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Re: Razor blades and glass

> As examples of material hardness, though, the majority indicated that glass
> was a bit *harder* than a knife blade (glass = 6-7, knife blade=5.5), which
> means the knife shouldn't scratch the glass.  One version, however, gave the
> knife a hardness of 6 and glass 5, in which case the blade could scratch the
> glass.

I sometimes use a single edge razor to scrape the glass.  I'm careful
not to let the blade chatter or get crooked and have a corner catch. 
I think the hardness is only part of the issue.  The area of the edge
of the blade is miniscule, so the pounds per square inch of pressure
is very high for even moderate force.  If you get the blade cocked so
all the force is exerted just on the point at one end of the blade, it
should easily exceed the strength of the glass.  Tempered glass would
probably explode.

Best regards,