High Heat Mortar Primer

[RTflorida]

Re: High Heat Mortar Primer

Fire clay is a specific type of clay with the same refractory characteristics as firebricks.
It has an unusually high content of alumina (24% - 40%) and an overal alumina/silica content of 55%-60%.
Although naturally occuring and found all over the world, there is no way for any of us to judge whether the soil around your home contains fireclay. You may simply have "pain in the ass, I can't dig a whole" clay. If you are serious about using materials found around your home, I would research exactly what the characteristics of fireclay are in nature.
The cheapest and easiest solution is to go to a pottery, refractory, or brick supplier. Fireclay is cheap around here, it is $5 for 15 lbs or $15 for 40 lbs, depending on the supplier.

RT

[timo]

Re: High Heat Mortar Primer

I just picked up 4 50# bags of fireclay from Clay Products in Spring Grove, Illinois. They were $11.40 a bag. I plan on using the mix your own method.

I have found many brick yards want to sell you the Heatstop for $74 instead of the 100% fireclay. Could be due to newer construction rules? Anyway, are there any more reports out there from home brewers and their results?

Thanks,

Timo

[Lars]

Re: High Heat Mortar Primer

Timo,

Yes, I have posted many times about my ( I am pretty sure) success with my wonderful mortar recipe -- 3:2:1:1/2 ( Fine Sand, Fire Clay, Portland, Lime) I have started my first curing fires and do not have anything more to report at this time. So far I still REALLY like the mortar I used, but I haven't gotten anywhere near totally up to temperature. It's so hot, it may be a week before I continue with the curing/insulation.

I suspect that the high dollar mortar manufacturers pushed through regulations to force people to buy their stuff. ( just conjecture with no basis in fact that I am aware of)

Great price on that fire clay, by the way. I think I paid $25 for a 90lb. bag, but someone had brought it up special from another state. I am finished and won't be needing much of the 50lb. bag I have left. I have been mixing it into my (regular) brick mortar for a little light brown color.

Lars.

[Mierkmike]

Re: High Heat Mortar Primer

I made up my refractory morter using the 1113 mix. I was later told by another oven builder that the Portland cement will disenagrate at 600 degrees and the bricks will get loose and fall in. Has anybody experienced this?

[karl]

Re: High Heat Mortar Primer

It is not really the mortar which keeps the bricks from falling in. It is the lining up of the bricks in a certain diameter. If all bricks keep their position and there are contact points between each bricks and it's neighbour bricks (in 2D) the rings should not collapse. But often there are certain areas (in particular in the transition between the oven and the opening) where there are voids which have been filled with mortar. If such mortar disintegrate the ring of bricks may collapse.

karl

[timo]

Re: High Heat Mortar Primer

Karl, thanks for that info. I am right at that point of arch opening to dome. The cuts there are pretty time consuming and baffling. I am trying to keep the brick pieces as large as possible, but there are some smaller ones placed in a thicker than normal mortar gap. Be glad when this part has passed.

From many previous posts I have understood that the large gap(the wedge) on the OUTSIDE of the brick is OK because it doesn't receive a straight dose of heat. I have been trying my best to snug the brick edges together so the gaps on the inside are very small.

Would it be acceptable to say that home brew mortar should be at least 1/8th" thick, but not more than 1/2" thick?

[Lars]

Re: High Heat Mortar Primer

MierkMike,

This was the assumption I have made from what I have read. The mortar will, at best, retain it's shape and adhere to the bricks. At worst, it will crumble.

If you never fired the oven, it would stay together a very long time. I was told that the fire clay, when it gets up to 800-1000 deg. F. will become solid and reject moisture. If this is the case, everything should work fine. I plan to test this by curing some mortar and firing it. I am curious myself.

That was the exact reason I made every brick in my dome tapered by 11 degrees in 'horizontal' ( which becomes vertical at the dome top) and when I got up to 8 chains, I arched over the top [left-right and front-back] That way, if the mortar were to completely fail, my bricks would still be very stuck in place!!!

Lars.

[karl]

Re: High Heat Mortar Primer

I do not think I have mentioned this on the forum during my build. I was struggling figuring out how to do the transition dome/opening as well. Most of the advice on the forum was to do the opening arch first and then do the dome rings. I ended up doing it simultanously and with no precutting of bricks. In fact I allowed the bricks to protrude both in the radial and circumferential direction (when necessary) around the transition. As soon as I reache the height when I could do a continous ring (over the opening) I went in and cut off all the protruding bricks and also cut a suitable angeled surface for the next continous ring bricks in the top bricks of the opening arch. It was not very hard to do this cutting and I would recommend the method (clearly above the "mortar fill-in" method and as a time saver for those who consider the "taylor pre-cut" approach).

Karl

[bimbo]

Re: High Heat Mortar Primer

I made up my refractory morter using the 1113 mix. I was later told by another oven builder that the Portland cement will disenagrate at 600 degrees and the bricks will get loose and fall in. Has anybody experienced this?

I'm sure if there was an issue there would be far more upset people on forums like this. You will get the odd crack or 2 but even if alot of the mortar failed what karl said is right it is really the brick pushing on the bricks either side of it wedging it in place

[cecilB]

Re: High Heat Mortar Primer

I have a question about fireclay - there is a place called Brackers in Lawrence, Kansas, - a pottery supply place and they carry fireclay - but some is called 35 mesh, and some is 50 mesh - can anyone explain? Can I use this for the homebrew mix?

Thanks
Cecelia

[Lars]

Re: High Heat Mortar Primer

I used fireclay from Lawrence.
It worked fine as far as I know, but I DO notice the bricks, when you tap on them ( and I don't do this too hard) seem like they may just be hanging in there...

[cecilB]

Re: High Heat Mortar Primer

Thanks, Lars.
Do you know what the difference is between the meshes? 35 or 50?
And how do they price it? Per ounce or per pound?
I did email them, but maybe I should call them.

Did you mix your fireclay with the portland cement and sand and lime?
If the bricks are cut properly, though, they won't just be hanging, right?

I may just have Capital Concrete order the heatstop50 for me....

Cecelia

[Lars]

Re: High Heat Mortar Primer

Cecelia,
I have posted my 'recipe' and thoughts on it many times, but I used 3:2:1: (1/2) very fine sand, fireclay, portland, and lime. It is a GREAT mortar.

My bricks are all in place, yes,but I guess after you fire a few times, and ALL the moisture is out if them, they really do take on a hollow sound when tapped. I have made pizza 5 or 6 times. ( we made 5 pizzas saturday night). and it's holding together fine.... it's just, my transition from dome to chimney could have been a little more elegant.

Don't be scared off of 'homebrew' mortar from my comments. Heat is very powerful and it is difficult to contain it without some cracking and loosening of the many many pieces making up the dome.

Good luck.

L.
ps. when I do a test of this mortar mix ( mix up , cure, and fire several times) I will let everyone know how it turned out.

[timo]

Re: High Heat Mortar Primer

I just recently completed the dome and curing and used the home brew recipe.

I used 3:1:1:1, sand, fireclay, portland, lime. Seems to acting in a normal manner so far: thin cracks in places, hollow sounding, but snug and secure. For myself using this mix made sense, but the true refractory mortar must harden much harder.

Be sure to mix all the 3:1:1:1, or 1/2, first, before adding water. It's very sticky and should hold bricks almost to vertical (I had to use a form for the last three courses). Also make sure to soak bricks and hydrate and cover

[Dutchoven]

Re: High Heat Mortar Primer

but some is called 35 mesh, and some is 50 mesh - can anyone explain? Can I use this for the homebrew mix?

Thanks
Cecelia

Cecelia
It most likely refers to the mesh size used to sift it. 35 openings per inch or 50 openings per inch. I would suggest the finer clay but, I don't see any reason why you couldn't use either in the homebrew mortar mix.
Best
Dutch