Material Options for Oven Floor

I am building the Mattone Barile Grande and need to acquire the material for the oven floor. The castable refractory cement seems preferable to me over a portland/perlite mix just because the drying time is much shorter.
But I am still confused on the exact material I would need to order. My local masonry supply has Heat Stop II. I see a post in these forums that says “DO NOT” use that. I am questing that however. The the store carries Heat Stop II both pre-mixed wet in a pail and dry in a pail (10 lbs). They say dry in a pail is outdoor rated and the exact stuff I would need. The manufacturer’s site says it is dry in a pail.
Another local store has stuff they call Heat Zone. I can find no reference to it online but they say they have it both in a pail and in a bag.
Or I could just order this stuff on Amazon called FireCast Castable Refractory Cement which seems like it is acceptable.
Any input would be greatly appreciated.

Hi Aaron and welcome to the BrickWood forum!

You are talking about the insulating material that fills the “void” in the top slab.

If you want to have castable refractory, that’s fine. The main difference between the so-called “homemade mix” and a castable refractory is the cost. There is also a difference in drying time, although it’s good to keep in mind that the long drying time for the homemade mix refers to Portland cement and Vermiculite. Perlite only takes about 48 hours to cure, because it sheds water (vs. Vermiculite, which retains water).

But yes, you and the supply store are correct. The post from 2018 refers to the pre-mix version of Heat Stop II, which absolutely is not suitable for this project. The dry version, and only the dry version, is fine.

The confusion may come from the fact that they’re both sold in a pail. At the time of that post, I don’t believe the dry version was available. Can’t fault the manufacturer, though…because selling a dry mix in a pail tends to protect it better than in a sack.

Hope this is helpful. and let us know how your project progresses!

Oh, I didn’t realize Perlite was 48 hour curing time. That will probably be my choice then!

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