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OscarA 02-15-2011 04:52 PM

air gaps in mortar
I'm at the stage of building the dome and would like to know how air pockets in mortar will affect the oven.
I understand air expands when heated but is it an issue.
I did half of the first chain just mortaring the bricks to the base leaving the wedged part for later only to realise filling in the wedge part (sides) is harder than I thought.
Can I make the mortar runnier than normal so it finds it's way into the smaller gaps easier. I'm using poor mans mortar
3 parts sand
1 part cement
1 part fire clay
1 part lime.

I hope that's the right mix.

Thanks.. Oscar

Les 02-15-2011 05:33 PM

Re: air gaps in mortar
I would try and avoid it. Are you using a grout bag? It requires the mix to be on the thin side but you can squirt it into some pretty small areas. Outside of that, use a pointing tool, but this requires a LOT of time.

OscarA 02-15-2011 05:38 PM

Re: air gaps in mortar
Thanks I look into a grout bag, I was thinking about pinching my wifes icing bag which sounds pretty much along the same lines as a grout bag.

Edit- Just came back from Bunnings (large hardware store in OZ) and they never heard of them so I popped over to the supermarket and got an icing bag which should be a good substitute.
Thanks for the tip Les.


splatgirl 02-15-2011 08:06 PM

Re: air gaps in mortar
A ziplock bag with the corner cut off will work, too. THe freezer kind are sturdier.

Les 02-15-2011 08:09 PM

Re: air gaps in mortar
The icing bag should work. I recall an earlier builder using plastic baggies. Any masonry supply should have a grout bag but you are on the other side of the planet - things spin differently. :)

Edit... Talk about timing. As soon as I posted I saw that Slatgirl had the same suggestion about the plastic bag.

OscarA 02-16-2011 03:37 AM

Re: air gaps in mortar
Thanks Splatgirl and Les, I'll keep the freezer bag/zip bag idea in the memory bank just in case the icing bag breaks or doesn't work as well as I hope.

nandj1966 02-16-2011 05:47 AM

Re: air gaps in mortar
How about inserting a straw, motar then remove. That should allow for the air to escape.

stonylake 02-17-2011 01:01 PM

Re: air gaps in mortar
i got a half a dozen heavy plastic throw away grout bags from the brickyard. i've got to belive that the ziplock would work just as well. buy a hard plastic float to work the mortar in after you fill the gaps...

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