Q: We have been heating our house for the past 27 years with a firewood stove (about 23 years with a Fisher
airtight). I really like all the information on your site about new versus old stoves, less smoke, etc. Here is my
question..... I`m a belt & suspenders kind of guy. EVERYTHING I`ve seen new has a viewport to look at the
flames, but I WANT SOLID METAL ALL OVER. Yeah, I know most people want to SEE a fire, but I don`t feel
comfortable leaving a stove unattended with a piece of glass ANYWHERE on it. Can you sell me a new, improved
stove I can trust? Thanks in advance for whatever insight you can convey.
Sincerely, Jim
 Hi Jim,
Viewing windows don't exist just to brighten the room with a cheery glow of flames; they provide a level of
precision woodstove operation that wasn't possible with the old, solid-metal models. For example, viewing windows
allow you to see at a glance whether the load might need to be adjusted, and when it is time to refuel. They also
provide an easy means for you to ensure that the fire isn't smoldering, eliminating one of the biggest causes of
chimney fires.
Many years ago, I used to feel the same way you do about woodstove viewing windows. The tempered glass and
Pyrex materials used in those days not only sooted right up, but were prone to breakage. Then, about 20 years
ago, I saw a demonstration of a then-new product of NASA research: a
transparent ceramic material that was
much stronger than glass, didn't shatter when broken by impact, and couldn't be broken by thermal shock.
The demonstration was pretty dramatic; a pane of ceramic "glass" was suspended by chains attached to the four
corners and heated from below with a welding torch until it was GLOWING WHITE HOT. It didn't break, to the
amazement of the crowd. But the demonstration wasn't over: when a cup of ice water was poured on the top of the
glowing-hot pane and it still didn't break, I was sold.
And so was the rest of the hearth product industry: in today's wood stoves, the
viewing windows are ceramic, not glass.
The only potentially dangerous situation I can think of that might pertain to woodstove viewing windows would be
a case where the window shattered somehow while the stove was burning unattended, leaving a large enough hole
for burning wood or hot coals to tumble out with enough force to travel beyond the non-combustible hearth and
ignite surrounding combustibles. This would be an unlikely scenario in any case, but can't happen at all with
ceramic glass, for three reasons: (1) the material can easily withstand temperatures that would burn holes in your
Fisher (2) it would take an impact far greater than a piece of wood falling against it to break it, and
(3) when it
does break, it doesn't shatter. In fact, the material has proved to be 100% safe for woodstove applications, which
is why it is used by virtually every woodstove manufacturer today.
We have been selling woodstoves with ceramic viewing windows for nearly three decades now, and we've never
seen or even heard of a single case where a ceramic window caused any kind of hazardous situation. Breakage is
extremely rare, and generally only occurs when someone has added a fresh load of fuel, and,
not considering the multiplication of force created by a second-class lever, attempts to muscle
the door closed against a too-large piece of wood that protrudes beyond the door opening. Even when this happens, the ceramic simply cracks, and
the mounting brackets ensure that the pieces remain in place, not creating a large enough opening for even the
smallest burning ember to escape. We've had customers continue to use their woodstoves for months with
cracked viewing windows.
You asked if we could sell you a new, improved woodstove you can trust, and the answer is a resounding YES. All
of the models shown on our wood stove main page have proved to be extremely safe and reliable, and also offer
the many advantages of a stay-clear ceramic viewing window.
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Re: your item on viewing windows, it fails to mention the most important reason for having one - that is the
increased radiant heat (high level radiation) as against the low level black heat radiated by the stove body.
Regards
John Connor
UK Chimney Sweep
Hi John,
Thanks for the input! It is true that the ceramic glass used in today's woodstoves is more heat transfer-efficient
than steel, cast iron, stone or firebrick, so the presence of a viewing window increases the speed and rate of heat
transfer into the room.
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