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.
