rmalmgren on fri 9 jun 00
Greetings:
We have been having a problem with glaze flaking with a glaze that I have
used for years. Anyone with thoughts please help me with your suggestions.
The recipe is one that I used at cone 10 for years and lowered to fire at
cone 6 by adding Frit 3134. I use it in my own studio with no problems at
all. But at the community college where I teach we are having these strange
symptoms. Here is the recipe.
Ferguson Yellow (for cone 6 reduction)
Custer feldspar 40
EPK 19
Dolomite 13
Whiting 8
Bone ash 6
Tin oxide 4
Flint 3
Frit 3134 7
Add:
Red iron oxide 0.3
Rutile 0.3
Here are the symptoms and our efforts to solve the problem. When we mix the
glaze it will apply, adhere and fire normally.
After the glazes sits in the bucket for about 10 days when we apply it we
will see cracks in the glaze. They form tiny segments about 1/8" across.
The glaze also chips off easily. It looks remarkably like the Crawl Glaze
that Richard Burkett put on ClayArt some years ago. If we can keep the
glaze from chipping off the final fired work looks normal.
We were pretty sure that at least one of the materials must have been
switched, and we did find that the kaolin was replaced by an unknown
material (labeled kaolin but having no other marking on the bag.) But when
we went back and mixed it with materials straight from the bags, we had the
same problem in a couple of weeks. I should note that all of the brands of
each of the materials are ones that I have used for more than 15 years.
Any thoughts would be very much appreciated.
Rick Malmgren
Lothian, Maryland
rmalmgren@mindspring.com
Louis Katz on sat 10 jun 00
Sounds like a bit of floculation is taking place as something dissolves in the
water. It sounds like our crawling problems down here in the Coastal Bend, where
the water is hard.
As the glaze sits and some materials dissolve its need for water increases and the
shrinkage of the dry coat does also. Try substituting some clacined clay for the
EPK maybe?
Is your water hard?
Louis
rmalmgren wrote:
> Greetings:
>
> We have been having a problem with glaze flaking with a glaze that I have
> used for years. Anyone with thoughts please help me with your suggestions.
>
> The recipe is one that I used at cone 10 for years and lowered to fire at
> cone 6 by adding Frit 3134. I use it in my own studio with no problems at
> all. But at the community college where I teach we are having these strange
> symptoms. Here is the recipe.
>
> Ferguson Yellow (for cone 6 reduction)
>
> Custer feldspar 40
> EPK 19
> Dolomite 13
> Whiting 8
> Bone ash 6
> Tin oxide 4
> Flint 3
> Frit 3134 7
>
> Add:
> Red iron oxide 0.3
> Rutile 0.3
>
> Here are the symptoms and our efforts to solve the problem. When we mix the
> glaze it will apply, adhere and fire normally.
> After the glazes sits in the bucket for about 10 days when we apply it we
> will see cracks in the glaze. They form tiny segments about 1/8" across.
> The glaze also chips off easily. It looks remarkably like the Crawl Glaze
> that Richard Burkett put on ClayArt some years ago. If we can keep the
> glaze from chipping off the final fired work looks normal.
>
> We were pretty sure that at least one of the materials must have been
> switched, and we did find that the kaolin was replaced by an unknown
> material (labeled kaolin but having no other marking on the bag.) But when
> we went back and mixed it with materials straight from the bags, we had the
> same problem in a couple of weeks. I should note that all of the brands of
> each of the materials are ones that I have used for more than 15 years.
>
> Any thoughts would be very much appreciated.
>
> Rick Malmgren
> Lothian, Maryland
> rmalmgren@mindspring.com
>
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