Tempered Heat-Resistant Glass
This is used by nearly all glass firescreen manufacturers. It easily
passes the brutal safety testing to Underwriters Laboratory standards
(UL 127, UL 737, UL 1482). It has a good combination of high
strength and heat-resistance. Since it is glass, it can be broken.
If it breaks, it breaks quite loudly, in many small pieces. Since
the glass is likely to fall out if broken, it is very important to
keep the metal protective panel in place when the unit is unattended
so that there is no chance that sparks from the fire could get out.
The sturdy JUCA mesh screen against the outside of the glass would
keep the pieces in.
CAUSES OF BREAKAGE
Glass is somewhat unpredictable material. That is why glass
manufacturers do not warranty their tempered glass. Be very careful
not to chip the edges. The tempering process puts internal stresses
in the glass (intentionally) that produces its strength and
heat-resistance. After it is tempered, a small chip could localize
these stresses and immediately weaken or break the glass.
When you install the glass (being careful not to chip it) install
it relatively loosely. This allows the glass and steel door to expand
and contract naturally with the temperature changes without putting
the glass in a bind. The mesh screen spring-loads the glass
loosely against the frame.
THE MOST LIKELY CAUSE OF GLASS BREAKAGE IS RELATED TO IMPROPER
USE OF THE UNIT
Tempered glass "ages" and loses its temper over time. At the
normal JUCA design glass temperature of 370°F, the glass will still
be well tempered hundreds of years from now. Even at 500°F it
will last well over 50 years. But if the glass gets to 950°F,
just 20 seconds will age it as much as 80 years at 500°F.
If you build an extremely intense fire, even for a few minutes,
you might cause such rapid aging. Similarly, a log burning against
the glass or jets of flame that continuously hit the glass will
do it. Under these conditions, you could shorten the glass panel
lifetime from 50 years to mere minutes. THE GLASS COULD THEN BE
INTERNALLY WEAKENED AND MIGHT BREAK DURING A LATER, MUCH SMALLER FIRE.
Reasonable precautions can prevent this. Proper stacking of the
wood and avoidance of resinous or glue-impregnated materials such
as Masonite, plywood, fenceposts, rail-road ties, etc. will help.
So will regular usage of the protective metal panel in your JUCA.
Make sure jets of fire don't come out the ends of the logs to hit
If flame occasionally touches the glass, that causes no problem.
Continuous overheating of the glass is what might cause it to break.
If the heated glass is splashed with water or snow, that also could