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soda ash in raku

updated fri 31 jan 97


Tadeusz Westawic on mon 20 jan 97

I have an idle question.

I have been using soda ash for several years now to prevent some
unglazed portions of my raku pots from becomming too heavily reduced in
the PFR (getting too black). I just stir a small unmeasured amount in
water and brush or spray it on.

My question is this: Is the soda preventing reduction, or is it
promoting reoxidation?


Also, thanks to those who discussed vinegar as an electrolyte. I had
been using water softener for sigs and for suspensions when I needed
them. The vinegar and a pinch of bentonite produced a very stable
suspension for me.

Tadzu -- The snow is staying only in the shade.

Tom Buck on thu 23 jan 97

TW: Soda ash=Na2CO3 or Na2O.CO2, so when heated the CO2 is freed from
sodium oxide (soda) and leaves the scene. Hence, the raw clay has a
coating of soda on it of varying thickness. So it does what usually
happens in a salt glaze firing, it combines with the alumina/silica of the
body and forms a glaze. However, since you are putting a thin coat here
and there the glaze is hard to detect but it goes down a few molecular
layers and seals off that portion of the body from the ingression of
carbon particles (aka smoke). Very clever of you. Good potting.

Cheers TomB Hamilton ON Canada URL