"Casserole" doors - $8 for 8" diameter 1560F rated glass

So, I like the idea of the casserole doors but while standard pyrex should be able to handle 900F,  it's boro silicate glass still prone to cracking from thermal shock.

I just found out that Corning/Pyrex has recently re-introduced a line of Pyroceram cookware called "Visions", than is rated to 1,560F and better able to handle thermal shock.

https://en.wikipedia.org/wiki/Visions_(cookware)

There's a  8.25"  diameter lid for $8  (+$6 shipping).  It's a smokey color, and round  vs oblong of a true casserole lid.  Cheaper than Neo-ceram!

https://www.pyrexhome.com/product/glass-lid-2.35-liter-dutch-oven-pot-or-2.5-liter-saucepan-0

Hey Daniel;
These might do ok with a 1500F rating.
I would buy an extra one to have on hand in case the original does not last.
Nothing worse than your batch box door breaking while a load is burning!

My temporary plug / doors are made with metal and Morgan super wool insulation.
They can have a window or not.
They will not break.

I actually ordered 3 to have extras, and not have to pay shipping again if one breaks.    These are for prototype ovens.   It's not obvious to me how to build a metal door with a window, and also  NeoCeram seems to go for ~$50 for a 6"x4" piece.   So I'm prototyping with a casserole plunge-door to avoid the cost and skill issues for now.

I suppose finding used / broken woodstoves and stealing their doors would also solve both problems for me, but I don't know a source for that.

So.... I found an old thread here on Permies where others have tried Visions pyroceram lids in the past, and still gotten some shattering issues.   I'm still going to try using the lids I got, but with a slight modification.  I'm going to cover the rim with high-temp silicone caulk.

Breaking risk goes up with scratches and nicks in the glass.  They concentrate stresses and lead to early failure.  And it's easy to get scratches when your door mates against  a refractory mix stove and also possibly putting the lid down on rough surfaces.

So, maybe the failures seen were due to a combo of scratches and lots of thermal cycles.  If true, then coating the mating surface in high-temp silicone to prevent scratching should increase the glass lifetime.  Also, if the caulk is applied thick enough, it's also a buffer against thermal shock when you put the lid down somewhere.

I'll post if it fails massively.....

I am assuming you want to use the bowl on a batch box?
The attempts I have seen sort of lay the dish at an angle so it is resting in place but, I think this exposes the bowl to a lot more heat that a vertical door?
High temp silicone is rated to around 500f but it goes gooey and soft before that, more like 400f working temp.
Perhaps a bowl  might work on a small 4” batch box but personally I would look for a cast iron baking tray or something that can be installed vertically  preferably on hinges.

Yeah, the temp rating is a concern.  I was hoping that by applying it just to the rim, which will be nestled in insulated refractory, it won't be exposed to the full heat, but it's probably wishful thinking as the glass itself will conduct heat to the rim region.  

I've seen higher temp coatings, but they tend to get expensive, and this was supposed to for cheap prototyping.....  I'll try to arrange the primary air to wash over the door to keep it cooler, and shield the silicone from direct radiation and air as mentioned above.  We'll see if it fails spectacularly or not.