#11  
Old 06-05-2011, 06:41 AM
david s's Avatar
Il Pizzaiolo
 
Join Date: Mar 2007
Location: Townsville, Nth Queensland,Australia
Posts: 4,885
Default Re: Good day from South Oz

Mick,
One little problem that could cause trouble is that a large clay pot will probably have a flat bottom. If this area creates cracks then those pieces won't be self supporting and could fall off the roof of the dome.
There is little difference in price and insulating value between Perlite and vermiculite. Perlite is a slightly better insulator, but for me is slightly more expensive. although they are light materials they still cost ally in freight because they are high in volume. I prefer to use vermiculite because it has less fine dust which is annoying.They are both used in the hydroponic and nursery trade.
Brickies lime is what you want.
Dave
Reply With Quote
  #12  
Old 06-08-2011, 04:33 AM
cobblerdave's Avatar
Il Pizzaiolo
 
Join Date: Jan 2010
Location: brisbane australia
Posts: 2,493
Default Re: Good day from South Oz

Mick
Just a quick though you seen the precast primavera ovens right....made in pieces for transporting. You talked early that you knew a local that had cast an oven....what did he use? is it avaliable local? is it a heatproof casting material.
From what I've read to cast an oven...styro-foam fruit box upside down. mold of damp sand over the top ,shape to suit, cover with thin plastic sheet (cheap plastic painting sheet) to stop sand from sticking. First thin layer of fire proof castable on. Use stainless steel wire (old welding wire) cut to lenghts thickness of castable req and poak into first layer so they give an idea of the thickness. More castable untill the ends of wire disapear. cut out entrance? make on precst entrance? whatever. when castable starts to go off reach the entrance remove first bit of sand and uncover the upturned box.
Break the box and remaining sand falls down and is removed with plastic sheet.
Should produce a shell of even thickness ready for insulating... if you can get some fire proof castable cement that is...
Regards
Cobblerdave
Reply With Quote
  #13  
Old 06-08-2011, 04:54 AM
david s's Avatar
Il Pizzaiolo
 
Join Date: Mar 2007
Location: Townsville, Nth Queensland,Australia
Posts: 4,885
Default Re: Good day from South Oz

If you use the correct amount of water added to the castable mix there will not be any shrinkage, unlike a clay, cob oven which shrinks substantially, so you can simply cover it for 24 hrs and it's cured, then remove the sand, unlike standard concrete it does not need extended wet curing.
Reply With Quote
  #14  
Old 06-08-2011, 05:22 AM
cobblerdave's Avatar
Il Pizzaiolo
 
Join Date: Jan 2010
Location: brisbane australia
Posts: 2,493
Default Re: Good day from South Oz

DavidS
Do you think this method would work? Sorry I know only a little of this and have not investigated it at great depth. I mainly posted to keep the ideas flowing and open up all option....
By the way weres a link to your build? Id love to know how you built an oven in "the Nth" it was hard enough here in the Sth East

Regards Cobblerdave
Reply With Quote
  #15  
Old 06-08-2011, 05:43 AM
david s's Avatar
Il Pizzaiolo
 
Join Date: Mar 2007
Location: Townsville, Nth Queensland,Australia
Posts: 4,885
Default Re: Good day from South Oz

Yes this method will definitely work. If casting a dome in one piece you will get some fine cracks because the dome heats up unevenly ie hotter atvthe top cooler at the base. Something's got to give because of the rapid heat up and resulting expansion. A multiple piece dome is better, but even with some fine cracks the dome won't collapse. I made my mobile oven dome in one piece because I thinkmit's less likelybto shake to bits on the road.I did not create a thread fo my build only bits and pieces. The nth is great fo oven building now because it's the dry season. The wet season is lousy.
Reply With Quote
  #16  
Old 06-08-2011, 08:10 AM
david s's Avatar
Il Pizzaiolo
 
Join Date: Mar 2007
Location: Townsville, Nth Queensland,Australia
Posts: 4,885
Default Re: Good day from South Oz

I advised a guy to try using the home brew mortar recipe as a castable about a year ago and he's quite pleased with the result, but who knows how it will survive the test of time. My guess is that it will not perform as well as a calcium aluminate based castable. One problem is the high proportion of unfired clay in the mix, which will give you some shrinkage problems against the mould. You should remove the sand as soon as the mix is hard enough to be self supporting. This is even more important withba clay/cob oven where the shrinkage is much greater. Another problem is that the mix will take way longer to harden. Cement and lime mixed together create some chemistry that results in very slow hardening. A third problem is the unfired clay content makes slow curing to drive off water even more important to take it slow to avoid cracks and blowing. Good luck.
Dave
Ps I think Shiracete is a calcium aluminate based castable with perlite added to it to make it an insulator. This would not be suitable for an oven because you want a dense material. It is also a waste of money to use it as an insulator for an oven because it is way more refractory than you need on the outside and it's expensive. Unless some of it fell off a truck.

Last edited by david s; 06-08-2011 at 08:28 AM.
Reply With Quote
  #17  
Old 06-15-2011, 08:23 PM
dmun's Avatar
Moderator
 
Join Date: Jul 2005
Location: New Jersey USA
Posts: 4,216
Default Re: Good day from South Oz

Quote:
Does anyone ever have trouble with the oven sinking into the vermicrete layer?
Never happens. Insulating materials have tremendous compressive strength. They build entire houses on top of a foam insulation layer.
__________________
My geodesic oven project:
To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.
,
To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.
Reply With Quote
  #18  
Old 06-17-2011, 05:05 AM
cobblerdave's Avatar
Il Pizzaiolo
 
Join Date: Jan 2010
Location: brisbane australia
Posts: 2,493
Default Re: Good day from South Oz

Dear Mick
Best way to explain it.... put a petite women in a pair of siletos ...8 mm stiletos and get her to stand on the perlite layer. The weight of that women over that 8mm would be the wieght of a bull elephant but only over that 8 mm and of couse it would break through. Put that same petite women in a pair of snow shoes the weights spread out over a larger area so it wouldn't have the same effect.
Trust me ...Do Not Try to use this explaination with you wife... for some reason I know she will not like this... I will not explain any more... just trust me with this one


Regards Cobblerdave
Reply With Quote
  #19  
Old 06-20-2011, 05:46 AM
cobblerdave's Avatar
Il Pizzaiolo
 
Join Date: Jan 2010
Location: brisbane australia
Posts: 2,493
Default Re: Good day from South Oz

Mick

Just saw a copy of Backyard ovens 2 and found something to might be of help regarding pavers. Aparently the top on a lot of them is slightly domed so if you use them on the oven floor its best to use the bottom side up so you have a flatter surface. yes I checked some out at Bunnings and those ones were all a little round on the top surface not much but you wouldn't notice it unless someone told you to look. Also you might consider a double layer to increase the thermal mass most of the pavers were about 50mm (2 in) thick with most bricks being abot 85mm (31/2 in).

Regards Cobblerdave
Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Choosing and finding wood james Firing Your Oven 240 06-10-2014 07:23 PM
Good Morning from Clear Lake, Iowa Thats Hot Introductions 3 03-28-2011 07:50 PM
Can you identify this oven? Argentina? Is it a good newbie oven? jdbizkits Newbie Forum 5 12-17-2009 07:37 PM
Help! Moist Wood In South Florida! tom di Brick Oven Photos 2 01-24-2009 12:59 PM
Is pizza good for you james Pizza 10 07-08-2007 11:35 PM


All times are GMT -7. The time now is 09:03 PM.

Powered by vBulletin® Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Search Engine Friendly URLs by vBSEO 3.6.0
2006/10 Forno Bravo, LLC