Stacking tiles in bisque fire

[Michael D]

Hi, I  make small tiles in my ConeArt kiln, Cone 6.  For economic reasons I have been stacking the tiles horizontally, sometimes several of them-- with not problems for the bisque firing. They seem to be bisqueing fine. My question is: so long as the tiles are dry, and that the kiln has sufficient power, is there any reason why I shouldn't stack the tiles much higher, say 5 or 6 inches high? Especially if I leave an inch or so space around each stack?

Thanks

Michael

 

[liambesaw]

Wellllll, if your clay body is fairly "clean", it could be ok, but really you should have as much oxygen as possible touching as much of each tiles surface as possible to help burn out and convert carbonates and sulfates and organics into their gaseous form.  Otherwise you could end up with gassing off in glaze firing, bloat in glaze firing, etc.  You'll just have to test and see.

[Michael D]

I never thought of oxygen needing to flood the surfaces of the tiles.  If in the future I grooved the bottoms of the tiles this might make a big difference as it would allow much more oxygen and sulfates to come and go..... Right now it is just the texture from canvas, probably not enough. Thanks!

 

[Mark C.]

Grooved bottoms make for better cement bonding. If your clay is a light white (not dirty brown stonewares) it should be fine to stack higher. You can also bisque on sides if they do not warp.

[neilestrick]

From a firing standpoint, when you stack totally flat things like tiles, you're essentially creating one thick piece. The heat is going to take longer to penetrate, oxygen won't penetrate as easily, and water vapor will have a harder time escaping from the middle. More chance of explosions and poor burnout. So if you stack 6 tiles that are 1/4" thick, it's going to behave about like firing one 1 1/2" thick tile. Just keep that it mind. Personally, I would stack them vertically, slightly leaning so there are small air gaps between them, or lay them flat and overlapping like a domino row that has fallen. You can stack many domino rows without issue because there will be gaps for air flow.

[algebraist]

Sorry for joining the conversation late, but I am just starting up some tile production, and need to ask: Do you not worry about warping during bisque firing?  If warping is unlikely, then I love the domino and vertical ideas; otherwise I might have to go all out with individual tiles on tile setters like I will be doing for glaze firings.  Thanks in advance for your thoughts.

[neilestrick]

2 hours ago, algebraist said:

Sorry for joining the conversation late, but I am just starting up some tile production, and need to ask: Do you not worry about warping during bisque firing?  If warping is unlikely, then I love the domino and vertical ideas; otherwise I might have to go all out with individual tiles on tile setters like I will be doing for glaze firings.  Thanks in advance for your thoughts.

The clay doesn't get close enough to its melting point for warping to be an issue during bisque. If it does warp in bisque, that is likely due to clay particle orientation during the forming process, and would happen regardless of the position in which it's fired.

[algebraist]

Thanks, Neil, for the very helpful information -- greatly appreciated.