[Cob] question for Sasha on Masonry stoves

[Mary Lou McFarland]

The book that I read about masonry stove construction stressed the 
importance of having a flue opening that could be held slightly open to 
prevent carbon monoxide (dioxide?) poisoning and also a place to clean any 
ash or buildup out of the air chambers, so how do you handle that?  Also, I 
have a kiln and fire porcelain and ceramics so maybe I can help with your 
tiles cracking.  Usually there are three causes. 1) you need to let them air 
dry longer before firing  2)  if cool down and the heating up process isn't 
slow enough then you will get a thermal shock resulting in a crack  3) the 
tile isn't properly supported or"proped" during firing.  Acurved tile can be 
supported with a piece of the same material that is made of, so the 
shrinkage will be the same.  Here we use this cottony like stuff that can 
withstand the temperatures and we just order from ceramic/ hobby supply 
companies.  If your tile is to be flat and you want it to stay that way then 
scratch a couple of grooves across the back and fire it on a thin bed of 
silica sand. The sand acts like little ball bearings and lets the piece move 
to accomodate the shrinkage, otherwise it will warp and then crack.  Hope 
that helps you out a little.

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