your own polariscope

Make your own polariscope, download free electrical scheme and designs at:

http://www.astorimarco.com/pagine2li...lariscope.html

Have a nice week-end

Marco

Glass artists (especially kiln-formed) often use two pieces of pieces
of polarized film to detect stress in glass. Is this anything like
that?

- Paul

_________________
Get your daily dose of
glass knowledge at
http://www.glassfacts.info

On Sat, 05 Feb 2005 15:52:44 -0800, in ¸õ wrote:

Glass artists (especially kiln-formed) often use two pieces of pieces
of polarized film to detect stress in glass. Is this anything like
that?

- Paul

_________________
Get your daily dose of
glass knowledge at
http://www.glassfacts.info


Yes. Though the plans shown are more along the lines of the designs found in
gemological polariscops, which may be smaller and look a bit fancier, and certainly have
higher price tags than what would be suggested by two pieces of crossed polaroid...

the basic principal is the same. Two polaroid filters (which should be linear or plane
polarizers, not the sometimes seen circular polarizers such as in some types of camera
filters. Plane polarizers have one consistant direction of polarization. Anyway, two
of them, with the polarizing directions at 90 degrees to each other, block normal light
from passing through both. Strained materials, be they glass or gemstone, "twist" the
polarization directions of light passing through the materials, so light that passes
through one filter, and then the glass or gem, may not be polarized at 90 degrees to the
second filter any more, so it then passes through the filter. The result is that gems
or glass seen with this arrangement may show areas where light appears bright, or where
certain colors appear. Gem materials, due to their crystaline structure, may show, for
some types, quite specific patterns and behaviors which aid in their identification.

Peter