Leslie Ihde on sun 23 feb 97
Recently I've developed, or rather returned to, an interest in the look of
unglazed clay. I'm interested in initiating a discussion on the different
ways of handling functional work that isn't glazed. Terra cotta is lovely
unglazed, as are forms made of two colors of clay thrown together. What
have others done when they want the clay's appearance and pure form to
speak for the
piece?
Leslie
Turning Point Pottery Studio
Vestal, NY
Cindy on mon 24 feb 97
Leslie,
I like unglazed clay, too. Most of the unglazed (cone 6 stoneware) things I
make are intended for use as vases, bottles for oil candles, etc. I do
clear glaze the inside of most pieces for a couple of reasons. First, no
matter how vitreous the clay may be, buyers will often not feel assured
that the piece will hold water if it is not glazed inside. Second, the
water in vases tends to get sour if not changed frequently--I don't want my
pots smelling bad and a glazed surface is certainly easier to wash. Third,
I think the clear glazed inside makes an interesting and attractive
contrast to the rougher outer surface.
To decorate my unglazed pieces, I paint on bands of white slip over the
brown body clay. I then incise designs through the white and into the brown
using whatever sgraffito tools come to hand--toothpicks, sticks--you know.
Sometimes, I even use tools made for the purpose. Usually, my designs
are NA inspired. I'd be interested to know what sorts of things you are
doing, too, Leslie.
Cindy
Deb & Curt Maxwell on mon 24 feb 97
Leslie:
I am currently working in low fire (electric kiln) red clay.
I like the unfinished look of it as well. What I can't understand is how the
piece can be functional if it is "unsealed" by glaze (porous). I am working
on some non-functional pieces using glaze or Mayco Stroke and Coat on part of
the surface only . I am using these right on the bone dry clay and once
firing to cone 04. The first lot was fairly successful except in one case
where the color change in the Stroke and Coat was too dark (and ugly). The
'dandelion' color was beautiful as it came out a warm gold color with a orange
undertones to it.
For the bare terra cotta I have tried applying melted beeswax to a warm pot
but it clotted too quickly before it got a chance to "get into" the clay. I
had better success with paste floor wax applied to an oven warmed pot. It
made the color a bit darker with a bit of sheen. After a while the odor of
the wax disappeared too! I just read in Leon Nigrosh's book on Low fire
pottery how ancient potters sealed their pots by either leaving milk to stand
in them a few days (?calcium?) or applied tung oil which permeated the pores
of the pot and solidified. It might be worth looking into the tung oil if I
knew what it was! Of course there's also shoe polish, acrylic sealant etc.
etc. etc.
I still want to try adding stains to clay but that will have to wait. Any
tips from the group would be appreciated.(especially about how unglazed fired
clay can be "functional")
deb clay in warming Calgary
Dannon Rhudy on tue 25 feb 97
----------------------------Original
message----------------------------
It might be worth looking into the tung oil if I
knew what it was!
Deb,
You can get Tung oil at the hardware store; it is used often as
a finish on wood; it goes on as a liquid, but becomes waxen. I
think I read somewhere/time that it is in fact a liquid wax.
Maybe not. Good stuff for wood; don't know how it would function
in constant or prolonged contact with liquids. Certainly it
would not be suitable for food containers.
Perhaps you might consider glazing only the interiors of works
meant for food, liquids, etc;, leaving the exterior part bare
clay.
Dannon Rhudy
potter@koyote.com
George Mackie on tue 25 feb 97
>For the bare terra cotta I have tried applying melted beeswax to a warm pot
>but it clotted too quickly before it got a chance to "get into" the clay. I
>had better success with paste floor wax applied to an oven warmed pot. It
>made the color a bit darker with a bit of sheen. After a while the odor of
>the wax disappeared too! I just read in Leon Nigrosh's book on Low fire
>pottery how ancient potters sealed their pots by either leaving milk to stand
>in them a few days (?calcium?) or applied tung oil which permeated the pores
>of the pot and solidified. It might be worth looking into the tung oil if I
>knew what it was! Of course there's also shoe polish, acrylic sealant etc.
>etc. etc.
>I still want to try adding stains to clay but that will have to wait. Any
>tips from the group would be appreciated.(especially about how unglazed fired
>clay can be "functional")
>deb clay in warming Calgary
>
Deb - there is of course the stuff you can buy in garden shops for sealing
terra cotta flower pots so they dont absorb water and freeze and split in
winter. They are colorless and odorless and relatively inexpensive -
organosilicates I believe. George
Robbie Hunsinger on tue 25 feb 97
I just read in Leon Nigrosh's book on Low fire
pottery how ancient potters sealed their pots by either leaving milk to stand
in them a few days (?calcium?) or applied tung oil which permeated the pores
of the pot and solidified. It might be worth looking into the tung oil if I
knew what it was!
Isn't tung oil toxic? I seem to recall that you're not supposed to seal cutting
Tom Colson on wed 26 feb 97
>I just read in Leon Nigrosh's book on Low fire pottery how ancient >potters sea
Deb-
Tung oil is a standard penetrating oil finish for wood. It orignally
came from a specific plant that contains naturally occuring chemicals
that polymerize (cure) into a water resistant material. The
commercial products of today are the same, except that they usually have
metallic "driers" added to speed curing. You should be able to find it
at any large hardware store in the aisle with the varnish and such.
I've not used it to seal porous ware, but it might work. I wouldn't
use it on ware for food use. The metallic driers are nasty.
Regards,
Tom Colson
tcolson@aimnet.com
Tiles On The Web: http://www.aimnet.com/~tcolson/webtiles.htm
Doug Gray on wed 26 feb 97
Whole Milk will work. It actually can be used to seal up small cracks
in pottery as well. You have to let it stand in the pot for some time
though. It may even need to curdle to actually work as a sealent.
Then, if it is not washed in really hot water, it should seal the
piece nicely.
I've even seen people do this if they plan on painting pottery.
Purely a decorative finish, but the milk seals the clay so that it
doesn't absorb the moisture right out of the brush. It allows for a
more fliud coat of paint to be applied.
Doug Gray
Alpine, TX
Gavin Stairs on wed 26 feb 97
At 06:57 AM 25/02/97 EST, you wrote:
>----------------------------Original message----------------------------
>
> I just read in Leon Nigrosh's book on Low fire
>pottery how ancient potters sealed their pots by either leaving milk to stand
>in them a few days (?calcium?) or applied tung oil which permeated the pores
>of the pot and solidified. It might be worth looking into the tung oil if I
>knew what it was!
....
Milk and blood. That's the old recipe for a paint made of easy to obtain
ingredients... if you happen to be a farmer or a herdsman. The Masai drink
it, I'm told. The active ingredients in both cases are proteins. Albumin
and casein, I think. They clot and plug up the pores. Given a little time
to dry, they become relatively waterproof. You can do similar things by
simply cooking in an earthenware pot. The pores get clogged with organic
gunk that either dries and cures or carbonizes. In either case the pot
becomes water-proof. The modern equivalent (supposing that your taste for
the forgoing is a bit off) is the sort of white carpenter's glue you get for
do-it-yourselfing. There are several varieties, some of which are more
waterproof than others. And then there are the drying oils, like tung,
walnut, linseed and many others. These oxidize slowly in air, forming a
gummy or waxy film, and eventually clotting throughout. Wood workers know
about these things, which have been used for sealing and finishing wood for
centuries. There are many waxes, from bees wax to modern floor waxes. Some
dry, others don't. The more sophisticated of these formulations tend to be
a mixture of waxes and drying oils. Then on the high tech end there is PEG
(polyethelene glycol), which is sort of high-tech wax. It and similar stuff
has been used to stabilize wood, either green or very old archaeological
specimens. Basically, just about anything will seal terra cotta, but you
might not want to drink out of the pot afterwards. None of the above is as
durable nor as dependable as a good vitreous glaze. Most will eventually
wash out, and most are sensitive to temperature (e.g, don't like to get too
hot). Some will affect the strength of the ware, and may eventually lead to
breakage. None of this seems to have bothered our ancestors, who must have
used the first couple of methods at least. On the oher hand, we all seem to
be using high fire ware in our homes now, because we can wash it without
worrying about breakage. We even put it in our dishwashers, which you
certainly can't do with any of the above.
Bye, Gavin
Jonathan Kirkendall on wed 26 feb 97
In a message dated 2/25/97 7:50:21 AM, you wrote:
<knew what it was!>>
Didn't read the original message, but wanted to add that I finish my pit
fired pots with tung oil, and swear by it. An important note, though. DON'T
follow the directions on the can which are for wood. I apply the oil to my
pots with a paint brush, then immediately start wiping with a soft cloth.
Tung oil does not dry the same on pots as on wood, and if you apply it to
pots to let it dry, I have found that it remains tacky. I have not tested to
see if they hold water, but the finish is really exquisite.
Jonathan in Yonkers
Margaret Arial on fri 28 feb 97
Bennett Bean used polyurethane paste which he said came from woodworkers
sources but i was never able to secure any.
Margaret (the night owl )
Eleanora Eden on mon 3 mar 97
Hi all,
Tung oil can be purchased without additives but it takes a long time to
reach hardness, weeks or months, without them. Also it is quite pricy
although a little goes a long way.
Eleanora...back in the chilly north after a week for my daughter's winter
break in the sun and surf...back to 571 Clayart posts...yeegads...BTW I
have a filing system that works great if I can only remember the names of
the files...
Eleanora Eden 802 869-2003
Paradise Hill
Bellows Falls, VT 05101 eden@maple.sover.net
[the address fga@world.std.com is temporary. My mailbox at
eden@maple.sover.net still works -- do not change address books]
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