new videos
hot off the press!  
    more about rocket
mass heaters here.

more videos from
the PDC here.
  • Post Reply Bookmark Topic Watch Topic
  • New Topic

outdoor cob oven form on 'fire'  RSS feed

 
karen krakowski
Posts: 2
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
We made pizza in our oven this last Thursday and today is Monday, The external oven is internally still cooking. Not really sure how to explain, but the walls on top are hot to touch, smoke is coming out of small cracks and some areas are squishy. How do we put out the 'heat/fire' without destroying the oven.
 
Glenn Herbert
gardener
Posts: 2180
Location: Upstate NY, zone 5
74
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
We need more information on how your cob oven is built. Did you use a lot of straw? Did you build in layers isolating the straw from the inside few inches? What layers of what composition did you use in the dome?
 
Gilbert Fritz
Posts: 1300
Location: Denver, CO
22
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
I know nothing about cob, and not much about fire, but I'm curious; this sounds strange. Could it be a straw fire rather like one of those underground peat fires?
 
karen krakowski
Posts: 2
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
The 'fire' was in the insulation layer. That layer was at least 4 inches. We are thinking that the ratio of clay,sand and (we used wood chips) was off, causing our problem. We have removed the insulated layer and will redo using spent grain and wood shaving instead of wood chips. Really appreciate the reply back and will let you know what happens.
 
Glenn Herbert
gardener
Posts: 2180
Location: Upstate NY, zone 5
74
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
If you use any form of organic material in the inner part of the insulation layer, you risk it getting too hot and combusting. A thicker thermal mass layer would reduce the effect somewhat, but the best solution  might be to use perlite as the insulating ingredient for the first inch or so of the insulating layer.

Alternately, you could let the organic material burn out, as long as it isn't required for structural strength, and have a clay layer with lots of micro air pockets which would be good insulators.
 
Are you okay? You look a little big. Maybe this tiny ad will help:
2017 Rocket Mass Heater Workshop Jamboree - 15 workshops in one event
https://permies.com/wiki/63312/permaculture-projects/Rocket-Mass-Heater-Workshop-Jamboree
  • Post Reply Bookmark Topic Watch Topic
  • New Topic
Boost this thread!