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hard clay/cobalt/blue matt glazes

updated mon 24 jul 00


Ingeborg Foco on fri 21 jul 00


For hard clay, use an old bath towel. Soak it in water and wrap around the
brick of hard clay. Put into a plastic bag and leave for 24 hours. Viola,
soft and useable clay.


Craig Martell on fri 21 jul 00

Debby axed:

>Also bought some cobalt carbonate(?) at a good price, but it is not
>that pinkish color that I am familiar with. Could it be cobalt oxide
>instead? It is brownish tan.


Brownish tan sounds like it could be manganese carbonate. Perhaps it was
mislabeled. Put some in one of your base glazes and fire it to cone
6. Use about 2 or 3 percent. If it produces a treacle brown or a purplish
mauve color it's probably manganese carb. If it's a strong blue it it
likely a cobalt material. Cobalt oxide is black, so I'm suspicious.

Manganese is potentially toxic in the raw state so don't breath the dust or
ingest it in any way. Protect bare skin too.

later, Craig Martell in Oregon

Debby Schwartz on fri 21 jul 00

Hi everyone, I 'm new to the list and really enjoying reading and learning
from all the messages.
I went to CreekTurn Pottery's closeout sale this week after reading the
post about it. I purchased lots of clay half-price. But was it a bargain??
The clay is very hard. I remember some old posts about freezing clay and how
to get it ready for throwing. I tried to find some help in the archives
about wetting hard clay. Could someone refresh my memory, please?
Also bought some cobalt carbonate(?) at a good price, but it is not
that pinkish color that I am familiar with. Could it be cobalt oxide
instead? It is brownish tan. Thanks for the help.
I am on a mission testing cone 6 oxidation blue matte glazes. I am
testing some from the archives, but would appreciate anyone sending me some
reliable recipes that have worked for them. Thank you! Debby in sunny
southern NJ
PS, Anyone from Buffalo, NY on the list that works at the craft center at
UB? I'd like the recipe for the "Laura's Blue" that we used there!

Sharon31 on sat 22 jul 00

Hello Debbie!
This is how I renew dry clay:I sock it in water for a few days. Then, using
an electric drill and a tool , can be of a mixer, I carefully mix it and dry
( as much as I want to) in cloth or in a plaster mold, shaped like a bowl.
About The Cobalt carbonate:
If it is the oxide, you win, it costs more!
On the other hand, it could be from a different mine that is not used these
(I had an old GREY copper oxide!)
Another advise: Do not mix the glazes you make with this "cobalt carbonate"
with other cobalt carbonate. Let it be a new material, at list until you
sure that it is the same one

----- Original Message -----
From: Debby Schwartz
Sent: Saturday, July 22, 2000 12:36
Subject: Hard Clay/cobalt/blue matt glazes

Marvpots@AOL.COM on sun 23 jul 00

Hi Debby from another New Jersey person:
There are a number of ways that have been used successfully to remoisten
clay. The method I use, and like is:
Wet a large bath towel so that it is just a bit dryer than dripping wet.
Wrap your block of clay in the towel; place that bundle in a plastic bag and
seal the bag with a wire tie; leave that package alone for at least 24
hours. After removing all the wrappings the clay should be moist enough to
throw. If it is still too hard, repeat the process for another 24 hours.
Some knowledgable people advise simply placing the whole block of clay, still
inside the plastic bag, in a bucket large enough so that when filled with
water, the clay package is completely covered. Again, after 24 hours, try it
for throwing.
With a little patience, and experimenting, I'm sure you will be able to
remoisten the clay satisfactorally.

Happy soaking!

Marvin Flowerman (