pompeii oven construction began today

[paulages]

marcel,
i have not had any visible problems with an expansion differential between my insulating layer and my refractory mortar/brick layer. granted, mine is a manufactured refractory insulator and not perlcrete, but they should act somewhat similarly. i would suggest that you ditch the aluminum foil and move forward...but i don't mean to talk you out of "overdoing it."

[Marcel]

Aluminum foil rationale:

#72

(M) Hi Fred,

You asked:

Jim
<snip> So I was wondering if the major reason for the aluminum foil between the dome firebrick and the Vermiculite/cement cladding is to reflect heat?

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(M) I don't remember who wrote what follows but I saved it. It is one builder's rationale for using foil:


(?) "This is ordinary aluminum foil from supermarket, sold in 2 or 3 widths and thickness, get the stronger one while considering the price as well. This foil has one main role to play. It is not there to reflect heat back; there is no light, why would you want to reflect heat away from cladding? We need heat in the cladding. The foil prevents concrete bonding with firebricks, which is the main reason. Other then that this foil also stops firebricks to absorb water from soft concrete when it is applied. Instead of aluminum foil candle wax or plastic wrap could be used, but it would burn and be felt in the air for the 2 first firings."


================================================== ====


(M) Although I am having difficulty getting the perlcrete to adhere to the foil, in general I agree with that writer. One factor not mentioned there was that foil would also tend to stop any leakage of smoke from cracks in the refractory layer that virtually (or completely) covers the fire bricks.


(M) In the quote above, that builder, I believe, suggests putting the foil between the firebricks and the layer of refractory mortar. In my case, I will have an insulating layer of perlcrete so I do want to reflect heat back to the firebrick. I'm not sure that foil would work as a heat reflector, absent light but the thermal engineers who read this may be able to shed light on that question.


(M) Since placing perlcrete at the top of the dome should not be an adhesion problem, I will, at a minimum, clad as much of the external dome top with perlcrete. When it starts to slide off, I will look for other solutions. I will ultimately house my igloo and pour loose dry perlite over the dome. That will provide a lot of insulation but will not protect my dome from the rain until I get the roof built. The foil placement may, in my case, be an exercise in futility.

(M) If you use the foil remember to start to place it from the bottom up, just like roofing tiles so that any water that gets through will not get under that foil layer.

(M) I believe that not many Pompeii builders bother with the foil but like Paul's adage states, I prefer to "overdo or don't do it at all".

Ciao,

Marcel

[fdn1]

Reason for aluminum foil?

Jim
Sorry if this question has been addressed previously but I do not remember reading about it in the plans on the internet for the Pompeii style oven. So I was wondering if the major reason for the aluminum foil between the dome firebrick and the Vermiculite/cement cladding is to reflect heat?

[Marcel]

12:1 seems to be a weak mix

(M) Jim wrote:

"For any large enclosure, it's cheaper to coat the dome in a 4-6" mix of perlite/vermiculite & cement (the 6 or 8:1 ratio) and then house it. Loose fill will be somewhat more energy efficient but probably not noticeably with our use. This would probably save you 2/3 or 3/4 of the loose fill needed.

Jim"
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(M) Tarik, if your last post was not a typo, I think 12:1 would not offer enough adhesion. I used perhaps a 7:1 and could not get it to stick to the aluminum foil (hardly a surprise); but even after adding Paul's chicken wire, it fell off. Cement is cheap but perhaps you simply want your cladding to be as "insulatory" as possible.

Ciao,

Marcel

[aikitarik]

For any large enclosure, it's cheaper to coat the dome in a 4-6" mix of perlite/vermiculite & cement (the 6 or 8:1 ratio) and then house it. Loose fill will be somewhat more energy efficient but probably not noticeably with our use. This would probably save you 2/3 or 3/4 of the loose fill needed.

Jim

Jim,

I'm just about at this stage... would it really be more efficient to do the loose fill and no perlite concrete layering? I was planning on a 12:1 mix, about 4-5 inches thick and than using loose fill around that.

My main concern was to prevent perlite dust from getting into the oven and to add a little more structural support around the chimney.

Tarik

[paulages]

yeah, i probably "overdid it," since i already had the castable insulation around the dome which was performing pretty well. i just have a hard time cutting corners i might not have the opportunity to fix. i certainly didn't go the bare bones cheapest route on mine, but i can also see how one could spend twice as much.

haven't heard from you for a while, jim. good to see you back.

[james]

We have set concrete board at an angle in the back corners of the enclosure to reduce the amount of vermiculite you need, while maintaining the thickness we want.

James

[ColonelCorn76]

marcel, i'm afraid to tally the bill for this thing, but the perlite cost me $112 for 14 bags.

For any large enclosure, it's cheaper to coat the dome in a 4-6" mix of perlite/vermiculite & cement (the 6 or 8:1 ratio) and then house it. Loose fill will be somewhat more energy efficient but probably not noticeably with our use. This would probably save you 2/3 or 3/4 of the loose fill needed.

Jim

[paulages]

same size: 4 cu/ft per bag. i had to really chase down a deal, but even at portland nursery, where i thought i'd end up having to go, they are $10/ bag.

[Marcel]

How many Cu./Ft. per bag at $8?

#64

(P) "marcel, i'm afraid to tally the bill for this thing, but the perlite cost me $112 for 14 bags."

(M) That works out to $8 per bag. I pay $12.99 per bag that holds 4 Cu/Ft. How much volume do you get for $8? ____

Thanks,

Marcel

[paulages]

marcel, i'm afraid to tally the bill for this thing, but the perlite cost me $112 for 14 bags.

[Marcel]

Pizza with Oregone-no

#63

(M) Thasapizza to spice up your life!

(M) I notice the ubiquitous bottle of beer as well in one of the images.

(M) Paul, that suggests you spent close to $200 .... just for the perlite fill. Have you totaled your costs to date? I'm up to about $1,500 ( counting the tile saw, and the angle grinder, etc.) and I haven't even clothed her yet, unless you call a tarp clothing.

(M) For non Oregonians, we in this part of the northwest say you don't tan here, .... you rust.

Chow?

Marcel

[paulages]

upper roof goes on

i framed in my roof proper yesterday, and got it sealed up just in time for a torrential windy downpour all night long. i don't have a chimney cap yet, but the retained heat from yesterday's fire kept the landing dry. i still have to build a curb around the edge of the roof, fill it with soil and plant it, but the chimney flashing is on (i used high temp. metal roof to chimney flashing, to get a good seal on my pondliner) and the liner is covering the surface.






there won't be quite that large of an overhang on the side left in the picture.

p.s. check out the sad wet pieces of pizza left out overnight

[paulages]

perlite in/closing up the durarock roof

this took 14 bags (4' cu) of perlite, and could have fit at least 2 more. my guesstimate was 16, but i was trying not to have to return any so i bought short of that #. should've stuck to my intuition. oh well, good enough.

[paulages]

walls are up, perlite in...