NOTES CONCERNING THE USE OF PRISM PLATES.
VERTICAL PLATES.
1. Where plates are exposed to the weather,
the area of one plate should not exceed fifteen (15) square feet; where
sash opening is larger than this, divide it by means of iron sash bars,
making two or more plates.
2. For dimensions, calculate each prism lens an
even four (4) inches, allowing one-half (½) inch all around for
brass or iron border. When brass border is used add one eighth
(1/8) inch more for plates of dimensions less than
forty-eight (48) inches (the 1/8-inch allowance is not
made where iron border is used); for plates greater than forty-eight
(48) inches no extra allowance is to be made.
3. Sash should be rabbeted with reference to
admitting brass or iron border of prism plates, the rabbet being one-half
inch deep where possible. See detail sheets of sash.
4. In special cases, bars one-half (½)
inch wide by one-quarter (¼) inch thick, may be glazed into
prism plates to receive stiffening bars. See detail sheets of canopies.
5. Where "Filler Prisms" are required their
location should be clearly designated. These fillers are made in the
following widths -- ½ inch, ¾ inch, 1 inch, 1¼ inch,
1½ inch, 1¾ inch. By combining these with the prism lenses
any with and height of plate can be made. Fillers are made for vertical
plates only. See filler diagram.
No fillers are made for canopy plates.
6. Iron borders of prism plates are
½×¼ inch.
7. Where prism plates have curved outlines, iron
borders must be used.
8. The sight opening of sash should clear prisms
one-sixteenth (1/16) inch all around. See detail sheets
of sash.
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