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Fudugazi 06-18-2006 04:00 PM

Refractory Mortar Question
Im using a refractory Plastic Fireclay Premixed Mortar for Firebrick Called DEMON Mortar Mix made by Plibrico Purchased in a Pail. This stuff seems to take quite a while to set up and then if exposed to moisture the next few days it seems to take up moisture again and become more pliable Does this stuff require higher than normal summer air temps to fully cure? Anyone familiar with this stuff It was purchased from Alsips in Winnipeg the largest brick and refractory place around Quite expensive about $40.00 a pail . Hope its the right Stuff!!!

DrakeRemoray 06-18-2006 10:47 PM

The DEMON appears to be an "Air Set" mortar. Here is a link to a different refractory air-set mortar that has a little more info on the page This company does not reccomend Air set for outside installations...I ended up buying
and when I ran out, I bought Heat Stop 50 Dry Mix. These were not cheap either...

Probably want to keep it dry as you can, and then once it is enclosed it would stay dry?

james 06-18-2006 11:14 PM

I have heard from builders that some of the wet pre-mixed mortars (in a tub) don't like exposure to moisture, and that you have to be careful in outdoor use. I think you have to be patient and make sure your enclosure is waterproof.

Not to belabor the point, but Refrax from Forno Bravo is made for pizza oven installation. That's its sole goal in life (along with fireplaces). It is a dry premix, works fine outdoors, has a setting agent, and is less expensive than the wet pre-mixed you find in various masonry supply stores. Some refractory mortars take 48-72 hours to cure, but Refrax is 70% set in 70 minutes.

You still have to pay for shipping from California, but it's something to think about.

Alf 06-19-2006 12:54 AM

In a nutshell “air set” mortars are for thin bed high temperature installations. In other words you use a thin bed of mortar between each brick, we use it in the furnaces under the large bread ovens we build as the furnace runs at a very high temperature when firing. If you use thick beds of mortar shrinkage takes place during drying.

Don’t be mislead by the name “Air set”, the mortar only sets when heat is applied, i.e. during firing. Personally I wouldn’t use it for oven construction, its to expensive and wont hold the bricks well until fired.

Use James’s Refrax or a mortar made with lime and fireclay.


CanuckJim 06-19-2006 06:52 AM

Or you could use a brick mortar made from LaFarge Fondue, brick sand and water. Fondue is readily available in Canada, but it's not cheap and not easy to work with. It sets quite quickly but takes a week to cure and you must be very careful with small fires at first to make sure it's absolutely dry.


Alf 06-19-2006 07:21 AM

We use LaFarge Fondue or any high alumina cement for casting furnace caps, oven side springer bricks etc for our large bread ovens. I have also used it to repair oven arches and have built complete oven arches with it. When we are doing a quick Forno Bravo oven installation we use high alumina cement for the island hearth and vermiculite insulation to get things going.

There are two drawbacks with refractory cement mortar, that is, it sets up very fast so trying to build a small oven from brick is difficult as you usually have a lot of cutting and experimenting to do with the bricks. The second problem is that the mortar can really stain the bricks during building so your lovely brick dome is stained black and no amount of firing will clean it off.


TomB 07-14-2006 10:42 AM

I am building a oven now and am having trouble finding fire clay to make the morter. I an in north east Texas. Any ideas?

james 07-14-2006 11:08 AM

I wish you could skip that part, but the fireclay is the part that is heat resistent in your mortar -- so you need it. I am guessing you have called every brick yard and stone supplier in a 60 mile radius.

If worse comes to worse, we can always send you bags of Refrax via UPS Ground.


TomB 07-14-2006 11:34 AM

You are correct. 200 miles. I have bought two pails of the air set however when I returned, the men laying the bricks thinned it with morter and vermiculite!! I suspect it will have to be rebuilt. If I can figure out how, I will include a picture.

Balty Knowles 05-16-2007 08:36 PM

Re: Refractory Mortar Question
1 Attachment(s)
I was unable to get up to Forno Bravo to pick up som Refmix so I got impatient last weekend & set the first couse down using the formula for high temp mortar. 3 sand 1 fire clay, 1 al silicate, 1 lime. It has been 5 days & its still quite soft. I can scratch out the motar with my fingernail.:eek:

Will it set up or should I rip it out? I can think of a few possibilities of what may be wrong

1 The fire clay says clay mortar on the bag. The brick company assured me it was the same thing.
2 The aluminum silicate was full of small lumps approx 20% by volume, I sifted them out before dry mixing
3 I mixed it a little wet because it goes off so fast. It was very difficult to work after about 10 or 15 minutes.
4 I wet sanded the floor within an hour or so of laying the first course, perhaps it got too wet.

Any insight on the proporerties of this mortar could save me a couple hours of grief this weekend.

Any takers?



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