S. Morris on sat 20 nov 04
I was wondering if anyone knows any differences
between baking soda and soda ash are in a soda
firing??
I realize that baking soda is sodium bicarbonate, and
soda ash is just the sodium ( I think), but I was
wondering if there was any visual difference between
the two. The studio I currently work mixes the two
together uses that in the kiln, but know one can tell
me exactly why?
Any suggestions.
Thanks,
Steph M. , In Normal.
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Fredrick Paget on sun 21 nov 04
> I was wondering if anyone knows any differences
>between baking soda and soda ash are in a soda
>firing??
>I realize that baking soda is sodium bicarbonate, and
>soda ash is just the sodium ( I think), but I was
>wondering if there was any visual difference between
>the two. The studio I currently work mixes the two
>together uses that in the kiln, but know one can tell
>me exactly why?
>Any suggestions.
>
>Thanks,
>Steph M. , In Normal.
>Sodium bicarbonate and soda ash are two closely related chemicals.
>Soda ash is sodium carbonate. Any time you heat sodium bicarbonate
>beyond about 270 deg. C. it gives off a gas (steam and carbon
>dioxide) and breaks down into plain sodium carbonate so if you spray
>it into a hot kiln it instantly turns into sodium carbonate and
>there is no difference inside the kiln from using sodium carbonate
>in the first place.
>
>You can see this for yourself if you heat baking soda in a metal pan
>over a gas stove. When it gets hot enough it starts to break down
>and the powder begins to sort of float in the gas forming a
>"fluidized bed". I performed this experiment when I was a kid and
>was impressed by the strange behavior of the powder which behaves
>more like a liquid. Pity I did not know enough to follow up and
>patent it. About 10 years later the fluidized bed was invented and
>patented using compressed air or gas fed into the bottom of the
>powder bed through a porous floor. It is used in many processes in
>industry from powder coating to gas absorption in environmental
>polution control.
That said, the bicarbonate sold as baking soda in grocery stores is
fine for blowing into the kiln with a vacuum cleaner since it is
light and fluffy compared to soda ash which is coarse and sometimes
lumpy.
If you are going to dissolve it in water and spray it in there is no
difference and soda ash is cheaper.
We used to use baking soda at the college but we switched over to
soda ash sprayed in as a saturated water solution and I see no
difference in the outcome.
Don't spray it onto the pots directly or you get too much on there
and it turns into a matt grey mess.
Fred
--
From Fred Paget, Marin County, California, USA
fredrick@well.com
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