What is GLASS?
Glass is the portion of the light bulb where light energy escapes.
Glass on common household bulbs is typically colored a soft-white coating.
Otherwise, incandescent bulb glass is usually clear unless noted elsewhere.
Glass for most Incandescent bulbs is common soft glass, but halogen bulbs have their glass near the filament so glass becomes much hotter and to prevent soft glass from melting; special high temperature quartz (fused silica) glass is used.
On quartz glass bulbs you must wipe all fingerprints and contaminants from glass before using or glass upon heating and over time will chemically react (divitrification) becoming foggy and brittle (bulb could explode).
Letters which precede number are industry codes for glass shape.
Number that follow indicate glass size diameter in eighth inches unless millimeters are specifically indicated.
For example; if the proceeding number is 12, then 12/8th inches would indicate glass portion to be 1.5 inches in diameter.
Number 3.25 would indicate glass is 3.25/8 th or 13/32 th (0.41) inch diameter.
Of course if the number was 40mm, then the glass diameter would be 40 millimeters.
Glass is also an insulator.
reference for this page: GLASS
references to this page: /C, /CL, /DTUBE, /FR, /HF, /IF, /LF, /LONG, /SB, /SHORT, /TC, /UVS, BULB DARKENING, DICHROIC MIRROR, DIVITRIFICATION, END BLACKENING, ETCH, FILAMENT, FLUORESCENT LAMP, GLOW LAMP, HALOGEN BULB, INCANDESCENT BULB, INSULATOR, LENS, LIGHT BULBS, NEODYMIUM, PAR LAMP, PHOSPHOR, QUARTZ GLASS, RE-RATE, REFLECTOR LAMP, SHROUD