Cracks

[gt7761]

I started building small fires in the oven , starting at 50c then increasing each day by 50c , today at one time it reached 200c then around 160c ,( 4th fire), I have noticed a couple of cracks in the dome , one a long one, I still have the blanket to wrap around dome and final render and paint,
my question is are cracks normal..

Greg

[oasiscdm]

Re: Cracks

HI Greg

Would need more information from you eg.
Do you have any straight line joins i.e. where you didn't maintain the brick bond like you see when houses are built.

Also you are curing your oven without blanket which allows the oven to heat at varying temperatures possibly causing it to crack.

You haven't mentioned if there is a vermicrete layer, I'm guessing there isn't.

Some pictures would assist all the experts on here to offer up their comments.

Cracks are normal stated on this site a lot.... So expect them.

I have no cracks at all but took a bloody long time putting my oven together, I took time to ensure I remained on bond, applied my shiralite layer over the dome to lock it in place and also applied my blanket over this b4 cranking it up.

This was done so that the oven heated up evenly and I took my time increasing the temperature, I didn't just cure the oven I also tempered my oven by applying varying heatup temperatures and time short and long fast and slow and steady fires at varying temps.

This was done over a month over this time I had the oven going for a week straight then let it completely go cold then fired it hard then dropped it back. this is how I tempered the oven.

Worse that happened was, was what little mortar was visible inside the oven fell out, because my bond was brick to brick, from front to back bricks needed very little mortar, but I expected this to occur.

[oasiscdm]

Re: Cracks

also I love Porepunkah and Bright my favouriite destination in Victoria. A magical place and visited there every years for years.

[BOOMERS WFO]

Re: Cracks

I would suggest putting the blanket and vermiculite layer on which will assist the cure.

Craig

[gt7761]

Re: Cracks

Thanks for the reply's , I had the idea that I should start with small fires without blanket and final render , as they would trap moisture in , I must be wrong , should I have some sort or hole?vent in the top coat and blanket to let moisture escape.
We have lots of cold weather and damp days this time of year, 2 degrees out side at the moment.
Thanks again.

Greg

[oasiscdm]

Re: Cracks

Don't put render coat on before you cure

[gt7761]

Re: Cracks

sorry but what do you mean

Don't put tender cost on before you cure

[gt7761]

Re: Cracks

so should continue with a few more small fire running all day then blanket and final render.

Greg

[oasiscdm]

Re: Cracks

sorry but what do you mean

Don't put tender cost on before you cure

Yes David was correct typed it on my phone. But I fixed the post to correct spelling.

Personally [and everyone has a different view] you have not mentioned a vermiculate cement insulation layer at all. Is your intention to simply wrap with blanket then your render top coat.?

If so how many layers of blanket will you use. If you intend using a vermiculate layer it is going to saturate the blanket and you will need to rid the oven of that moisture. I would wrap it up and continue the cure.

Unless I am missing something, I think we need more information.....

[gt7761]

Re: Cracks

Thanks Colin,
I have a blanket , two layers or maybe a bit more and render to do, I wasn't going to do vermiculate cement ,I have followed advice from refactory brick supplier , used there bricks,cement and fireclay.
I will try and post some photos later.

Greg

[oasiscdm]

Re: Cracks

I didn't use vermicrete layer, for the same reason as you have stated but as I said I did lock my dome with a 40mm layer of shiralite which insulates and adds a little mass. I started my cure as I applied this layer. I also found the external temperature of the shiralite layer was substantially lower then the external surface of the dome once fired.

I used the shiralite and 2 layers of blanket all over and a third layer of blanket [what I had left] on the top half of my dome.

Although I haven't yet finished my rendering and sealing layer the external temperature of the render as it is at present is at it's hottest 50c with internal oven temp of 450c.