Can anyone provide input on the best way to line my vermicrete dome? What material and thickness should I use?
I see refactory in Rutland castable, Mizzou castable, and a couple others. Or is there a better material that will stay in place?
Thanks!
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Saving my exercise ball project
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Okay I did think maybe the forums got set back a time period due to an issue. That explains things!
I do think my flue is a bit small but there is enough material where I can open it up some more. I kind of like the square/rectangle look of it.
The air dryer is one like this: https://www.amazon.com/Davis-Instrum...dp/B0014TMXVA/
Might leave that in there through the weekend. As far as weight I'm not sure. I used 5cu/ft of vermiculite (maybe 10lbs?) and appx 50lbs or portland cement. So 60lbs of material dry. Wet it has to be double that. I gently lifted one side up by the tunnel and while heavy I could lift it.
The plan for now is to let it dry more and then line the inside with refractory. Still unsure if I want to do the ceramic blanket then render or just render straight over the dome. I have time to think about it. I may invest in the blanket if the liner comes out good.
This was supposed to be a cheap build but as usual its snowballing haha.
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Two inches of dry loose perlite would be minimal insulation for the dome. If you mix it with cement, even at 1:10 which is about as lean as you can go and still be workable to stick to the hemisphere, its insulation value is reduced considerably. (see attached table). The higher the temperature the greater the heat loss and as pizza temperature is pretty hot ~400C then its loss is also pretty high, especially with the oven door open. This is why a fire on the side must be maintained to hold the oven to pizza temperature. Experience has proved a minimum of 3" of vermicrete insulation or 2" of blanket is about as thin as you can go, most would prefer more.
In the building of your oven there is lots of added water, depending on size you may have added around 100 litres of water. lighting some candles will do little to drive out the water. Try around 10 kg of bbq fuel briquettes and a little kindling to keep them alight for some serious gentle heat.
Last edited by david s; 05-22-2020, 12:30 AM.
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Seems the forum was hacked and has been reset back a couple of weeks. That time relates to my joining so I have also had to to rejoin.
I like your progress since your initial post. I am just making up my entrance and I will think about a rectangular rather than circular flue. This would allow me to maximise my flue size but keep my tunnel length to a minimum. I keep reading that for this size oven you need a 6 inch flue. My memory of your original post was that your dome was 30 inch. Mine is over a 750mm gym ball.
Have you done any estimates as to the approximate weight of your build to date.
Don't have a boat dehumidifier or the like but sore reference to someone using cheap candles. Wonder about a heating mat like used in homebrew beer or a aquarium heater that are thermostat controlled.
Are you going for a skim coat only over the chicken wire or continuing on with blankets and more vermiculite.
My plan is a cm or two of homebrew two inches of perlite and then a skim mortar coat. I wonder about weight and efficiency.
I am not going for a baking oven but a relatively light and efficient pizza oven.
It has to be better than the commercially made stainless steel and wood pellet oven that started this quest. Not to mention cheaper along with the satisfaction of building ones own.
I will follow your posts with great interest.
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Saving my exercise ball project
For some reason my original post and the two replies I got have been deleted and my account gone. Had to re-register.
Thanks 7yearswait and KJB for the replies, here is what I wrote in response:
Thanks for the info! I found a lot of this out after the fact. I would have started with a homebrew layer first then the vermicrete over that with refractory cement instead of portland. But I'm this far so going to try to save the project!
& days was yesterday so I removed the plastic film from the outside and took the ball and tunnel mould out. Inside is definitely damp so I'll let it sit for a while and the air can get in there and dry it out.
I think I might get some castable refractory cement and use that to make an inner liner. Then figure out the render layer later once I get it on a base and stand.
@7yearswait - Yeah I'm in Bristol, CT about an hour from New York City. I can probably get Vitcas shipped over but might be expensive. I'll see if I can find any in the US.
@KJB - The flue in that picture is being formed inside that cardboard box, and there is a long wooden plug wrapped in plastic in the center. Slid out with some gentle tapping.
Going to let the dome sit until next week, too much going on to work on it now. The additional dry time will be good for it. I have an air dryer that you place in boats during storage to keep the moisture away. I may put that in there closed off for some time. It creates gentle heat.
Thanks again for all the help I really appreciate it! I'll do my best!!Tags: None
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