making fire hearth on mobile oven

[kirshner]

Re: making fire hearth on mobile oven

thanks will do

[david s]

Re: making fire hearth on mobile oven

Read the thread on oven curing. If it were mine I'd be doing some lower temp cooking (roasting and baking) for a couple of weeks before attempting pizza temperatures.

[kirshner]

Re: making fire hearth on mobile oven

but I can still fire it up for operation 3 weeks after hearth goes down tomorrow?
will do a small fire first, then bigger one next day ,build it up before cook up

[kirshner]

Re: making fire hearth on mobile oven

thanks david
sigh of relief...
the vermaculite is 7 to 1 on base but i packed it down pretty hard,and it feels solid, plus up against strong walls,I really dont want to take it apart and start over Ha ha which i did with the dome.you may remember my first dome had lime, small river pebbles, sand and refrack concrete, well a friend is using it and it hasnt exploded yet,but glad I made another anyway.
there are so many variables and things to learn with this thing
cheers

[david s]

Re: making fire hearth on mobile oven

You don't have to wait three weeks for the under floor vermicrete to dry but it will take longer to dry once it's built over. The underfloor vermicrete should be 5:1 for adequate strength. The vermicrete over thedome should've about 10:1 for adequate insulation.

[kirshner]

Re: making fire hearth on mobile oven

people have written vermaculite, cement ratios ranging from 12 to 1 to 5 to 1.
so I went 7 to 1, but will go 5 to 1 for outside dome( I think)

[kirshner]

Re: making fire hearth on mobile oven

thanks for the healthy debate
I will get some fibre board to go on top of vermaculite before i cast hearth then,
do I really have to wait 3 weeks for vermaculite to dry before I cast floor,because then I will have to wait another 3 for hearth to dry,I want to use it in 4 weeks.
dome has been drying now for 3 weeks.

[david s]

Re: making fire hearth on mobile oven

Yes, board might be ok but blanket is too soft. 100 mm vermicrete is sufficient. He's also using castable, not bricks

[Laurentius]

Re: making fire hearth on mobile oven

Wouldn't you say "A ton of Bricks", also compresses the ceramic boards, upon which its sit? Isn't the (maxim) here is: Insulate, insulate, and insulate????

[david s]

Re: making fire hearth on mobile oven

With 100mm of dense refractory castable sitting on top of ceramic fibre blanket it is likely to just compress it, your 100mm of vermicrete should be sufficient insulation on its own. Use a 5:1 vermiculite, cement ratio and let it dry for about 3 weeks before building over it.

[Laurentius]

Re: making fire hearth on mobile oven

I meant vermaculite, I'm not familiar with vesuveus. Are you using the steel plate as a reservoir for heat or for structural stability? If you are not using it for heat, I would place the ceramic blanket on top of it to minimize the heat transfer.

[kirshner]

Re: making fire hearth on mobile oven

when you say,Vcrete I assume you mean the vesuveus concrete not the vermaculite and concrete,
if so interesting point about not making it too compact will check it out
thanks.I have some spare ceramic insulation blanket which I might strap under the steel plate if it heats up to much

[Laurentius]

Re: making fire hearth on mobile oven

The Vcrete will be as effective as its thickness and consistency are properly maintained. Too thin a layer or too compacted, its almost useless.

[kirshner]

Re: making fire hearth on mobile oven

thanks for the replies,
A few things to explain,
I realise that a concrete slab usually goes under the insulation as a base for it to sit on,I didnt think it was necessary here because the base of my structure is a thick steel plate,very heavy cant remember exact width.
this plate is above the wood storage area, its high so wont touch the wood.
so on the plate i have 100mm deep of vermaculite, on that I have a 50mm concrete slab which is made from a refractory cement the mix designed for heat and strength.
and finally on top of that I have 50mm deep of vesuveus premix as the fire hearth,
this premix was recomended to me by a company that makes ovens and it is what they used to make firewall domes,its not the joint compound.
this suff was expensive ,would never just use plain concrete.
thanks david I will do it in 2 halves,and use the pins
under all those layers how hot do you expect the plate to get realistically isnt the vermaculites job to keep that heat to a minimum,plus the wood entrance will be open to the air

[david s]

Re: making fire hearth on mobile oven

It wont work, that is just a thin joint glue for sticking fire bricks together with.

It depends what Vesuvius product he has, they make a wide range of refractory products including castable refractory. He may well have the correct one.