Sue Leabu on tue 6 jul 04
Hello to the carbon trappers!
Hoping for some thoughts and/or experience. Been having problems with lack
of carbon trapping on shinos recently. What I am getting is a very light
gray, rather muddy looking surface. At first I thought perhaps that it was
a bad glaze mix, so I made up some test batches, but the results were the
same. I then noticed that this new bag is labeled "Light Soda Ash" and it's
a lighter and fluffier than the soda ash that I have been using for the
last 18 months. I have read through the archives looking for more info, and
found some posts that mention "Light" and "Dense" soda ash, but couldn't
find anything specific about the effects on carbon trapping, or if they are
chemically different enough to be the cause of my problem. Firing schedule
has not changed at all from previous firings with the "dense" ash. I have a
small amount of the old ash that I will use to mix tests, so I can put in
some samples of each in the next firing. In the meantime, would appreciate
hearing what anyone might know about this. Thanks much as always!
Sue, Kalamazoo
wayneinkeywest on tue 6 jul 04
Sue:
On the bag (probably listed among the "California panel" list for
ingredients) should be a percentage figure.
Compare it with your "normal" soda ash, and adjust accordingly.
Hope that helps,
Wayne Seidl
Key West, Florida, USA
North America, Terra
Latitude 81.45W, Longitude 24.33N
Elevation 3.1 feet (1m)
----- Original Message -----
From: "Sue Leabu"
To:
Sent: Tuesday, July 06, 2004 4:49 PM
Subject: "Light" Soda Ash & Carbon Trap Shino
> Hello to the carbon trappers!
>
> Hoping for some thoughts and/or experience. Been having problems
with lack
> of carbon trapping on shinos recently. What I am getting is a very
light
> gray, rather muddy looking surface. At first I thought perhaps
that it was
> a bad glaze mix, so I made up some test batches, but the results
were the
> same. I then noticed that this new bag is labeled "Light Soda Ash"
and it's
> a lighter and fluffier than the soda ash that I have been using
for the
> last 18 months. I have read through the archives looking for more
info, and
> found some posts that mention "Light" and "Dense" soda ash, but
couldn't
> find anything specific about the effects on carbon trapping, or if
they are
> chemically different enough to be the cause of my problem. Firing
schedule
> has not changed at all from previous firings with the "dense" ash.
I have a
> small amount of the old ash that I will use to mix tests, so I can
put in
> some samples of each in the next firing. In the meantime, would
appreciate
> hearing what anyone might know about this. Thanks much as always!
>
> Sue, Kalamazoo
>
>
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Sue Leabu on wed 7 jul 04
Wayne,
Thanks for a most excellent idea. Unfortunately, the bag for the original
ash with those details is long gone.
Sue, Kalamazoo
On Tue, 6 Jul 2004, wayneinkeywest wrote:
>Sue:
>On the bag (probably listed among the "California panel" list for
>ingredients) should be a percentage figure.
>Compare it with your "normal" soda ash, and adjust accordingly.
>Hope that helps,
>Wayne Seidl
>Key West, Florida, USA
>North America, Terra
>Latitude 81.45W, Longitude 24.33N
>Elevation 3.1 feet (1m)
Dave Finkelnburg on thu 8 jul 04
Sue,
Light and dense soda ash are both sodium carbonate, Na2CO3. The dense
soda ash is compacted, so it has a higher bulk density. As long as you add
them to your recipe by weight, either should give you the same result,
assuming you get both totally dissolved in your glaze.
I suspect you may need to look elsewhere for the cause of your lack of
carbon trapping. Some possible explanations are:
1. a thinner glaze coat (lower glaze density? higher bisque temperature
making bisque ware less absorbent? bisque ware more moist so it is less
absorbent?)
2. Different drying conditions, specifically less drying time, so less soda
accumulation on the surface.
3. Reduction starting later in the firing. Do you begin reduction by a
cone or thermocouple? The latter can drift, read differently over time.
4. Lack of reduction, not as much carbon to trap--different fuel:air mix,
changed damper position, changed fuel value can be culprits.
5. A change in some other glaze ingredient, especially one bearing fluxes.
I wish you well in speedily solving this problem that must be
frustrating.
Dave Finkelnburg in Idaho, where today's garlic harvest has
protected the studio extremely well against the visit of any vampires!
----- Original Message -----
From: "Sue Leabu"
Sent: Tuesday, July 06, 2004 2:49 PM
Been having problems with lack
> of carbon trapping on shinos recently. What I am getting is a very light
> gray, rather muddy looking surface. At first I thought perhaps that it was
> a bad glaze mix, so I made up some test batches, but the results were the
> same. I then noticed that this new bag is labeled "Light Soda Ash" and
it's
> a lighter and fluffier than the soda ash that I have been using for the
> last 18 months.
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