Ron Roy on wed 2 nov 05
Has anyone ever had the problem - anyone know how to stop them?
Thanks - RR
ronroy@ca.inter.net (Ron Roy)
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
Paul Herman on wed 2 nov 05
Hi Ron,
I had little white spots in my "Vegas Red" glaze. I suspected they
were little lumps of tin oxide, so I ball milled the glaze for 20
minutes and they went away.
Best wishes,
Paul Herman
Great Basin Pottery
Doyle, California US
http://greatbasinpottery.com
On Nov 2, 2005, at 10:08 AM, Ron Roy wrote:
> Has anyone ever had the problem - anyone know how to stop them?
>
> Thanks - RR
>
> ronroy@ca.inter.net (Ron Roy)
>
dannon rhudy on wed 2 nov 05
Ron, a bit more information? Are they random,
large, small, like freckles, like splotches, what?
And - how often are they occuring? Every piece,
every time, now and again? Every red glaze? A
particular one? Tell me more.
regards
Dannon Rhudy
> Has anyone ever had the problem - anyone know how to stop them?
---
---
John Britt on wed 2 nov 05
Ron,
With such few clues it is difficult to say....but my guess is that they
are pyroxene crystals. They are similar to "tea-dust" crystals in temmoku
glazes, which are caused by magnesium oxide in the low alumina glaze
accompanied by slow cooling.
How much magnesium carbonate/dolomite/talc is in the glaze? Do you have an
extended cooling cycle?
Let me know a bit more,
John Britt
www.johnbrittpottery.com
William & Susan Schran User on thu 3 nov 05
Ron - It is just recently that I've begun working with copper reds again.
Years ago I was very interested in peach bloom glazes, really working to get
that mottled effect. Most of the best effects were simply by aging the
glaze.
So if you're storing the glaze for a period of time, that may be part of it.
In the book "Chinese Stoneware Glazes" by Joseph Grebanier, Watson-Guptill,
1975, the author writes: "All glazes in the general category of oxbloods and
peach blooms must be thoroughly milled. However, since most of them do not
keep well in the wet state, and after a time crystallize in part, it is best
to dry mill them first."
I don't mill my glazes and have not encountered white spots, but I don't mix
large amounts and don't store for long periods any more.
The author also describes the fired glaze having five layers of color:
colorless, then blue, then red, then above that a layer of yellow, then
colorless/greenish - all having to do with the effects of aerial oxygen and
the particle size of copper. So, depending on the evenness of reduction in
the kiln, that might result in white spots (actually clear)
I would assume using black copper oxide instead of copper carbonate might
affect dispersion if the glaze is not milled. This combined with reduction
might lead to spots.
Not an answer, but some things to consider.
-- William "Bill" Schran
Fredericksburg, Virginia
wschran@cox.net
wschran@nvcc.edu
On 11/2/05 1:08 PM, "Ron Roy" wrote:
> Has anyone ever had the problem - anyone know how to stop them?
>
> Thanks - RR
>
> ronroy@ca.inter.net (Ron Roy)
>
> Ron Roy
> RR#4
> 15084 Little Lake Road
> Brighton, Ontario
> Canada
> K0K 1H0
> Phone: 613-475-9544
> Fax: 613-475-3513
>
> ______________________________________________________________________________
> 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.
Bonnie Staffel on thu 3 nov 05
Dear Ron,
Now here is a question that I have found an answer to. When you put
your glazed pots in the kiln, there is still some dampness underneath
and steam is coming through the base glaze as a tiny healed bubble or
some such phenomenon. My high fire majolica work used to have that
problem as I painted oxides, stains and slips on a white base that had
gum in the glaze. When I made sure the pot was dry before firing, I
didn't have that problem any more. All other things remained the same.
Hope this solves your problem.
Regards,
Bonnie Staffel
http://webpages.charter.net/bstaffel/
DVD or Video Throwing with Coils and Slabs
DVD or Video Beginning Processes
Charter Member Potters Council
Ron Roy on sat 5 nov 05
Hi Dannon,
I just recieved a photo - elongated irregular shape - looks like a cloud -
mostly on inside of pots.
This one is inside on a plate jst where the bottom and side meet - shape
follows the horizontal curve of the plate where the side meets the bottom.
I can send a picture if you like - 675 K but I can make it smaller???
Thanks - RR
>Ron, a bit more information? Are they random,
>large, small, like freckles, like splotches, what?
>
>And - how often are they occuring? Every piece,
>every time, now and again? Every red glaze? A
>particular one? Tell me more.
>
>regards
>
>Dannon Rhudy
>
>> Has anyone ever had the problem - anyone know how to stop them?
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
| |
|
