On Friday 18 February 2005 14:53, Pat Naughtin wrote:
> This area looks to be screaming out for the standards writers to come to
> their rescue by writing a uniform standard using an SI unit such as a
> pascal (newton per square metre) in one or several of its many forms from
> millipascal to megapascal.
I think what's happening is they're conflating several quantities and calling
them "hardness". There are the moduli, such as Young's modulus, which are the
ratio of stress to strain, that is, the amount of pressure needed to deform
it elastically by a certain amount. Then there's the elastic limit, which is
the stress beyond which it is permanently deformed.
I henna my hair. Lawsone binds with keratin, filling microscopic cracks and
making it harder, but it makes the mass of hair softer. How do you measure
that?
My father had a set of variously colored plastic disks about 3 cm in diameter,
each of a different hardness, held together with a ball chain passing through
the hole in the middle. I thought he was the only person who had one of
those, until I met an Israelite named David who had one too. Any idea where
to get them?
phma
--
Now I need a magnifier to find my eyeglasses!
-Les Perles de la m�decine
