30" cast dome design

[david s]

I did say 700 ml (not grams) for every 10 litres dry render mix. The fibres are pretty light.
I also said keep covered for a week to damp cure. Depending on how thick you make your render layer it will still require drying. Even at 10 mm that will take more than a few days. Forget pizza for now, I know it’s hard, but you wouldn’t jump in a brand new car and yes it’s top speed on delivery. Be content with roasting some chickens or pork roasts for a few firings before going for pizza temperature.

[sergetania]

Are we talking about AR fiberglass fibers? The stuff in the picture below? That's what I got and I was surprised of how heavy they were for the volume.

Googled 1 liter of dry concrete = 5.3 lbs (LOTS of stuff on the Internets!). So 80 lbs need about 1 liter of fibers. I think one pound is about right for a 80-lb of dry stucco. Thanks!

Will wait, roast something else at 400-500F. Not the worst hobby I had in terms of waiting. Homebrewing was the hardest! I can do it! Chicken wings will sooth the pain! Thanks, David!!!

[david s]

Those fibres look like mine and I’d say 1 lb/80lb dry render sounds about right. The roast chicken should go well with the .

[sergetania]

With homebrew? Stopped homebrewing,too hard (for my back). I did pretty good for a few years though.

I am watching the curing fire #5, reaching 600F. Pretty cool. It seems above 500F the oven just takes care of burning anything without smoking much. The top of the front arch is pretty black though, lots of smoke was coming out of the oven opening.

[david s]

Carbon begins to burn off at around 600F (300C) so the top of the dome should be clear. I often use this indicator for my oven to stop adding wood and begin roasting or baking. For my oven this takes one hour to reach this temperature and saves time and fuel. All new ovens are smoky, the smoke escaping out the front will lessen as the oven dries more.

[sergetania]

On my last curing fire, followed David's advice and roasted some fish. Turned out quite nice, especially for the first time! Need to tailor my cookware to the oven. 30" is somewhat of a tight fit but it will work.

[sergetania]

Need help, PLEASE, rather urgent!

I am planning to render the dome today. I thought I would ask before making a mess. The picture of the side of the dome is below. The base and the perlite dome with a hairline crack between them. The question - how do I stucco that? I need 10-15 mm layer of stucco. Do I start at the bottom of the base or the dome? Will the stucco stick with nothing below (I will be using a bonding adhesive, the one you add to the mix instead of a part of the water)? Sorry, first time doing this. THANKS for the help!

[david s]

A smal gap or crack like that is nothing to worry about, the render wil bridge it ok. Is the perlcrete layer thoroughly dry? It will contain wat more water than you think and how it appears. It is prudent to eliminate as much of this water as you can before rendering over it because steam expansion pressure can easily crack the outer shell. Do the 7 fires in 7 days getting progressively bigger before rendering over it. This will be enough to drive water out of the internal dome as well as the vermicrete layer. If unsure, throw some plastic over the dome during firing to make sure there’s no condensation on the underside.
Unfortunately this leaves a very dry substrate which will want to suck the moisture from your render. To counter this effect wrap the whole oven in clingwrap once the render is done. This will hold the moisture in that layer well. Do not uncover it for a week.

[sergetania]

David, I did the seven fires. Last time the temp of the dome reached 850F. I roasted some fish and it tasted good! Now if the rains start the perlite will be just sucking water so I want to go ahead with render and then dry it gently again (I do have a breather tube through perlite).

Also,not worried about the crack. What I was trying to find out how I put the stucco over the bottom of the oven. I guess I will bridge the base and the dome and hope the stucco sticks even with nothing to hold it below the base. I will just round the bottom edge, right?

[david s]

All good then. I’d be dampening the edge of the concrete slab before rendering then. Start as usual from the bottom up.You should be fine, but when you’ve finished use a wet sponge to go over the whole surface. It will remove any tooling marks. Covering it then is important as holding the moisture in the outer layer for a week does increase its strength significantly.

[sergetania]

Will do all that, David! Thank you! I made a float from polystyrene foam with the same radius as the dome. If using that with water doesn't smooth out the surface I will use a sponge. It's just scary to do this for the first time though I have watched a bunch of videos.

[sergetania]

You should be fine

No, David, it will take a few days before I feel fine again! My computer hands will feel this for a while! It looks easy in YouTube videos! It's HARD work!

Again, lots of respect for people who do this for living! I think if I do it again the result will be better. By the time I was done with it the render on the bottom got too hard to smooth out all gouges. I guess it will give the oven a character. I will feel bad about it but I really don't want to do another layer. I hope I am done. Covered with plastic wrap and plastic cover, it is curing. It is what it is...

Oh, btw, it is hairy in a few spots because of the glass fibers. It's especially bad around the facade. I need to shave it somehow

[david s]

Use sandpaper to knock back any fibres sticking out.

[sergetania]

Great! Assuming after 7 days of wet curing will have passed, right? I think so. Thank you!

[sergetania]

7 days have passed and here it is. If I ever do stucco again it will be smoother. At least this one seems to be strong. I will cover it with flashing sealant and hope it will make it look better.