[Stoves] Phosphate bonding of clay and other speculations

[Dean Still]

Dear Crispin,

I think that you might be right...we could run an experiment here, if you
want to design it?

Add phosphate to a brick compare it to a brick without?

All Best,

Dean

-----Original Message-----
From: stoves-bounces at listserv.repp.org
[mailto:stoves-bounces at listserv.repp.org] On Behalf Of Crispin
Pemberton-Pigott
Sent: Tuesday, June 06, 2006 6:32 AM
To: Stoves
Cc: Bruce Berger
Subject: [Stoves] Phosphate bonding of clay and other speculations

Dear Friends

One of the great things about an internet discussion group is that you can
say things that are wa-a-a-y wrong and no one will fire you for it.  Now how
about this idea:

I have been looking at how ceramic stoves are assembled at the microscopic
level and all things considered, I don't think many of the stoves we see are
very 'ceramic' at all.  There are strong phosphate bonds - strong chemical
bonds which are pretty heat resistant.  I am suggesting that several
'traditional' approaches to making clay products are (mostly) phosphate
bonded.

Consider this:  people add cow dung to clay to improve the 'performance'.
It is usually assumed with some degree of support that the reason the clay
lasts longer in a stove is that the holes produced by the fibres make it
into a more flexible and insulative.  Suppose the real reason was that the
phosphates in the dung are creating a stronger product that is not really
held together by melted clay minerals (ceramic bonds) but by chemical ones.

And this: people add a variety of things to clay to make it 'better' and the
secret ingredient may in fact be phosphate, added accidentally, creating a
stronger product.

And this: making 'clay bricks' from ant hill soil (which is full of dried,
fresh grass and biomass, works (makes a decent brick) when the product is
fired at temperatures far too low to be ceramic-bonded.  I suggest it is the
phosphates in the biomass creating a chemical, not ceramic bond.

So....how about we try making 'ceramic' stove parts deliberately salted with
phosphates?  The insulative bricks used in the 6-brick Rocket Stoves could
be made just as easily, but they would be a lot stronger (resist their
inherent nature to disintegrate from thermal shock) if phosphates were
added.

What natural processes form them?  What are the readily available sources of
phosphates?  

Grass
Fertilizer (I was thinking of artificial fertilizer which is widely
available?
Dung
The raw materials for detergents
Phosphoric acid (sounds dangerous)
What about laundry soap?  Omo? Tide?
Bat guano
Chicken 'litter'
Rabbit manure

Instead of using ground charcoal, which has no phosphates at all, how about
using hammer-milled fresh dried grass?  Powdered hay.  Make the porus
structure using something that releases phosphates as it burns.

If there is a lot of phosphate in chicken manure, it could be mixed into the
brick or ring material and when burned, would provide both little air
pockets as well as phosphate bonding.

I suspect that a careful look at the chemistry of traditional ceramics would
repeatedly pitch up natural sources of phosphates that are making chemical
bonds in low temperature clay products like terracotta.  The traditional
'bisquit firing' might just by a slight phosphate bonding, not a very low
temperature ceramic bond.

What's really going on?

Ponderingly yours
Crispin
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