#11  
Old 12-13-2009, 07:46 PM
Peasant
 
Join Date: Jul 2009
Location: Melbourne Australia
Posts: 39
Default Re: mortar question

I'm not sure if this will help anyone or whether it will benifit your topic.
I'm far from a expert on building Wood ovens but prior to building our wood oven, I done over 100 hours of research. I have noticed that the vast majority of people when using Vermiculite as a insulation foundation, they mix there Vermiculite with Portland cement. This is very wrong when one is trying to make a layer of insulation mix. If you are using Vermiculite it should be mixed with a refractory cement. If used this way then the Vermiculite works just as well as any product on the market but if the Vermiculite is mixed with Portland Cement then it's defeating the full "INSULATING" purpose.

I have called 6 suppliers here in Australia who sell both Vermiculite, Perlite and various kinds of refractory cement. 5 of the 6 suppliers were adamant about mixing a refractory cement when using Vermiculite/Perlite when making a base for a wood oven due to its insulated purpose.
I would also like to point out when purchasing Vermiculite here in Australia is a more expensive way of doing it. The best way is to use straight refractory cement it's cheaper and very easy to work with as opposed to Vermiculite but BEST of all it's new technology.

The reason I wanted to add this is because im sure some people will write back saying that the suppliers are saying this just to make more profit but that is NOT the case because if they did want to make more profit then they would push to sell the Vermiculite as it is more expensive here in Australia.

P.s. I noticed someone mentioned using REFMIX and loved it. Why don't you ALL just stick with a refractory mortar like REFMIX in the USA. It's simple to work with just add water and off you go. Is there a great deal of difference in price when purchasing REFMIX as opposed to your 3:1:1:1 mix? It would really need to be a sugnificant price difference between the 3:1:1:1 and the REFMIX for you NOT to choose the REFMIX because it's so much easier to work with and as I mentioned above it's new technology. If the 3:1:1:1 mix is half price then I can understand. I'm just curious.

Cheers
Wheels1974
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  #12  
Old 12-13-2009, 08:12 PM
Tscarborough's Avatar
Il Pizzaiolo
 
Join Date: Oct 2009
Location: Ausitn
Posts: 3,038
Default Re: mortar question

Price will vary by region, but here in Texas you can make an insulating layer (4'x5'x4") for less than 40 bucks retail if you buy the ingredients. Homebrew refractory cement will cost about 10 bucks per cubic foot, so it is way more than 50% cheaper to use ready mix, more like 1/5 of the cost.

The downside, of course is that the quality will vary with the skill of the mixer. It is well worth the extra cost for a typical DIY'er to buy the premix, considering the total cost versus the cost of tearing it out and rebuilding it.

This is something I deal with daily, and trust me, it is worth the extra cost for a homeowner to not have to worry about how to do it or why it works, just add water and lay your fire brick.
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  #13  
Old 12-13-2009, 09:02 PM
Peasant
 
Join Date: Jul 2009
Location: Melbourne Australia
Posts: 39
Smile Re: mortar question

Quote:
Originally Posted by Tscarborough View Post
Price will vary by region, but here in Texas you can make an insulating layer (4'x5'x4") for less than 40 bucks retail if you buy the ingredients. Homebrew refractory cement will cost about 10 bucks per cubic foot, so it is way more than 50% cheaper to use ready mix, more like 1/5 of the cost.

The downside, of course is that the quality will vary with the skill of the mixer. It is well worth the extra cost for a typical DIY'er to buy the premix, considering the total cost versus the cost of tearing it out and rebuilding it.

This is something I deal with daily, and trust me, it is worth the extra cost for a homeowner to not have to worry about how to do it or why it works, just add water and lay your fire brick.
WOW that is a huge saving going the homebrew or (3:1:1:1) or what ever is the correct formular. I can understand why people chose this way. I'm just glad our SHERLITE refractory mortar here in OZ is very well priced.
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  #14  
Old 12-14-2009, 09:50 AM
cynon767's Avatar
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Join Date: Dec 2008
Location: Sacramento, California
Posts: 230
Default Re: mortar question

Quote:
Originally Posted by Wheels1974 View Post
The best way is to use straight refractory cement it's cheaper and very easy to work with as opposed to Vermiculite but BEST of all it's new technology.
The problem is the insulation- straight concrete, whether or not it's refractory, is not insulative. There needs to be something to create airspace. Here in the US, both vermiculite and perlite are relatively inexpensive; mixing them with a binder like cement helps them form a relatively solid subfloor under the hearth. Mixing them with expensive refractory cement might make them a little more temperature-stable, but it would defeat the purpose of using them instead of a more efficient ceramic fiber insulating board... namely, providing a low cost alternative to expensive new materials. They hold up relatively well under compression, and with enough thickness, provide adequate insulation. Really high tech stuff, like castable refractory insulation, is way too cost-prohibitive-- for me, anyway.

If you're willing to spring for the extra cost of refractory materials (as someone else pointed out, somewhere around 5x the price), you might as well use the insulation board instead, and not have to worry about mixing and working with vermicrete or perlicrete.
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Last edited by cynon767; 12-14-2009 at 10:12 AM.
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  #15  
Old 12-14-2009, 06:52 PM
Serf
 
Join Date: Dec 2009
Location: Pompano Beach, FL
Posts: 3
Default Re: mortar question

I mixed up 12 parts fine vermiculite to 2 parts lime, and 1 part (white) portland, and then went over it with a lime stucco. It seems to work just fine, and it flexes, so cracking is minimal and regular. When the dome cools off, everything seals up.
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