are much harder than either. I stated I had no idea how to > quantify the difference. I referenced Moh's hardness scale, which is a > rather coarse measure of hardness. On Moh's scale, graphite and talc are > given the same hardness: 1. The traditional way to determine where on the > Moh's scale a material lies, is to attempt to scratch it with a > representative mineral for each hardness number. I don't intend to > volunteer any of my lenses! :) > > If SMC coatings are harder than glass, then I would expect even a vigorous > cleaning with graphite would do nothing more than yield a very clean lens. > > Aric > > -----Original Message----- > From: Bob Blakely [mailto:[EMAIL PROTECTED] > Sent: Thursday, February 19, 2004 10:37 PM > To: [EMAIL PROTECTED] > Subject: Re: Lens Cleaning Problem - Volatile Liquids > > > It is much harder than talc. Think about it. > > From: "Rothman, Aric" <[EMAIL PROTECTED]> > > > > Interestingly, carbon (graphite) is both the softest (tying with talc), > and hardest (diamond) mineral, per Moh's > > hardness scale. Depends on its molecular structure. > > > > I have no idea how the typical lens coating material compares in hardness, > quantitatively speaking. > > > > > From: graywolf [mailto:[EMAIL PROTECTED] > > > > > > Well, carbon is the hardest stuff known, so of course it has > > > an abrasive effect. > > > But the stuff used for this is super, super fine so it > > > polishes rather than > > > scratches. I would not recomment daily use though. > > > > >
