Beautiful craftmanship

[dakzaag]

Re: Beautiful craftmanship

I think either brick or board is acceptable. The board is easy peasy to install and away you go. The brick would need to be set and probably leveled a bit. All of the insulating brick i have seen are fairly irregular, but I have not seen very many.

It really comes down to availability I guess. I have a hard time sourcing the board. (at least at a reasonable price.) That is why I started digging around looking at the insulating brick.

Mixing perilite/vermiculite/zonalite etc with a bit of Portland is by far the cheapest.

[S1MON]

Re: Beautiful craftmanship

The airset/water soluble is really only suitable for minimal joints, <1/4", while the powdered on is normally fine up to and beyond half inch.

2x4x8 insulating firebrick around here are $7.00 each for a SqFt cost of $31.50, 2" ceramic board is $17.78 per SqFt.

The bricks differ in value depending on size. A 3" (76mm) thick brick cost less than a 2" one, and by volume offer the best value by far. I believe this is because it's the standard size to use, and is produced in far greater numbers.

So a 230x114x76 brick is ?1.49 + VAT -> ?1.79 (about $2.77 at the moment)
(9 x 4.5 x 3 in inches)

CalSil, 1220x500x75 is ?44.99 + VAT -> ?53.99 (about $83.68)

If my math(s) is correct,

Bricks are $9.81 per square ft, 76mm thick

CalSil is $12.74 per square ft, 75mm thick.

My supplier doesn't list ceramic fibre board, but I believe it's quite a step up in price here.

[Tscarborough]

Re: Beautiful craftmanship

The airset/water soluble is really only suitable for minimal joints, <1/4", while the powdered one is normally fine up to and beyond half inch.

2x4x8 insulating firebrick around here are $7.00 each for a SqFt cost of $31.50, 2" ceramic board is $17.78 per SqFt.

Edit- Perlcrete works out to less than $2.00 per SqFt for a 4" layer, FYI.

[S1MON]

Re: Beautiful craftmanship

If you really want to know what they were using, just send Alex an email and ask.

That would be the easiest

I was just asking out of curiosty really, it's not important exactly what type of clay I guess, just knowing that's how they build for easy dismantling was enough.

Further to my looking at the use of insulating fire bricks as it appeared they used, I found lots of values for similar materials, and it generally seems that the insulating boards are better. I did contact a supplier for data sheets for his particular items and here's the relevant data (to me anyway). It's all in metric I'm afraid

2300F (1300C)* grade insulation brick
Cold crush strength 2MPa, or 2N (per mm squared).
Thermal conducticity 0.23 W/mK at 350C (Lower is better)
Density 800 Kg/m^3

Calcium Silicate board (1000C grade)
Strength 2.6MPa, or 2.6N
Thermal conductivity 0.08 W/mK (at 200C)
0.1 (at 400C)
0.12 (at 600C)
Density 225 Kg/m^3

So whilst (for me at least) the board is slightly more expensive, it would appear to be well worth the extra on thermal conductivity alone. Being lighter and stronger is a nice bonus. If your supplier charges more for the bricks, then they're really not good value compared to the boards.

This has all gone a bit off topic...

* 2300F is 1260C, but sheet showed data of 1300C

[dakzaag]

Re: Beautiful craftmanship

The clay is typical ceramic clay like you would use for a bowl or pot. Cheap and easy to work with.

It is probably not accurate to suggest that the hydraulic is better than the air set, it is more a matter of which is more appropriate.

If you really want to know what they were using, just send Alex an email and ask.

[S1MON]

Re: Beautiful craftmanship

Insulating firebrick are expensive, more so even than ceramic board.

Do you know how they compare on insulation values, (having a little trouble finding data for some reason).

I've just checked prices for 3" thick insulation bricks against 3" Calcium Silicate board, and the bricks are cheaper per area covered. (77% of the price).

[Tscarborough]

Re: Beautiful craftmanship

Insulating firebrick are expensive, more so even than ceramic board.

[S1MON]

Re: Beautiful craftmanship

Thanks for the reply dakzaag.

I watched the video again, and it looks like the oven base was probably built by local tradesmen, Alex and friends 'just' build the oven on top.

So the way the video shows it, they're only working with refractory materials. My suspicion is that they're using a dry mortar to mix on site. Here in the local refractory suppliers, there seems to be two types of mortar, pre mixed wet air set/dry mortar, and the dry powder hydraulic setting mortar. Of the two the hydraulic mortar seems best to use.

Another thing I noticed that I didn't on first viewing, was that they seemed to use two courses of insulating bricks as their insulating layer under the oven. I've not seen that done before with any of the home built ovens. I'll have to investigate as to why, whether it's cost, time to lay the bricks, or perhaps insulation values. It's one more option for builders though.

Thanks for the info on the clay mortar mix for the temporary builds. Is it fireclay? I've read of another type of clay on the forums, but can't recall what it's called, and if that could have be used in this case.

The MHA meets do look interesting, and a rare opportunity for experts in this field to meet, exchange ideas, and of course experiment. Everyone seems to benefit and have fun! I've looked though a few meetup galleries, and the heaters are interesting, but don't see myself ever building one. Naturally the oven builds grab my attention more.

Simon.

[dakzaag]

Re: Beautiful craftmanship

oops, kinda left you hanging there s1mon.

Firebrick and refractory mortar go hand in hand, doesn't matter if your building a pottery kiln, pizza oven or masonry heater. Most of the information and materials apply across these varied industries.

Regarding the mixing you observed, I do not remember noticing this but it could be several things. Refractory cement will dry out just being exposed to air and it needs to be brought back to a workable consistency with water. So you could have been observing them just reconstituting the mortar.

They also could be using a dry product that needed to be mixed with water before use.

It is also possible that they started some of the exterior masonry work which would require some mixing as well.

As far as the temporary builds are concerned, for the most part the ovens are constructed with clay mixed to a mortar like consistency. Once the ovens are fired the clay begins to vitrify. Frankly they are pretty stable at this point. By the end of the week, the ovens are demolished and examined for clues to indicate how the particular structure and design preformed during it's short life.

Several pizza ovens are constructed and a pizza party is enjoyed by all attendee's on Friday evening. The pizza party is the highlight of the week even though the focus is on masonry heaters and many of the masons get to show off their culinary chops making pizza and drinking beer. A good time is had by all and I have to admit it tripped a trigger inside of me that I did not know existed.

Sorry I lost track of this thread, hope I answered your questions.

[S1MON]

Re: Beautiful craftmanship

Hi dakzaag, couple of queries you may be able to answer for me.

In the video they appear to use pre-mixed mortar, but they mix it up as it may have seperated. Is this correct, and would they use the same mortar for ovens and masonry heaters?

Secondly I've seen pictures from the MHA meet ups, and they build temporary heaters and ovens for teaching and experimenting purposes. I'm curious as to what mortar they use/mix up to enable an easy tear down afterwards.

Thanks, Simon.

[Dennis Ferraro]

Re: Beautiful craftmanship

I am a plumbing contractor by trade an really appreciate craftsmanship. My wife an I are thinking about opening a small pizzeria, we took a ride to Montana last weekend to look at a place. It has a wood burning oven that I would take out and start over it was not built very well.

[dakzaag]

Re: Beautiful craftmanship

yes I am. How about yourself?

[Dennis Ferraro]

Re: Beautiful craftmanship

Thank you for the video link he is definitely a craftsman. I take it you are a mason by trade if you attended the week long convention?

[TropicalCoasting]

Re: Beautiful craftmanship

Wow I did not know that, but looking at his work I have no problem believing it. I love his attention to detail, his web says he does not using any forms when building the dome of his ovens.

My neighbour in Melbourne was an old Greek stone mason from the Island of Lesbos.(he used to build mainly stone bridges)
He couldn't read or write or even speak much English I spoke half a dozen Greek words he spoke half a dozen English words and the rest was hand gestures and smiling.
We became great friends and over time he did some amazing building works for me fountains garden beds and included a pizza oven for himself(portable on a metal stand with wheels,he made that too) ,he offered to build one for free for my parents but they didnt have the room.
All his work was done by hand all his measurement were by eye and his thumb on a stick.
I moved and havent seen him for 15 years ,he was well into his 70s then.
I will try and see him if he is still alive next time I go.

[dakzaag]

Re: Beautiful craftmanship

Here is the big oven he did in New Zealand for Chef Al Brown. The video is mostly about the bakery, but they show the build in really fast motion.

In April of 2014 Alex chaired a presentation at the annual Masonry Heater Association meeting in North Carolina. I attended the week long convention and was able to watch Alex build a wood fired oven with only hand tools. We had a few opportunities to interact and he very patiently answered all the questions I could think of. He has also responded to several email inquiries that I have sent him since April, so now I call him a good friend. (doubt if he would know me if I walked into his shop tomorrow, but...)

I have not considered having him do work for me, but I will openly admit to copying several of his designs. If imitation is the greatest from of flattery, then I guess I am guilty. I really like the approach Alex takes to his projects and his philosophy on a variety of topics seems to match my way of thinking.