Last Minute WFO questions before starting dome!

[Abouna]

OK, after our vermiculite semi-fiasco (3:1 mix should have been 5:1) we've ordered some Super Isol board to compensate for the mistake.  Hearth floor should now be quite nice, if 1.5" taller than planned!

We do have a few problems that I can't work out:

- what can we use for the fireclay under the firebrick floor?  I can't seem to find it locally (you'd think a city of nearly 200k would have these things!).

- refractory mortar.  Again, the only thing I've found locally is Alsey Flue-set pre-mixed.  Now at $25/ 10lbs bucket, it's going to get very expensive very soon.  What are my alternatives?  I've heard mention of a homebrew option but I think it uses fireclay (again, I can't get that here).

- We've ordered 240 bricks, is that going to be enough for a 48" Pompeii style?

[Polo]

Where are you located?

[Abouna]

Where are you located?

Cedar Rapids, Iowa

[breadstoneovens]

- what can we use for the fireclay under the firebrick floor?  I can't seem to find it locally (you'd think a city of nearly 200k would have these things!).

If I understand right the floor of your oven will be made of firebrick, correct? In that case you can use regular bricks since the firebrick will take most of the thermal shock and are made for it. The idea is that the floor of the oven is made of a material that doesn't break over the multiple times it will heat and cool, as it would end-up in your food. The firebricks will play that roll. Underneath it, whatever materials you will use may crack over time but it won't matter as it won't be in contact with food. Most likely it shouldn’t lose its structural integrity either.
Now be careful to not create too thick of a floor as it will take longer to heat up. 3" to 4" is good over that it starts to be a lot especially if you are going to cook mainly pizza.

Good luck,

Antoine

[breadstoneovens]

- We've ordered 240 bricks, is that going to be enough for a 48" Pompeii style?

How are you laying your bricks? The smallest side facing inside the oven? Are you planning on cutting them in half?

[Abouna]

If I understand right the floor of your oven will be made of firebrick, correct? In that case you can use regular bricks since the firebrick will take most of the thermal shock and are made for it. The idea is that the floor of the oven is made of a material that doesn't break over the multiple times it will heat and cool, as it would end-up in your food. The firebricks will play that roll. Underneath it, whatever materials you will use may crack over time but it won't matter as it won't be in contact with food. Most likely it shouldn’t lose its structural integrity either.
Now be careful to not create too thick of a floor as it will take longer to heat up. 3" to 4" is good over that it starts to be a lot especially if you are going to cook mainly pizza.

Good luck,

Antoine

It seems I'm not being completely clear.  Here's what we've done:

3.5" concrete slab
4" vermicrete 3:1 hearth slab
1.5" Super Isol board
thin layer of fireclay for perfect level?  This is the bit I can't source.  Am I misunderstanding the use of fireclay here?
firebrick cooking floor

How are you laying your bricks? The smallest side facing inside the oven? Are you planning on cutting them in half?

We're going to use half bricks.  I assume the smallest side facing inward.  This is my wife's territory, she'll be building the dome.  She's using the FB plans as a guide.

[buceriasdon]

Sand is fine if you can't locate fireclay. Many years ago I busted up a bunch of old bricks just to have fireclay, I'm too old for that nonsense now.
Don

[breadstoneovens]

1.5" Super Isol board
thin layer of fireclay for perfect level?  

I would use nothing. The Isol Board should be pretty flat already. So just lay the firebrick right over it. If you have a low point some sand, as mentioned later, can be sued.

For the number of brick if your oven is 48", then:
(4x3.14x(24x24))/2=3617" square is your oven dome surface.
Each brick on the small side is 4.37*2.68=11.7" square
3617/11.7=309 bricks required for the dome or 155 bricks cut in half
Floor radius is 24 (48"/2) + 4.5 (9"brick cut in 1/2) =28.5
Floor surface is 3.14*(28.5*28.5)=2550" square
Each brick on the mid side 9x4.37=39.3
2550/39.3=65 bricks

155 for the dome plus 65 for the floor = 220

Please someone double check my math but I think you should have enough brick to do your oven and a landing area in front of your oven.

Antoine

[Ev]

For the refractory mortar, do not use the pre-mixed stuff in the bucket. It's water soluble and is made more for filling in narrow cracks than laying brick. Try to find "Heatstop 50". A decent contractor supply yard should have it. It's a bit pricey but it's the best product for the job. If you can't find fire clay, you can't make a homebrew mortar, unless you use a wet/tile saw and cut most of your brick first and save the sludge in the bottom of the pan. That's fire clay. If you do that, a very usable refractory mortar can be made using equal parts fine sand, fire clay and portland cement.

[Abouna]

For the refractory mortar, do not use the pre-mixed stuff in the bucket. It's water soluble and is made more for filling in narrow cracks than laying brick. Try to find "Heatstop 50". A decent contractor supply yard should have it. It's a bit pricey but it's the best product for the job. If you can't find fire clay, you can't make a homebrew mortar, unless you use a wet/tile saw and cut most of your brick first and save the sludge in the bottom of the pan. That's fire clay. If you do that, a very usable refractory mortar can be made using equal parts fine sand, fire clay and portland cement.

Ev,

Thanks for that.  I think I've found a local place that has Heat Stop II (same as 50 but in 10lb buckets).  Since they don;t have the 50lb bags they are thinking about selling me the 10lb buckets at the 50 lb rate. 

Still, a lot of money!

[Ev]

Once again, if it's a pre-mixed paste, it's not the same and should not be used as mortar. Read the label thoroughly before you buy it.

In case you don't already know, you should be able to order HS 50 and or fireclay from Forno Bravo if you can't find it elsewhere, though it won't be cheap with shipping and all.  Also, FWIW, I think I used almost 2.5 bags of HS50 when I built my 42" Pompeii. I also made a fair amount of the homebrew to use as cladding on the outside of the dome.

[Tscarborough]

Heatstop is a great product.  The wet stuff is fine for fireplaces, and some types of ovens, but not for round ones (the joints are too wide).

[buceriasdon]

Steve, The only difference is in the packaging size. Both are dry mortars.

[Abouna]

Well, back to square one!

Cripes, we're not getting anywhere.  The place that wanted to sell me Heat Stop II in the 10lb pails wants $120 for 4 of them.  It would likely cost me upwards of $400 to get the job done at that rate.

I'm now trying to get a cement supply to get me some Alsey Flue-set in 50 lbs.  It's 60 miles away and they don't know if they have it.

I wish I could get fireclay, I'd just mix my own. 

This really stinks.

[Tscarborough]

That is crazy, I sell it for $21 a bucket or $55.00 for 50#, and I am not doing it for fun. 

[Tscarborough]

I wonder what the freight would be on a 70# bag of fireclay from 78758 to your zip?  I sell it for .45 a pound, maybe it would be worth it to pay the freight.

[Abouna]

I wonder what the freight would be on a 70# bag of fireclay from 78758 to your zip?  I sell it for .45 a pound, maybe it would be worth it to pay the freight.

I have a UPS account, about $35.00

I also have a freight FedEx account.  Your prices are good.  How can I contact you if the Alsey thing doesn't work out?

[Tscarborough]

PM me here.