Snail Scott on tue 21 feb 12
On Feb 21, 2012, at 1:30 PM, Suzanne Storer wrote:
> ...I'd like to remove some black ceramic stain wash on a surface that =3D
is not completely vitrified that's been fired to cone 3. I'm thinking =3D
that some kind of acid carefully applied to these small areas could =3D
lighten or remove the stain by eating it away...
Unfortunately, I don't know of anything that will touch the stain=3D20
(in an engobe or some such?) that won't touch the clay. I'd=3D20
resort to covering it up with a dense clay-colored engobe, plus=3D20
your preferred surface coating if any, and re-firing.
-Snail=3D
Suzanne Storer on tue 21 feb 12
Hi all,
I'm a ceramic sculptor with a piece made of white clay that I want to =3D
alter post firing. If possible I'd prefer not making the changes by not =3D
firing it again. I'd like to remove some black ceramic stain wash on a =3D
surface that is not completely vitrified that's been fired to cone 3. =3D
I'm thinking that some kind of acid carefully applied to these small =3D
areas could lighten or remove the stain by eating it away. At the same =3D
time I don't want to eat away the clay underneath. Muriatic acid didn't =3D
touch it. Suggestions would be appreciated.
Thanks,
Suzanne Storer=3D20
Ogden, Utah
Suzanne Storer on wed 22 feb 12
The stain is black EZ stroke thinned way down with water applied at =3D
bisc. Do you know what might remove the stain while eating away the =3D
clay?
Suzanne Storer
Ogden, Utah
On Feb 21, 2012, at 1:30 PM, Suzanne Storer wrote:
> ...I'd like to remove some black ceramic stain wash on a surface that =3D
is not completely vitrified that's been fired to cone 3. I'm thinking =3D
that some kind of acid carefully applied to these small areas could =3D
lighten or remove the stain by eating it away...
Unfortunately, I don't know of anything that will touch the stain=3D20
(in an engobe or some such?) that won't touch the clay. I'd=3D20
resort to covering it up with a dense clay-colored engobe, plus=3D20
your preferred surface coating if any, and re-firing.
-Snail
Snail Scott on wed 22 feb 12
On Feb 22, 2012, at 9:25 AM, Suzanne Storer wrote:
> The stain is black EZ stroke thinned way down with water applied at =3D
bisc. Do you know what might remove the stain while eating away the =3D
clay?
The black engobe has almost certainly penetrated=3D20
quite thoroughly into the porosity of the bisque, and=3D20
since engobes and glazes are still made of basically=3D20
the same materials as clay (some silica, alumina,=3D20
fluxes and the like, plus oxides - only the ratios differ),=3D20
nothing is going to affect one and not the other. Some=3D20
folks have suggested sandblasting, but this tends to=3D20
pit the surface very easily, and since most coatings,=3D20
both glaze and engobe, are somewhat (or a lot) more=3D20
vitrified than the clay underneath, as soon as the=3D20
coating is removed to expose the clay it bites in a lot=3D20
quicker, causing a terribly mangy surface especially=3D20
if the coating wasn't even or if there is any texture.=3D20
I'd cover it up with a clay-colored engobe, and proceed=3D20
as normal.
-Snail
=3D20=3D
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