I went to start a fire this evening and found that the whole top of my burn tunnel had fallen off.
![Confused :?](./images/smilies/icon_e_confused.gif)
![Image](http://i1338.photobucket.com/albums/o691/mannytheseacow/RMH/chunk_zps3c74d64c.jpg)
![Image](http://i1338.photobucket.com/albums/o691/mannytheseacow/RMH/chunk2_zpsae988626.jpg)
I know these things are delicate but I've never lost this much before. It's really a hard place to patch, too, because this stuff doesn't like to stick to dry core.
Thinking back to casting it, this spot had a lot of water glass, refractory mortar and refractory cement.... I wonder if all the additives aren't as dependable as the basic clay/perlite mix?