High Heat Mortar Primer

[Gulf]

Natural clay would be just fine to use in the home brew. I can find some very clean layers of it where I live. Some streaks of clay will have rocks and organic matter in it. Clay such as that will need a little processing. That can be a little time consuming but, it can be done.

[mk e]

Right, so if I just use general purpose mortar, will my structure fall down, or will I just lose some of the refractory quality and not get as hot a cook?

That's how mine is built, plain $7/bag mortar, but the inside is pointed with the high heat stuff.

My bother told me that's how he always builds them, it's way easier......but...but.....and after some digging I found this paper that says under 600C it doesn't matter what you use:
https://info.ornl.gov/sites/publicat...es/Pub1043.pdf

only the very surface should ever cross 600C, so normal mortar pointed with heat temp it is.

[Gulf]

Mk e,

It is so much easier to make the home brew and not have to "point" an entire dome imo. Also, I'm going to add part of my reply from the oither thread.

The made from scratch formula (Portland/lime/sand) for general purpose mortar is inadeqate for temps that our ovens reach. It will degrade. But, there is an even worse problem with using premixed masonry cement or premixed mortar. The lime is added for workability in general pupose mortar, not as a refractory. So, here in the states, manufactureres are allowed to substitute part of the lime in the recipe with what the industry calls "or the equivalent". The "equivalent" will usually be crushed limestone and other proprietary additives. This allows the manufactuer to make the product more economically and produce a mortar that is not as caustic. Crushed limestone expands more so than lime when heated. In a fireplace fire box that results in damaged firebrick.

[Pizzahorse]

Natural clay would be just fine to use in the home brew. I can find some very clean layers of it where I live. Some streaks of clay will have rocks and organic matter in it. Clay such as that will need a little processing. That can be a little time consuming but, it can be done.

Thanks, all,

I have a source for clean clay, Sheffield Pottery in MA.

So would I just be losing out on the extra refractory qualities then, do we think?

[UtahBeehiver]

Any brick mason supply store will have dry powdered clay. It is inexpensive, something similar to HC Muddox will work.