Filling joints in hearth slab?

[david s]

Re: Filling joints in hearth slab?

Guys, can anyone direct me towards whats considered a 'good set of instructions' for installation of any modular oven? I cant imagine they differ much but Id just like to compare some from a different manufacturer.

Thanks

Richard

Every manufacturers design will vary eg dome on top of floor or floor inside dome. Dome casting in one pice or dome in multiple pieces. Cast floor or separate fire bricks. Foil or no foil. Blanket or vermiculite etc. etc.
If you buy a kit it should come with comprehensive instructions, if not look for another.

[RichC]

Re: Filling joints in hearth slab?

Guys, can anyone direct me towards whats considered a 'good set of instructions' for installation of any modular oven? I cant imagine they differ much but Id just like to compare some from a different manufacturer.

Thanks

Richard

[mikku]

Re: Filling joints in hearth slab?

Thanks again Davids,
Seems like you never tire of answering the same stupid questions from newbies and not so new newbies.

Now I need to figure out what semolina is! And where to find it!

[david s]

Re: Filling joints in hearth slab?

Cast a little semolina on to the centre of the oven floor. If it turns black in 2 secs the floor is too hot. 3 secs, just right, 4 secs, not hot enough.

[mrchipster]

Re: Filling joints in hearth slab?

OK, a comedian this morning. My IR shows wildly varying temperatures, dome one temperature, floor another but hotter, sometimes pegs the meter that max's at 550C, then I point it at my hand it reads the same...I sometime think I'm hot but that is sizzling and in both instances a crock! Old farts cannot be hot!

I threw flour onto the hearth brick and it flamed while hitting the firebrick--a place where they mill flour must be a very dangerous place because of the chance of such an explosive fire. The places where the flour hits just makes a black spot and later difficult to get off or blackens the first pizza crusts! If not flour??? What?

I'm back to my old lazy habit of not searching previous posts...must be the newbie blood or just plain summer heat lazy!

Sounds like you need a new ir gun.

[mikku]

Re: Filling joints in hearth slab?

The beam of light from my IR thermometer.

OK, a comedian this morning. My IR shows wildly varying temperatures, dome one temperature, floor another but hotter, sometimes pegs the meter that max's at 550C, then I point it at my hand it reads the same...I sometime think I'm hot but that is sizzling and in both instances a crock! Old farts cannot be hot!

I threw flour onto the hearth brick and it flamed while hitting the firebrick--a place where they mill flour must be a very dangerous place because of the chance of such an explosive fire. The places where the flour hits just makes a black spot and later difficult to get off or blackens the first pizza crusts! If not flour??? What?

I'm back to my old lazy habit of not searching previous posts...must be the newbie blood or just plain summer heat lazy!

[kkgator]

Re: Filling joints in hearth slab?

I am often up too early to sometimes accurately describe what my thoughts are on any given subject. I agree that nothing inside of the oven should be mortared. My pics just show sand that was used underneath the floor tiles & the floor insulation. The only joint that should have mortar according to FB is on the outside of the composite pieces where they meet. The outside base where it meets the insulation should also be mortared. I have not mortared any joints or floor tiles as I agree with MRC that it should be loose to allow for expansion & contraction during heating & cooling.

[mrchipster]

Re: Filling joints in hearth slab?

OPEN FORUM QUESTION! What do you throw onto the hearth to see if it is hot enough?

The beam of light from my IR thermometer.

[mikku]

Re: Filling joints in hearth slab?

How big cracks are you talking about?
My bricks fit pretty tight, but they are a little uneven.
A few weeks ago, I used a small angle grinder with diamond cutting wheel to level the bricks--worked like a champ.

When I clean my oven for doing bread right on the hearth brick, I use a section of copper tubing and my airhose and compressor. I use my blow gun to direct air into the copper tubing--this loosens all the crap that is floating inside the oven. Keep it blowing and the crap stuff goes out the chimney. I have done this several times in prep of baking bread. In the case of pizza, I only use a bamboo street broom to move things out of the way.....the broom starts on fire--but that is OK. The majority of the ash is out of the way! What remains is seasoning for the first pizzas!

OPEN FORUM QUESTION! What do you throw onto the hearth to see if it is hot enough?

[davemartin88]

Re: Filling joints in hearth slab?

Hi there- for my casa 90 kit, the oven floor pieces rest on a bed of sand directly on the fiber board floor insulation, then the dome pieces surround the floor and also sit on the fiber board. I raked ashes in to the cracks from my first few curing fires and seems to work well so far!

[david s]

Re: Filling joints in hearth slab?

The composite oven pieces are grooved to fit on top of the floor & extend to the base. It is at the base where mortar needs to be applied as well as the small joint of the oven pieces. If you look at Dave Martin's build you will understand what I am describing.

Follow the instructions of the manufacturer, but your photos on your mobile oven clearly show that the dome does not sit on top of the floor, it sits on the insulation and the floor sits inside the dome. The gap between the floor and dome sections is better left empty and allowed to fill with ash IMO so the floor will have room to expand. Likewise the gaps between each of the floor bricks. If this is contrary to the manufacturers instructions I apologise, you should do what they say. As you have already filled them it may be too difficult to change anyway.

[kkgator]

Re: Filling joints in hearth slab?

The composite oven pieces are grooved to fit on top of the floor & extend to the base. It is at the base where mortar needs to be applied as well as the small joint of the oven pieces. If you look at Dave Martin's build you will understand what I am describing.

[RichC]

Re: Filling joints in hearth slab?

Thanks MrC! Lucky I asked.

[mrchipster]

Re: Filling joints in hearth slab?

Thanks Mr C, so ill just use mortar to stick it to the vermicrete slab underneath?
I assume that's ok?

NO! "The floor should not be mortared in any way!!!! It needs to float free.

Also, why isn't it mortared to the dome, seen as the dome sits directly onto the base?

The floor and dome expand and contract at different rates and bonding them together will promote cracks.

[RichC]

Re: Filling joints in hearth slab?

Thanks KKG, ill check that out