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Post by josephcrawley on Jan 22, 2015 11:35:12 GMT -8
My mass heater is currently mortared with a 3/1 sand clay mix. Every year I have gaps that open up in the first and hottest bell between bricks. Is there a mortar mix others would recommend to address this? 10 : 6 : 2 : 3 – Sand, Fire Clay, Portland cement, and Lime <- this is a mix recommended for brick bread ovens I know the portland will crumble apart anyone tried this?
thanks
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Post by josephcrawley on Jan 22, 2015 12:43:24 GMT -8
Or have anything else to recommend
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Post by pinhead on Jan 22, 2015 14:32:38 GMT -8
Add a generous amount of ash to your mortar.
Unfortunately I can't recommend a ratio, as my clays are invariably going to be much different than yours.
Either Matthewwalker or Donkey have posted their homemade mixes in detail under the Materials section.
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Post by belgiangulch on Jan 23, 2015 6:33:31 GMT -8
Are you using a local sourced clay ? You might try using one of the fire clay's , I've had better luck using a mix with FC & sand at the high heat areas.
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Post by josephcrawley on Jan 23, 2015 8:59:16 GMT -8
Sorry for lack of clarity I was using a pure potters clay sourced from a pottery supply shop. It was some free purge clay so I can't be sure of the clay body formulation but it would be reasonable to call it clay. Has anyone had experience with any other mixes? I'm going to rebuild my stove next year and would like to use something that is less troublesome.
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Post by matthewwalker on Jan 23, 2015 12:21:26 GMT -8
If it's good clay, you might just need more sand. I've had good results with fire clay/sand, you might add flour paste and cow/horse poop to help it stay together.
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Post by josephcrawley on Jan 23, 2015 12:34:35 GMT -8
I have made a crap ton of cob that's not what I'm talking about when I say mortar. I mean the stuff to join fired brick together.
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Post by DCish on Jan 23, 2015 13:53:19 GMT -8
Maybe shop around for clay with less shrinkage. There is incredible variation between clays on this. Kaolin is expensive, but as I recall has low shrinkage. Adding grog (fired, "pre-shrunk" clay, as it were) may also help, though I don't know if it would help any more than adding more sand would.
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Post by erikweaver on Jan 24, 2015 0:24:46 GMT -8
I haven't been using it very long, so I can't speak to its longevity, but I have been pleased with just using straight fire clay in my fire box. I soak the fire brick a few minutes, and add just enough water to the clay to make it like pudding, and smear it one the faces of the fire brick I am joining. The first time I pressed and wiggled the fire brick until I felt brick against brick. It appeared pretty good to me when I tore it apart last week. The second time when I just rebuilt it, I tried a little thicker joint. I won't know until I tear it apart if that was better or not. I recall reading some mason's web site and they talked about the tight jointing on fire brick. 3mm maximum (about 1/8th inch, all the way down to feeling the brick-against-brick contact. With regard to the sand you are using, it is the really fine sand right? As I recall that was important when using sand in the mortar to joint high heat areas. I'm tempted to say I recall reading of mason's who have also mixed in refractory cement, but I don't recall where I read that, so you'd have to try some Internet searching to find discussion about that. My best guess is I read it somewhere on the Masonry Heater Association website: www.mha-net.org/ (or one of the links they provide).
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Post by josephcrawley on Jan 26, 2015 21:02:08 GMT -8
I met a German/Croatian guy who used to build tile stoves and said they used water glass but didn't remember the proportions. Has anyone tried this type of mortar?
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Post by belgiangulch on Jan 27, 2015 5:43:04 GMT -8
In A strong solution, sodium silicate is a very high temp adhesive. I have used it to repair perlite/fireclay before and I attempted to use it as an adhesive to adhere tiles to the bare metal on my barrel, (did not hold ). Adding some to your fireclay could help to hold it together. For mortaring bricks I use only straight fireclay with no sand in a very thin layer. I recently removed a few bricks from the roof of my burn tunnel and the fireclay that fell sounded like glass as it hit the floor. Water glass is readily available in a 40% solution but for your purposes mixing your own stronger solution would be better.
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Post by pinhead on Jan 27, 2015 6:18:09 GMT -8
I'm in the process of building a brick Batch Box and for the mortar, I used a 2:1:some ratio of sand:clay:ash. I mixed the sand/clay so it's a bit runnier than I'd like for mortar, then added hardwood ash (I think it was hedge) to make it stick together better. A little ash goes a long way in turning the mix into a glue.
EDIT: The sand I'm using is extremely fine - probably fine enough to be hourglass sand. I sifted the clay and the sand through a storm door screen, so both mixes are extremely fine.
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Post by josephcrawley on Jan 27, 2015 9:23:25 GMT -8
Part of my mortar problems are wide joints which is due to using old house brick that lacks the uniformity of modern fire brick. It seems pure clay of any denomination would crack during drying under these conditions but you dont know till you try. Next time I'll add ash and try them both. Thanks for the advice
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Post by pinhead on Jan 28, 2015 14:17:10 GMT -8
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Post by josephcrawley on Jan 28, 2015 19:25:50 GMT -8
That's exactly where I found the recipe in the original post. Those bread ovens get pretty hot so maybe it would be good in a stove as well.
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