Dave Finkelnburg on fri 22 sep 00
Martin.
The SO3, which is a product of the oxidation (burning, calcining,
roasting) of sulfur, combines with water to form sulfuric acid whenever the
SO3 can find the water. However, once the kiln is hot enough to burn sulfur
to SO3, even if it finds a water molecule and makes sulfuric acid, it will
be vapor, not liquid, and won't condense to liquid until it cools quite a
bit, which means when the kiln cools or the sulfuric acid goes up the flue.
When the SO3 reacts with water depends only on how long it takes to get
to moisture. In low concentrations it's quite aggressive at grabbing onto
water.
In a gas firing, the SO3 can find some H2O in the kiln. In an electric
kiln, in a dry climate, the SO3 most likely doesn't react until it gets out
the flue. It all depends on your kiln fuel and ambient humidity.
Eventually, it is pretty much all going to come back to earth as sulfuric
acid.
Good question, as usual, Martin!
Dave Finkelnburg
Martin wrote:
>Dewitt has a point when he writes:-
>correctly)
>P2O5 and water forms phosphoric acid.>
>
>When I have kiln full of ware with glaze which includes about 10% Pet Ash,
I
>do need to open the windows and the main doors for a while.
>
>In further experiments I will use that information about SO3 and P2O5 and
>try to see what happens. Is the sulphuric acid going off totally as gas, or
>is it hanging around in the kiln? Do others have views on this?
>
>Martin Howard
>Webb's Cottage Pottery
>Woolpits Road, Great Saling
>BRAINTREE, Essex CM7 5DZ
>England
>martin@webbscottage.co.uk
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