Rick Monteverde on tue 13 feb 01
Carol -
I've done some limited work with paper clay in low-fire body with
Duncan Cover Coat (CC), not the Amaco Velvets, and have only seen
distinct interference with material containing glazes which have been
applied to greenware. The CC underglazes seem to be porous enough to
pass through any gasses escaping from the paper, but I wonder if the
"velvet" in the Velvets is some sort of glaze-based formula that is
less porous at organic burnout temperature that the Duncan CCs are.
- Rick Monteverde
Honolulu, HI
>Regarding Amaco Velvet Underglazes:
>
>Like Jonathan Kaplan, I recently made some pieces using Velvets under clear
>glaze with very satisfactory results. But one situation had a curious
>result: When I applied the Velvet over an area repaired with paperclay, the
>Velvet underglaze showed some separation (peeling away) from the body after
>my cone 04 bisque firing (porcelain). The area without the paperclay was
>fine. This was most noticeable with the Velvet called "Chartreuse", but it
>was not limited to that color. I am wondering why this happened. Did the
>fiber in the paperclay disturb the interface between the underglaze and the
>clay body when it burned away? If so, would a preliminary bisque firing be
>necessary to first burn out the paperclay before applying underglaze to a
>piece which has paperclay in it? (My paperclay repair mix contains shredded
>toilet paper, porcelain slip and Lana's Magic Water.)
> If anyone has had a similar experience, or has any thoughts on the subject,
>I'm all ears! (Figuratively speaking only, of course.)
>
>Thanks in advance,
>
>Carol, in Indiana
>
>
> on 2/13/01 9:42 Jonathan Kaplan at jdkaplan@CMN.NET wrote:
>
>> We use Amaco Velvet Underglazes as well as Amaco Liquid Underglazes
>(LUGs).
>> We get better glaze coverage and consistency when the underglaze is fired
>onto the piece first.
>
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>
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Carol Sandberg on tue 13 feb 01
Regarding Amaco Velvet Underglazes:
Like Jonathan Kaplan, I recently made some pieces using Velvets under clear
glaze with very satisfactory results. But one situation had a curious
result: When I applied the Velvet over an area repaired with paperclay, the
Velvet underglaze showed some separation (peeling away) from the body after
my cone 04 bisque firing (porcelain). The area without the paperclay was
fine. This was most noticeable with the Velvet called "Chartreuse", but it
was not limited to that color. I am wondering why this happened. Did the
fiber in the paperclay disturb the interface between the underglaze and the
clay body when it burned away? If so, would a preliminary bisque firing be
necessary to first burn out the paperclay before applying underglaze to a
piece which has paperclay in it? (My paperclay repair mix contains shredded
toilet paper, porcelain slip and Lana's Magic Water.)
If anyone has had a similar experience, or has any thoughts on the subject,
I'm all ears! (Figuratively speaking only, of course.)
Thanks in advance,
Carol, in Indiana
on 2/13/01 9:42 Jonathan Kaplan at jdkaplan@CMN.NET wrote:
> We use Amaco Velvet Underglazes as well as Amaco Liquid Underglazes
(LUGs).
> We get better glaze coverage and consistency when the underglaze is fired
onto the piece first.
JoAnn Marion on wed 14 feb 01
Carol,
I have had a similar experience with the Velvet Underglaze. Some of my
high school students have had the medium pink flake off their piece after
bisque firing at ^06. They reapplied the underglaze and refired and the
same thing happened. They reapplied the underglazed, applied clear
glazed, fired at ^05 and it still flaked off! I have no answers and, like
you, would like to hear anyone's thoughts or recommendations for this
problem.
Jo, in Maryland
Stone Ridge School
Bethesda, MD
jmarion@stoneridge.org
Rachael Rice on thu 15 feb 01
If you are using Amaco velvel underglazes you might want to talk to David Gamble at
Amaco. He is very knowledgeable about their products.
Rachael
JoAnn Marion wrote:
> Carol,
>
> I have had a similar experience with the Velvet Underglaze. Some of my
> high school students have had the medium pink flake off their piece after
> bisque firing at ^06. They reapplied the underglaze and refired and the
> same thing happened. They reapplied the underglazed, applied clear
> glazed, fired at ^05 and it still flaked off! I have no answers and, like
> you, would like to hear anyone's thoughts or recommendations for this
> problem.
>
> Jo, in Maryland
> Stone Ridge School
> Bethesda, MD
> jmarion@stoneridge.org
>
> ______________________________________________________________________________
> Send postings to clayart@lsv.ceramics.org
>
> You may look at the archives for the list or change your subscription
> settings from http://www.ceramics.org/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached at melpots@pclink.com.
Jean Cappadonna Nichols on fri 16 feb 01
Jo,
Are your students applying the underglazes to bone dry clay, or slightly
damp? If bone dry, they might try dampening the clay by wiping gently with a
damp (not wet) sponge just before applying the underglaze. Also, if a small
amount of the slip from the clay body is mixed with the underglaze, it may
help it to adhere better. The most common problem causing popping off with
velvet underglazes is too thick an application. While this is an "iffy"
process at best, there can be no more than three coats of any one color or
mixture of colors applied. The problem is identifying what constitutes a
"coat". I have found that if I apply a thinned -down first coat, the process
works more efficiently and does not diminish the color significantly. If you
have access to Clay Times, check out the March/April, 1999, issue. I wrote an
article on this topic.
Best of luck and if you discover any additional info on this subject, pass it
on !
Jean Cappadonna-Nichols
JoAnn Marion on fri 16 feb 01
Jean,
Thanks for your suggestions. My students brushed the underglaze onto a
^04 bisqued piece. They are supposed to wipe down their pots with a damp
sponge before applying glaze or underglaze. Maybe I should try, as you
say, adding a small amount of slip to the underglaze. The thick
application could be the culprit, I never had that problem before but who
knows, the students could have been heavy handed! I will check my Clay
Times of March/April, '99! Thanks for the help!
Thanks, also, to Rachel for the David Gamble of Amaco tip. I took a
workshop from him awhile back, he is helpful. I had thought of calling
him, just hadn't done it but you've convinced me!
Jo, in rainy and gray MD, where's our snow?!
jmarion@stoneridge.org
Cindy Strnad on fri 16 feb 01
Jo,
Sometimes you can get away with applying a thin, but not a thick coat of a
refractory underglaze. I mix frit (3134) and Mason stains, and this works
for me. But if it's applied too thickly, the glaze will crawl.
Cindy Strnad
Earthen Vessels Pottery
RR 1, Box 51
Custer, SD 57730
USA
earthenv@gwtc.net
http://www.earthenvesselssd.com
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