Lava?

[asudavew]

Could lava rock be used for insulation?

I was just trying to think of other materials.

Lava rock is light weight and used to make rock wool.

I would sure like to know everyone's opinion!

[nissanneill]

Re: Lava?

Hi Dave,
one very easy way to check this theory out is get a sample and put in your hand with a blow torch aimed into it. You obviously need to be carefull not to burn yourself but it is a wat shown in an add for household insulation here some years ago.
You could set up a simple laboritory test type experiment with thermometers, a heat source and measure the temp rise throughout a sample, say 4 to 6 inch layer. You might also do this with a Vermiculite sample beside it to compare the results.
I would think that the mass of lava rock compared to the air trapped within it would transfer the heat, but I have never tried it.

Neill

[RTflorida]

Re: Lava?

I'm no expert, but the perlite that I used clearly stated on the bags that they were an organic, volcanic (lava?) product.
Thats about all I can add........

[asudavew]

Re: Lava?

Hey everyone!

I bought a 3 dollar bag of lava rock.

It was 1 cubic foot.

I grabbed a 3 inch piece......

held one end..... blow torched the other....
It glowed red on the blow torch side...... It didn't get hot on the other side that I held with my hand.

I'm gonna build a small form tomorrow.... mix some lava rocks and some cement.....

Let it set and I will test again!\

But lava rock is looking really promising and cheap!


Thanks for the responses.

Dave

[JoeT62]

Re: Lava?

WOW. Very interesting. Are you talking about the same stuff they put in the bottom of gas grills?

[asudavew]

Re: Lava?

It was red lava rock from Lowe's....... It came in a bag.. 3 bucks and change.

I'm telling ya.... This is gonna work...

Let me make some samples and I will post results.

It looks very promising.

Dave

[Bacterium]

Re: Lava?

Neill...........that red lava sounds like scoria.....as you know people used it enmass in the 80's as ground cover in their gardens.

[Hendo]

Re: Lava?

people used it enmass in the 80's as ground cover in their gardens.

.... and in their barbecues? I recall practically every BBQ sold once had a 'hot rock' volcanic layer to (I assume) assist with achieving a smokey flavour in food cooked over an open grill. They don't seem to be in favour any more, or has the scoria/volcanic rock all gone?

[asudavew]

Re: Lava?

Yeah that's the stuff.

And no they don't design grills to use it anymore.

I sure think one functions better with it though.

[asudavew]

Re: Lava?

Scoria - Wikipedia, the free encyclopedia

[nissanneill]

Re: Lava?

This could open up a whole host of cheap options for the insulating layers.
I will call past the garden supply and get some samples and do a few tests. Might reduce an oven by Aus$100 or so.

[asudavew]

Re: Lava?

Yeah

That is what I am thinking.

And I'm trying to build on the cheap.... 5 kids at home




Plus I wanted a stronger insulating layer under my dome.

I think this may work, I'm gonna try to build some test blocks tonite.

[maver]

Re: Lava?

I'm not sure the blow torch test is relevant - the time factor with a pizza oven is a bit different. I tried to find comparison K values for lava, the only one I could find with google showed a K value around 2, compared with 0.5 for superisol and about 0.6-0.7 for perlcrete or vermiculite cement. I was unable to verify (tried searching here for the old discussion of K values but could not find it) whether these are the same units. I'd do a bit more background work before moving to a different insulation material - is perlite or vermiculite really that expensive by comparison?

Marc

[asudavew]

Re: Lava?

I found a study that showed the k value of a cement/scoria mixture. Man that took a while.

The study found that k values range from .252 - .174 depending on the ratio of materials.
So I think it looks pretty good.

Here's a link to the study. K values are on page 10 I think.

http://www.academicjournals.org/IJPS...ep/Hossain.pdf

Thanks for the input, I would never would have thought about looking into K values.

[asudavew]

Re: Lava?

Here are some pics of me blow torching a piece of lava rock/scoria (Thanks Bacterium!)

These first few are with the flash on.