wrote in message
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On Mon, 29 Oct 2007 12:45:18 -0400, "Eisboch" wrote:



Umm. I think the scratch coating is included on all plastic eyeglass
lenses at no charge these days. I haven't paid extra for it in over 20
years.



Well, they shouldn't charge for it. You can't make a relatively soft
material harder by putting a very thin (few hundred angstrom) hard coating
on it. It's like trying to make foam rubber hard by applying a thin coat
of enamel paint.

Some of the newer plastics are, by virtue of their chemistry, harder than
others and therefore more "scratch resistant".

Eisboch