floor tiles

[artigiano]

would 2.5 - 3 inches of vermiculite concrete in the hearh slap be just as efficient or at least close to the insulation board? Also, how many inches should i leave to be filled between the dome and outer walls. My last oven I only left a couple inches and I have some cracks in the outer wall bricks. Is this due to the heat?

[maver]

would 2.5 - 3 inches of vermiculite concrete in the hearh slap be just as efficient or at least close to the insulation board?

The insulation board is significantly better as far as insulating properties, but there are lot's of us here who have constructed with vermiculite or perlite concrete and have a very good home oven. I think for "always on" commercial use you would certainly want the superior insulation of insulation board, but for an oven used 1-2x/week both are options. If you are trying to extend the length of your retained heat baking time you might have better success with insulating board, but other issues such as preheat time and thermal mass affect this more.

Also, how many inches should i leave to be filled between the dome and outer walls.

The general recommendation is six inches of loose filled perlite/vermiculite is ideal, or replace that with 1 inch ceramic fiber insulating blanket for 2 inches of loose fill (1 inch blanket plus 4 inches loose fill should be similar to 6 inches loose fill). As James has pointed out in the past, the insulating blanket is really better, as it "stops" the heat closer to the refractory layer, but again, either is very useable for the home oven.

My last oven I only left a couple inches and I have some cracks in the outer wall bricks. Is this due to the heat?

I don't know, were the bricks getting hot? I would imagine even a couple inches dropped the translated heat enough that conventional bricks shouldn't be prone to cracking, but if they got wet and then also quite hot at time that might have done it.

[texassourdough]

Floor Tiles vs. Bricks

I installed a Casa 100 which of course has the "interior" floor tiles (surrounded by the dome with the dome resting on the insulating slab. I had a mason assisting me and he did the actual setting of the floor tiles. They are pretty smooth but I have to comment that ANY unevenness in the floor tiles will lead to angst. I will be moving in about three years and will definitely build another oven. I am toying with building a Pompei. However, I have to say that concern for getting the floor bricks even is a significant concern of mine. I am surprised more home builders who use brick don't express more encouragement of being damn sure the bricks are smooth for I can envision that as a major headache!

As bread is one of my major interests, I am particularly concerned with heat retention also. I like the "dome over" or "dome surround" approach of the Casa oven as it gives, I think, a better heat seal to the oven.(though I acknowledge that is somewhat speculative. Were I to build a Pompei I would probably cut the floor bricks. I like that concept.

As an aside one area where I know my oven is "weak" is that I oversized the slab on which the oven sits and one of the interesting phenomena of an oversized slab is that it sucks heat out of the floor. My next oven will have an insulating slab that is barely big enough for the oven and insulating layers in order to minimize heat loss to the slab. (NOTE: this is not a biggie - this is a fine detail, but...one that others who want the most efficient oven possible might find useful.

[james]

Artigiano,

I am pretty sure you are building a commerical oven. Is that right?

If you are building an "always-on" oven, I would recommend seriously insulating the top and bottom. If the cost of the modern high-efficiency insulators is an issue, then at least use serious layers of vermiculite under and around the oven. The Modena we sell as 6" of high tech insulation undernearth and 4-8" of high tech insulation above -- to keep the walls cool when you cook.

There are a handful of good reasons why this is important. You don't want to heat up your kitchen; you don't want to have to buy twice as much wood; you don't want to worry about your oven giving up heat in the middle of dinner; and you don't want to have to worry about re-heat times every day.

We have had postings and emails from restaurant owners and chefs asking what they can do about their under-insulated oven, and what a pain it is.

So, you have the opportunity to get it right -- from the get go.

Jay, did I say "nice bread photos" yet? You bread looks great. How did it taste?

James

[artigiano]

Thanks James,

You read me like a book... you are correct I am planning on designing and at least having a hand in the building of a commercial oven, its kind of a dream I have. It may be a while yet, but I am working away on it. The vermiculite is easily accesesible to me and sounds more cost effective. I can definately put 6-8 inches between and above the dome. As for under the floor tiles I was thinking I should be around 4 inches inside the refractory slab. I would use a round form inside the form for the entire slab. What do you think? Is this well enough insulated, I am very open to anything you guys can advise me on. Yes, I have also been advised never to build my own commercial oven, but thats advice I am probably not going to take so anything besides that would be very nice. Should the vermiculite around the dome be loose? What mix ratio would you suggest inside the slab? How many inches of just refractory concrete should I leave under the floor tiles? I have found 3" tiles but you have informed me that this is too thick. In contrast with the brick I thought it would be okay.. but if you still think they are wrong I will do some more searching. I am planning to clad the bricks with 2.5" refractory concrete around the dome. I have been tinkering with this for a while.. well just about anything when it comes to traditional pizza. I finally got my dough right, after a year of trial and error and a lot of research (yes, even dough took a while to research). Now, since I can't get fresh mozzarella curd on the west coast to make fresh mozzarella, I am in the trial runs of making the curd for the stretching process from milk. I have had moderate success, but I am determined to get it right. I have been using bacterial cultures and enzymes coming from back east to curd the milk for the mozarella. I just have to make sure its going to make sense for me to do it this way and have to make sure the process is not going to take too much of my time.

[artigiano]

Thanks James,

You read me like a book... you are correct I am planning on designing and at least having a hand in the building of a commercial oven, its kind of a dream I have. It may be a while yet, but I am working away on it. The vermiculite is easily accesesible to me and sounds more cost effective. I can definately put 6-8 inches between and above the dome. As for under the floor tiles I was thinking I should be around 4 inches inside the refractory slab. I would use a round form inside the form for the entire slab. What do you think? Is this well enough insulated, I am very open to anything you guys can advise me on. Yes, I have also been advised never to build my own commercial oven, but thats advice I am probably not going to take so anything besides that would be very nice. Should the vermiculite around the dome be loose? What mix ratio would you suggest inside the slab? How many inches of just refractory concrete should I leave under the floor tiles? I have found 3" tiles but you have informed me that this is too thick. In contrast with the brick I thought it would be okay.. but if you still think they are wrong I will do some more searching. I am planning to clad the bricks with 2.5" refractory concrete around the dome. I have been tinkering with this for a while.. well just about anything when it comes to traditional pizza. I finally got my dough right, after a year of trial and error and a lot of research (yes, even dough took a while to research). Now, since I can't get fresh mozzarella curd on the west coast to make fresh mozzarella, I am in the trial runs of making the curd for the stretching process from milk. I have had moderate success, but I am determined to get it right. I have been using bacterial cultures and enzymes coming from back east to curd the milk for the mozarella. I just have to make sure its going to make sense for me to do it this way and have to make sure the process is not going to take too much of my time.

[james]

How you set your floor depends on what you are using. Brick floors and some round floors (the Artigiano for example) can be set in sand (or a sand/fireplace paste) because the edges are square and they line up tightly and hold each other in place.

Other floor pieces, such as the round pie-shaped pieces for the Casa, Premio and Ristorante are curved to leave a joint for refractory mortar than closes the seam and helps holds them in place. They are also rough on the bottom, so a bed of refractroy mortar helps get them smooth.

Beyond that, there really are not any thermal issues or expansion issues. It is more of a practical installation issue. Both method perform the same when cooking and cool down the same.

I'm not sure where the rectangular floor tile fits in, and whether they should be set on sand/clay or mortarted in place. If they have straight edges and a smooth bottom, and fit tightly together, it would seem as though you could set them on sand/fireclay.

On the cast-your-own question, I would not do it myself. I have handled a lot of oven pieces and done quite a lot of concrete work (of course not as much as pro mason), and I wouldn't take it one. A home cast floor would be really hard to get right. You would have to spend a lot of $ on expensive refractories -- both for alumimate and the aggregate itself, and you would have to do a great job of polishing it to get a smooth surface, and I'll bet it would still have high spots and low spots, and would probably crack. Plus, the home-cast floor would be air dried, where at least firebricks are fired. If you don't want to buy an FB oven, I think firebricks are the best alternative.

James

[artigiano]

Hi James,

I wouldn't dare cast my own floor, or dome. I would buy the tiles and brick, make any nescessary cuts to them and was thinking about mortaring them straight onto the refractory concrete.. I have heard and read about this sand fire clay mixture and not sure I even understand it. I think that its a high sand to fireclay ratio and I don't understand the reason when mortar should do the trick? For the joints I am thinking that it would be quite tight and i could always make a wet fireclay mix so that it can go in between those joints and I could sponge off the excess.. and work the fireclay down.

[maver]

fireclay properties

My understanding is the fireclay provides refractory function (ability to quickly transfer heat through the material - opposite of an insulator) in the mortar but does not contribute much to structural support. Sand does well for load bearing and is therefore the primary ingredient in most mortar. The lime and portland cement (or in a commercial oven the calcium aluminate cement instead of portland) provide "stick" - adhesive strength between the bricks. If you have played with fireclay without an adhesive (as most of us used to apply oven floor bricks to the hearth) you'll appreciate that while it can hold a shape, it continues to crumble pretty easily once dry, unlike a good mortar.

[james]

If you are using bricks for your floor, the edges will be tight enough to where you won't want, or need, anything between the (such as sand or clay). If you carefully site the right up against each other, there should not be enough of a gap between the for anything to get in. The bigger issue is tapping the down into your sand/clay mixture to get right of as many of the "peel catching" ridges as you can.
James

[maver]

missed point

Ahhh, I missed this had moved to a floor discussion. I think the principle still remains the same though, that rather than mortar the floor down you want a level surface (which the wet or dry sand/fireclay mix allows you to create) and some lateral slip to allow for expansion/contraction, which is where the fireclay sand mixture differs from mortar.

[carioca]

Isol board

From this discussion I derive the implicit info that we're shooting for a level surface - to me as a naive builder that means: no sand, no mortar no refractory goo needs to go under the tiles when you've got a flat and level isolation board in place ?

But my hearth tiles (250 x 250 x 50 mm) are pretty rough on both surfaces, hence my new question here: can one make a nice fuid 'wash' of refractory mortar to sweep over the tiles, perhaps with a squeegee?

Ciao

[maver]

grit

The sand/fireclay mixture (especially with Alf's sugested refinement of the instructions of applying the mixture dry, then watering it to give it some 'stick') is probably a better way to go than using a wash because you can be more careful with the mixture to level the height of all the floor bricks - applying a wash would likely introduce more error. And if you mean to apply it to the cooking surface of the bricks I would be concerned about introducing grit into your food - it would not be as hard as the fired surface of a fire brick. Do your best to level the hearth floor, then allow any imperfections in the cooking surface to fill with ash - it will not affect the food as much as refractory grit will.

[Hendo]

Grit

On the issue of achieving a smooth floor, I have noticed references to a concrete surface grinding wheel (not an angle grinder) which could be used to smooth out any high corners or edges of the hearth bricks after they are laid. While this seems like a good idea, is it possible that the food will pick up refractory grit from the ground surfaces?

[artigiano]

Hey guys,

I previously used this stuff called bondset. It is a refractory mortar, and is kind of like a glue but takes a long time to dry and I think the heat from firing up the oven is what allows it to fully cure. I was able to achieve a nice level surface and I actually used this stuff throughout the whole dome. In this sand and fireclay mix what would the ratio be? I heard something like 9:1 but that seems like a lot of sand? Also how thick should this layer of sand/ fireclay be? The bondset I used was around 1/4 inch over the refractory concrete that had the vermiculite insulation. What do you think of my approach for the home oven? I have no complaints a very level surface using individual bricks not even floor tiles... but was wondering if there are added benifits other than a level surface when using the sand/ fireclay mix?