#1  
Old 09-09-2011, 04:41 AM
Serf
 
Join Date: Jul 2011
Location: murray bridge south australia
Posts: 22
Default cracks

hello em here from australia i have just finnished building a 50 inch pompeii oven and am very happy with the finnished product. however i did not use a fire blanked but used 4 inches of vermiculite concrete then chicken wire and and more than 1 1/2 inches of concrete.i left oven to cure for about 2 weeks and then followed the 5 step curing fires as recomended in forno bravo plans . however the out side of my dome has cracked quite badly but the inside brick are perfect.i would like to rerender my dome and am thinking of useing a slip layer any advice for me and how to render a slip layer. thanks em
Reply With Quote
  #2  
Old 09-09-2011, 05:23 PM
Neil2's Avatar
Il Pizzaiolo
 
Join Date: Oct 2006
Location: Vancouver Island
Posts: 1,374
Default Re: cracks

"the inside brick are perfect"

This is what counts. Cracks on the outside of the dome are common.

At one time it was advised to have several layers of heavy duty aluminum foil as a slip layer, although this practice seem to have fallen out of favor.
Reply With Quote
  #3  
Old 09-09-2011, 08:44 PM
Serf
 
Join Date: Jul 2011
Location: murray bridge south australia
Posts: 22
Default Re: cracks

thanks neil i am thinking just to rerender over dome with plenty more chicken wire once it has fully dried out there is still plenty of water in the vemiculite
Reply With Quote
  #4  
Old 09-09-2011, 09:38 PM
david s's Avatar
Il Pizzaiolo
 
Join Date: Mar 2007
Location: Townsville, Nth Queensland,Australia
Posts: 4,719
Default Re: cracks

Hi Em,
Because you used vermicrete for your insulation you will have added hundreds of litres of water in the application of this layer (around a third of the volume of vermiculite that you used) To evaporate this much water you need way more than a couple of weeks. Ask yourself how long it would take to boil dry a 44 gallon drum of water. The cracks have occurred because water present in the insulation layer has created steam pressure. Don't be in a hurry to render over the cracks until you are 100% sure the water has been removed.This usually takes about 10 decent firings after the initial curing. If you apply some kind of slip layer, you are also sealing in some of that moisture. I foiled over my vermiculite layer prior to rendering the outside shell. In two places I punctured the foil with quite a few holes and it is in these spots that the oven gets hot on the outside after rainy periods, which is an indication that the vermicrete layer has moisture and steam is finding its way out there.This is a handy indication of what is going on inside but I wouldn't do it again. It slows the drying process too much.
Dave
Reply With Quote
  #5  
Old 09-09-2011, 10:21 PM
Serf
 
Join Date: Jul 2011
Location: murray bridge south australia
Posts: 22
Default Re: cracks

thanks david. yes i agree totaly with you the other thing i did was to render with concrete two days after i rendered the vemiculite, in the middle of winter.traped all the water in .i think i will render over it in a few mouths time by then should have used it over 10 times regards em
Reply With Quote
  #6  
Old 09-09-2011, 11:49 PM
david s's Avatar
Il Pizzaiolo
 
Join Date: Mar 2007
Location: Townsville, Nth Queensland,Australia
Posts: 4,719
Default Re: cracks

Yeah, don't stress over it.The outer shell is only to keep out the weather. But should it rain it would be best to cover it because the rain will enter through the cracks.
Reply With Quote
  #7  
Old 09-10-2011, 12:53 PM
Neil2's Avatar
Il Pizzaiolo
 
Join Date: Oct 2006
Location: Vancouver Island
Posts: 1,374
Default Re: cracks

I also put a vent in the top of the dome thru the stucco and into the vermicrete layer. This is a 1 in dia vent with a rain cap. I also have four 1 inch vents around the perimeter at the bottom of the insulation layer. During firing after a wet spring, I often see steam coming from the top vent.
Reply With Quote
  #8  
Old 09-10-2011, 01:20 PM
david s's Avatar
Il Pizzaiolo
 
Join Date: Mar 2007
Location: Townsville, Nth Queensland,Australia
Posts: 4,719
Default Re: cracks

Quote:
Originally Posted by Neil2 View Post
I also put a vent in the top of the dome thru the stucco and into the vermicrete layer. This is a 1 in dia vent with a rain cap. I also have four 1 inch vents around the perimeter at the bottom of the insulation layer. During firing after a wet spring, I often see steam coming from the top vent.
This is a good idea Neil, I've also incorporated a vent into the insulation space via a system that also supports the flue pipe
Reply With Quote
  #9  
Old 09-11-2011, 02:04 AM
Serf
 
Join Date: Jul 2011
Location: murray bridge south australia
Posts: 22
Default Re: cracks

venting the insulation intresting, but here where i live we only get 13 inches of rain per year here
Reply With Quote
  #10  
Old 09-11-2011, 07:36 AM
david s's Avatar
Il Pizzaiolo
 
Join Date: Mar 2007
Location: Townsville, Nth Queensland,Australia
Posts: 4,719
Default Re: cracks

In our wet season we might get that much in one week.
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
Long Cracks vernod Firing Your Oven 2 04-21-2012 10:43 AM
Question about cracks cholme Firing Your Oven 18 08-05-2011 11:35 PM
When are cracks acceptable? Microheli Newbie Forum 11 07-25-2011 02:26 AM
HELP - Cracks in Dome nodison Australia 10 01-11-2011 02:35 PM
New Fire Bricks with Cracks staestc Getting Started 8 11-03-2008 04:37 AM


All times are GMT -7. The time now is 10:57 PM.

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