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rocket stoves

heating clay as cast??

Posts: 11

posted 11 years ago

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I see everywhere it seems no matter the use about letting clay air dry slow then heat slow etc...

I can't do that very well with the freezing weather we been having and getting impatient to build!
Anyone just fired up a heat stack and start molding wet clay around it?
I'm thinking a 6" pipe heated with about 2" wet clay around it should cook the moisture from the inside on out, then build up another 2" and fire more, etc..
I will probably try this as a 50lb bag of clay was only $10 and if it don't work out well then I can just bust it back up and use it with fresh clay if needed.

Just curios if any one has tried to heat dry wet clay and what the results were?

I do plan to add a few stress breaks or sections. Probably just use wet paper or cardboard as needed and let it just burn out.

Mikael Long

Posts: 54

posted 11 years ago

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Hi Den

I did something like that. While the drum that sits on top of the stack was heating up I put mud/clay on it. Even with it steaming I could get it to stick but it was not easy and talk about water vapor release. At one point it was a tropical rain forest in the small space I was working. It was about 50F outside so not freezing but still cold to be working with wet clay. Starting and keeping a fire in a wet RMH is hard and requires constant attention and may not run if its too cold. Use a torch or heat gun to get it going first. I also did multiple coats on the whole RMH which took about two weeks start to finish I could run it in between to stay warm it just looked well unfinished. I looks nice now minus some small cracks which I will fix next fall or this spring. I probably will redo the whole thing and go for a larger unit. This was my first attempt and I want to pull it apart and make change to get even more from less.

Good luck
Mikael69

https://www.youtube.com/watch?v=I6voGcuedxY

trying to post youtube link not sure if that is right but it is a video of my unit in action.

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Den Stou

Posts: 11

posted 11 years ago

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My experiments did not work out yet.
I made about a 3" tall rings about 2" thick with an ID of 6", and let them air dry in good warm air, but not to hot, over the wood burner. They just cracked all to pieces and crumbled by hand. I did not bother trying to fire them after drying as they were not worth messing with. I'll just bust them up and mix in with a new batch.

Around here we should not have to worry about freezing much now so I'll cast some stuff and let it sit out to air dry slow.

thomas rubino

master rocket scientist

Posts: 6869

Location: latitude 47 N.W. montana zone 6A

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posted 11 years ago

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Hi Den; You only mention clay... are you mixing sand in with it ? cob is mostly sand with clay to bind it together. Clay alone will not hold up. I did a similar thing as mikael, adding cob to the 55 gal barrel while it was running. I found that it will work but 3 months later i am having cracking issues with the cob on the barrel. It is almost spring here in montana, your spring can't be to far away. Get a copy of ianto evans book rocket mass heaters ,for info on building a rmh and a book on cob building could help you understand mixing cob. There is a forum here at permies all about cob , there are some very smart people there. Read up, collect parts and before you know it you will have a RMH and it will be to hot to fire it off! good luck Tom

For all your Montana Masonry Heater parts (also known as) Rocket Mass heater parts.
Visit me at
dragontechrmh.com Once you go brick you will never go back!

bob golding

Posts: 48

posted 11 years ago

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Mikael Long wrote:Hi Den

I did something like that. While the drum that sits on top of the stack was heating up I put mud/clay on it. Even with it steaming I could get it to stick but it was not easy and talk about water vapor release. At one point it was a tropical rain forest in the small space I was working. It was about 50F outside so not freezing but still cold to be working with wet clay. Starting and keeping a fire in a wet RMH is hard and requires constant attention and may not run if its too cold. Use a torch or heat gun to get it going first. I also did multiple coats on the whole RMH which took about two weeks start to finish I could run it in between to stay warm it just looked well unfinished. I looks nice now minus some small cracks which I will fix next fall or this spring. I probably will redo the whole thing and go for a larger unit. This was my first attempt and I want to pull it apart and make change to get even more from less.

Good luck
Mikael69

https://www.youtube.com/watch?v=I6voGcuedxY

trying to post youtube link not sure if that is right but it is a video of my unit in action.

hi, i am a newby so may / does not know what i am talking about yet, so please forgive me if i have this wrong. from what i have read the outer barrel acts as a cold area for the hot gases to descend into as they leave the riser. this needs the outer barrel to be relatively cool i thought for this process to work properly. covering the barrel with clay will hinder this process somewhat i would have thought.

Thomas Rumbach

Posts: 3

Location: United States

posted 11 years ago

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I think you still need air drying for 24 hr. Then then add more but heat on wet clay makes steam boom
But I have sum copper cuttings and I was thinking of adding them or steel cuttings, nice size chips

I have a knack for fixing things like this ... um ... sorry ... here is a concilitory tiny ad:

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