iandol on wed 11 jul 01
Dear Bruce Girrell,
Most probable candidate seems to be from the organic component during =
the ageing stage, that bacterial action which is said to aid plasticity. =
But, before we can be sure we need to know that there is Carbon dioxide =
is in the clay.
I suppose the wrong question to ask is "How do we know that there is Air =
in Clay?". Until the exhaust from the a de-airing pug mill is analysed =
and quantified we just speculate and make assumptions. Then our =
assumptions are called "Facts"
Best regards,
Ivor. Continuing on his inquisitive way.
Des Howard on wed 11 jul 01
Ivor
Another possibility is methane, observed after adding
lucerne (alfalfa) dust to the slip tank,
copious bubbles of gas that flared nicely when lit.
Des
iandol wrote:
> Dear Bruce Girrell,
>
> Most probable candidate seems to be from the organic component during the ageing stage, that bacterial action which is said to aid plasticity. But, before we can be sure we need to know that there is Carbon dioxide is in the clay.
>
> I suppose the wrong question to ask is "How do we know that there is Air in Clay?". Until the exhaust from the a de-airing pug mill is analysed and quantified we just speculate and make assumptions. Then our assumptions are called "Facts"
--
Des & Jan Howard
Lue Pottery
LUE NSW 2850
Australia
Ph/Fax 02 6373 6419
http://www.luepottery.lisp.com.au
Martin Howard on fri 13 jul 01
Harry Fraser of Potclays has responded to this question thus:-
during the processing of clays air is entrained into the slip or blended
powders at various stages. The gases released during de-airing will
therefore overwhelmingly be air. However, there will also be some water
vapour present and possibly minute traces of carbon dioxide or methane
arising from the decay of vegetable matter in the clay. There may also be
a trace of oil vapour. My guess would be that 98% or so of the extracted
gas would be air with water vapour making up a further 1.5-2% and traces
less than 0.01%.
Seija Aalto, of CERAM Testing & Environmental Services will send me their
contribution to the discussion.
Martin Howard
Webb's Cottage Pottery
Woolpits Road, Great Saling
BRAINTREE, Essex CM7 5DZ
England
martin@webbscottage.co.uk
http://www.webbscottage.co.uk
| |
|
