Building a Tandor - Question About Vermaculite

[robtagarth]

Hi All, long time reader, first time poster  

Im building a tandor similar to the one built by Jimmy (Jamie Olivers best buddy) www.channel4.com/programmes/jamie-and-jimmys-friday-night-feast/videos/all/s2-ep1-build-your-own-tandoori-oven

However, Instead of using a metal barrel I'm building an enclosure (this isn't really relevant, but just thrown in for those who are interested) .

My concern is the vermaculite insulation. My parents used to have vermaculite insulation in their extension, but when the house flooded three years ago the insurance people told us that the vermaculite had heavily degraded due to water damage and needed to be replaced. I know NOTHING about this material, but I was under the impression it was a type of stone? If this is the case, I don't understand why it would degrade. 

My worry with the Jamie/Jimmie design is that the vermaculite is open to the elements... if it does degrade then I need to think of another design or another material (is perlite any better?). 

Thanks for the help in advance. 

Namaste:)

Rob

[gracie]

Hi Rob,
I'm not sure of the exact nature of vermiculite...I think it's a mineral which is expanded so has a light texture ( doesn't weigh much). Think popcorn! It is also used in horticulture to hold water and improve soil, so although it may be fine getting wet, if it is wet, its not going to be as effective at insulating.

[oblertone]

Vermiculite is indeed a mined mineral that is then heated to leave a light fluffy material with excellent insulative properties; the popcorn analogy is a very good one with so many similarities that I'm surprised no-one has rendered an oven with popcorn. However, both popcorn and vermiculite will absorb water so leaving it open to the elements is not a good idea.

Many of the tandoor builds are of a temporary nature so water absorption is not a particular issue, if yours is intended to be more permanent then you'll need to find a way of sealing off the insulation layer.

... I'm off to investigate the flame point of popcorn 

[gracie]

Awesome...a popcorn insulated oven. That would smell amazingly!

[cobblerdave]

G'day
diotomite has possibilities. Readily available as its the main component of kitty litter.
The clay shells left behind long dead micro sea animals forms a mass of air spaces that give you an insulation level. It's clay so it should resist heat. Fillers earth or diotomite clays are natural so should be carcinogenic.
Regards dave

[robtagarth]

Thanks for the replies!

Quick question... would perlite be any better? I've also considered making the outer enclosure out of perlite concrete which should provide insulation, and filling the gap between the enclosure and plant pot with pea-gravel (I've seen a few people use gravel in youtube).

Any thoughts?

Thanks!

FYI... the popcorn insulated oven sounds awesome

[cobblerdave]

G'day
Pearlite and Vermiculite are much the same and are interchangeable.
Regards dave