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Perlite or Vermiculite?  RSS feed

 
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Hey everyone!

I have tried to find this information on the internet for a while now, but even engineering and industry sites don't seem to display it. Thought I'd turn to you guys.

Among the goals of my future rocket stove is a really HOT clean burn. So my question is: Which insulation withstands the highest temperature and generally perform best in rocket stove? Exfoliated- Perlite or Vermiculite? They seem to perform rather equal with the exception being the hygroscopic properties.

Thank you!

/Asbjörn in Sweden
 
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Asbjoern Rohde wrote:Among the goals of my future rocket stove is a really HOT clean burn. So my question is: Which insulation withstands the highest temperature and generally perform best in rocket stove? Exfoliated- Perlite or Vermiculite? They seem to perform rather equal with the exception being the hygroscopic properties.


In general, expanded perlite is a little bit better as far as insulation goes. When you use exfoliated vermiculite in a dry state it would be fine as well. In case you want the insulation to be rigid through mixing with clay slip, use perlite, this won't take up as much water as vermiculite.
 
Asbjoern Rohde
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Thank you!

Figured the hugroscopic properties would be irrelevant when used as refractory insulation... but did not take into account the soakage from the clay slip.

Don't suppose anyone know the max temperature perlite and vermiculite can withstand?
 
Peter van den Berg
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Asbjoern Rohde wrote:Don't suppose anyone know the max temperature perlite and vermiculite can withstand?


I've found these figures for perlite:
Maximum usable temperature: 800 C
Sintering temperature: 870 C
Melting point: 1260 C
 
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How does sand compare?
 
Asbjoern Rohde
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bottom of page shows some figures for exfoliated vermiculite

http://www.dupreminerals.com/en/vermiculite/introduction
 
Asbjoern Rohde
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and here are some figures on perlite

http://www.perlite.it/en/what_s_Perlite.asp
 
Mateo Chester
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Lamp workers/glass blowers use vermiculite to allow their art work to cool. These are temperatures that far exceed those generated by any stove. Never have I seen one use perlite. This is from my experience. Hope this helps.
 
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Matt Chester wrote:How does sand compare?


The insulating properties of sand are very poor. Not to be confused with heat retention.
 
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I see there are several uses for Vermiculite and Perlite in insulation and gardening. Is there a differance between the products? Example: Is Vermiculite which is used in fireplaces, insulation and gardening the same product? merinobob
 
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Robert P : Welcome to Permies.com, And a Big Welcome to the Rocket And WoodStove forum threads! Good Question - I take a couple of bites >

We like Perlite and Vermiculite for their individual insulating properties - especially when they can be poured into and fill a cavity. When We must use them and any other material to rigid-ize them,
like when well make a Heat Riser The materials we use - most often a clay slurry - we end up reducing their insulating value ! This is because we fill or partially block their insulating air spaces.

Most people have reported that we use less water building with perlite which is more stable and less subject to failure due to handling and general abrasion both during construction and use, less water
reduces drying times also !

In garden use We are just looking for the ability of ether material to hold water, It is possible that vermiculite has a slight edge initially, however Vermiculite will tend to crumble away -the more the soil
is worked.

Perlite comes in 2 grades, 1 for people to use in gardens and greenhouses and another grade that is hard to find in some regions that is more suited for construction and insulation uses ! Usually the
Perlite for gardening/greenhouse use is clearly labeled on the bags as designated for G/G use !

Tens of thousands of rocket stoves ,and rocket mass heaters have been made from Both materials, often the use of one material over the other was made because only one material or the other was
the one that was locally available or cheaper !

Hope this helps 1 As always your questions and concerns are welcome and solicited! Fo the good of the crafts ! Big AL
 
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I'm also finding perlite a little cheaper and a little more common in gardening stores..
 
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I have a ton vermiculite. So is is safe to say that I can use this to level up the area under the base of the RMH instead of the perlite? We use this mixed up with clay slip when insulating cob floors. Can I use the clay slip with the vermiculite to level my area? The concrete pad was finished incorrectly and is definitely not level. So I'll be using some bricks to make the perimeter and then fill it with 2" of vermiculite/clay slip.

Thanks in advance!
 
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I think vermiculite is more compressible than perlite, so if you want to use it for a loadbearing base, I would add a bit more clay to the mix to stiffen it.
 
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