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.


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.


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 the glass.

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 break it.

Text Font Face
Text Size
(for printing)

Try small fires first - you probably won't need a huge one in a JUCA. (If you do need a huge fire, your ductwork or cold air supply is probably insufficient). Keep the metal panel in place until you are used to the operation of your unit.

The JUCA Home Page is at: juca