Re: Large cities at time of contact Re: diseases and immunity
Thu, 04 Jul 1996 11:43:46 -0700

OK, I stopped to examine the process for manufacturing these modern glass knives.
The glass used in these is a variation of the inexpensive soda lime glass. The
glass is chemically tempered to bring the structure to within 1% of the natural
crystaline structure. (Not seen in any volcanic glass of which I am aware, but
possible). This produces a glass which is 5x harder than ordinary soda-lime glass.
The glass is sold in sheets,(drastically different in form from either cores or
blanks) and the disposable blades are made as needed by scoring the glass on both
sides to control the fracture (not the same as the percussion and pressure flaking
techniques used on vocanic glass. Although superior to standard soda lime glass,
the edges of these blades are still brittle and lose their edge quickly.
(inexpensive on-disposable blades are made from sapphire).

Although the silica content between this manufactured glass and volcanic glass is
similar, the form and structure of the glasses are significantly different.
Because of these differences, the fracturing process used on manufactured glass is
different than that used on volcanic glass. The accuracy of the first process is
much greater than that of the second. And, while the manufactured glass is
superior to the volcanic glass, it still suffers the limitations common to glass
in general.