Double glazed burn chamber window?

[Vortex]

That's interesting Matt, my window never soots up, I guess my stove is cleaner burning
The oven dish lids I use as my stove windows are not as good at taking the heat as proper stove glass. I just had to replace one yesterday after a log fell against it at the hottest part of the burn, directing the cold air coming in the primary air vent straight onto the hot glass. It had lasted a year, I have a few spares I've picked up in the charity shops for pennies and it only takes about 3 minutes to change so no hassle really. I would like to have the whole door as a window, not just a circle in the middle so I might have to buy myself a piece of stove glass soon, are there different grades or thicknesses?

[mpinick]

I did a double window in a 4" J stove. I have the info on in my post of the stove. Thanks mpinick.

[matthewwalker]

Vortex, I didn't mean to imply that in the flame was the only way to keep it clean. Another way, and the most common in cooler burning wood stoves, is just to not let the smoke path near the window at all. They usually accomplish this by having incoming air "wash" the window so no soot can get to it. I imagine that's what you've got going there, with the gasses heading up and towards the back of the fire box, and your primary air inlet pushing them away from the glass.

And yeah, I read a while ago that you were using Pyrex with good success. I tried about a half dozen Pyrex plates in various rockets. On the door they will last a few burns since they are well away from the hottest spots, but on a rocket you don't really see anything from behind the feed. They definitely don't last as you get closer to the burn in a rocket, and the scariest thing for me is that they tend to explode rather than crack politely. I had glowing red shards of Pyrex all over the place on one occasion and decided to not do that again.

I haven't found different thicknesses, but then again, I haven't looked. As for grades, well, again, I've only experimented with one brand, which is Schott/Robax. I have put this stuff through as much abuse as I could throw at it with super hot burns in an 8" batch stuffed with hardwood. No problem, and when it's going like that you can't get withing a few feet of that window. It's just crazy how much heat they will throw out.

[Vortex]

I'm using the oven casserole dish lids, they take a lot more heat than the plates, I've never had one explode but the noise of them cracking is so loud its quite scary. Having the primary air feed just below obviously helps keep mine clean but it's also the high temperature of the burn itself, if I try and do a small burn with less than a half filled firebox then the glass starts to get smoked. On a full burn of hardwoods you couldn't hold your hand 2 feet in fornt of my stove glass for more than a few seconds without getting burnt. I just ordered an infrared thermometer and I'm really looking forward to seeing what kind of temps I'm getting in there on a good run.

Pyrex has a max temp of around 500*C / 932*F and Robax of 760*C / 1400*F

Robax technical specifications
Pyrex technical specifications

Schott's Nextrema is guaranteed up to 950*C / 1742*F