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Rob,
I use castable refractory which is a blend of CAC (calcium aluminate cement), high temperature aggregates and burnout fibres which assist in water elimination during initial firing. The stuff is expensive and you need to do a calculation of how much is required. As it’s rated to 1450C it uses high temperature aggregates that are way in excess of what we require. The use of lime in conjunction with CAC is a no no because it acts as an accelerant reducing the already limited working time of the mix. The stuff is also very temperature dependant. There are recipes out there (including this site) that recommend CAC and lime together. Unfortunately those that attempt it will find their mix going off as soon as it’s been mixed.Another alternative that works (just) for our temperature range is what we call homebrew. It is used as a mortar for brick builds and can be used as a castable. It is 3:1:1:1 sand, hydrated lime, Portland cement and powdered clay. Very cheap and good working time, but the lime is vicious on the hands, wear rubber gloves. It also requires the addition of the burnout fibres which can be the really fine polypropylene ones used in reinforcing concrete. They are finer than human hair and take extensive mixing to disperse in the mix properly. I also use them for adding to mortar if brick building as they provide some measure of reducing steam spalling wher mortar joints can be extremely thick.
Regarding my mobile, it sits on a timber trolley that has 6 wheels that enable me to roll it on and off the trailer easily.
On the subject of information sharing, most of us here are old farts and well beyond wanting to keep secrets in order to build empires. Rather, we are excited by the enjoyment of cooking by fire in ancient yet highly efficient designs and we want to “spread the love”.
Dave"
Hi Dave, I don't get to write here everyday so please excuse me if it seems long.
I can locate CAC here (Ciment fondu) though sourcing appropriate aggregate might fare a little more tricky, though not out of the question yet as I will try a few more places this week. I may just go with ref castable with 42% aluminate aggregate already in it for convenience. I will now be opting to keep mobile oven small-ish. (I read somewhere that your oven is 21"-is that inside measurement surely) alot smaller than the one I was planning originally (approx 750mm internal) but after much consolidating of the variables. I am now aiming at an oven around 600mm internal max-smaller if I feel I can get away with it.
I am thinking 50mm thick ref castable + adding the novomesh 950, (around 2%/100ml per 100litres of mix?) The polyprop fibres all melt out at 160C and in this application are only to aid the elimination of moisture through the curing process right. Do you think I need to add SS needles too, that is the question?
Finishing with a 50mm layer of fibre insulation blanket, covering dome and flue gallery, wire to secure it then 3 watered down layers of flexible acrylic pointing cement painted on surface leaving an expansion joint at the brick arch junction to allow for fluctuations. Would you be able to provide an example of the one you did or similar.
I am not entirely sure how best to figure out calculating amounts based on the sizes stated. I was told 2000kg per M2 but still a bit confused how to apply this info. Is there a formula I need to work with or a easy method with which to go forth?
I am definitely keen to avoid the tendancy to make an oven unecessarily big, after all a pizza shouldn't take that long to cook once heated, so cooking one 12" pizza at a time is fine. I actually opt for and prefer the opportunities it brings to enable people to prep, cook & eat together. You will be glad to know I not aiming for world domination here, Though I do appreciate the purist 90 second multi pizza brick oven view/approach too, and aspire to operate at around 450-500C. I have built a cob oven and operated a pompie esque oven before. So experience helps.
How does all that sound to you?
Rob,
I use castable refractory which is a blend of CAC (calcium aluminate cement), high temperature aggregates and burnout fibres which assist in water elimination during initial firing. The stuff is expensive and you need to do a calculation of how much is required. As it’s rated to 1450C it uses high temperature aggregates that are way in excess of what we require. The use of lime in conjunction with CAC is a no no because it acts as an accelerant reducing the already limited working time of the mix. The stuff is also very temperature dependant. There are recipes out there (including this site) that recommend CAC and lime together. Unfortunately those that attempt it will find their mix going off as soon as it’s been mixed.Another alternative that works (just) for our temperature range is what we call homebrew. It is used as a mortar for brick builds and can be used as a castable. It is 3:1:1:1 sand, hydrated lime, Portland cement and powdered clay. Very cheap and good working time, but the lime is vicious on the hands, wear rubber gloves. It also requires the addition of the burnout fibres which can be the really fine polypropylene ones used in reinforcing concrete. They are finer than human hair and take extensive mixing to disperse in the mix properly. I also use them for adding to mortar if brick building as they provide some measure of reducing steam spalling wher mortar joints can be extremely thick.
Regarding my mobile, it sits on a timber trolley that has 6 wheels that enable me to roll it on and off the trailer easily.
On the subject of information sharing, most of us here are old farts and well beyond wanting to keep secrets in order to build empires. Rather, we are excited by the enjoyment of cooking by fire in ancient yet highly efficient designs and we want to “spread the love”.
Dave"
Hi Dave, I don't get to write here everyday so please excuse me if it seems long.
I can locate CAC here (Ciment fondu) though sourcing appropriate aggregate might fare a little more tricky, though not out of the question yet as I will try a few more places this week. I may just go with ref castable with 42% aluminate aggregate already in it for convenience. I will now be opting to keep mobile oven small-ish. (I read somewhere that your oven is 21"-is that inside measurement surely) alot smaller than the one I was planning originally (approx 750mm internal) but after much consolidating of the variables. I am now aiming at an oven around 600mm internal max-smaller if I feel I can get away with it.
I am thinking 50mm thick ref castable + adding the novomesh 950, (around 2%/100ml per 100litres of mix?) The polyprop fibres all melt out at 160C and in this application are only to aid the elimination of moisture through the curing process right. Do you think I need to add SS needles too, that is the question?
Finishing with a 50mm layer of fibre insulation blanket, covering dome and flue gallery, wire to secure it then 3 watered down layers of flexible acrylic pointing cement painted on surface leaving an expansion joint at the brick arch junction to allow for fluctuations. Would you be able to provide an example of the one you did or similar.
I am not entirely sure how best to figure out calculating amounts based on the sizes stated. I was told 2000kg per M2 but still a bit confused how to apply this info. Is there a formula I need to work with or a easy method with which to go forth?
I am definitely keen to avoid the tendancy to make an oven unecessarily big, after all a pizza shouldn't take that long to cook once heated, so cooking one 12" pizza at a time is fine. I actually opt for and prefer the opportunities it brings to enable people to prep, cook & eat together. You will be glad to know I not aiming for world domination here, Though I do appreciate the purist 90 second multi pizza brick oven view/approach too, and aspire to operate at around 450-500C. I have built a cob oven and operated a pompie esque oven before. So experience helps.
How does all that sound to you?
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