Chris Leake on fri 15 apr 05
I agree with Bruce. I fire to ^09 which is about 1700 degrees and don't lose the burnish. Are you doing your final burnish when the pot is bone dry?
Chris Leake
> ...but even at only 100 degrees they lose their shine.
100 degrees??? Do you mean 1000 degrees?
At 1000 deg C I would definitely expect the burnish to be lost. At 1000 deg
F, the burnish should remain. If you are losing the burnish at 100 deg, then
you didn't actually accomplish any burnishing and all you are seeing is your
crisco evaporating.
Bruce Girrell
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Vince Pitelka on fri 15 apr 05
> does anybody have any experience with burnished and pit fired pieces.
> also, i am trying to achieve a uniform black out of a pit fire. i know
> this will involve reduction but im not sure exactly how to do that. can i
> smother the fire with dirt?
Jessy -
You might be burnishing when the clay is still leather hard, and that
doesn't work very well. The burnished surface is so dense that it has no
capacity for shrinkage, so it crinkles on a microscopic level when the piece
dries. Burnishing really needs to be done when the pot is bone dry, which
means you must add moisture to the surface. You might want to investigate
terra sigs (http://www.digitalfire.ab.ca/cermat/education/274.html). Apply
them to the bone-dry pot, and then polish with a piece of grocery bag
plastic. You can apply multiple layers, but don't overdo it. If you really
do want to burnish, then you do it as soon as the terra sig absorbs, while
it is still damp but not wet to the touch. If it is a larger piece, you
might have to smear a thin coat of glycerin or lard on the pot in order to
burnish the whole thing. If you are relying just on the moisture form the
terra sig, it will dry out before you finish burnishing, and the surface
will start to peel and flake. The glycerin or lard won't evaporate, and
will give you time to finish your burnishing.
It might be difficult to get pure black in a pitfire. You'd be better off
doing it in a bonfire. In order to get black, when the fire has been buring
for a while and is good and hot with plenty of coals, smother the fire with
sawdust, and then immediately bury it completely in dirt, sand, or ashes.
That seals in the smoke, and makes it absorb into the pots. That's what
turns them black. It's referred to as a blackware bonfire.
I bonfire with the wares inside a re-bar (concrete reinforcing bar) "cage"
lined with sheet metal scraps. That at least partially protects the pots
from direct contact with the flames and wood. You can see an image of the
cage after a firing at
http://iweb.tntech.edu/wpitelka/workshops/ancient_clay.htm
Good luck -
- Vince
Vince Pitelka
Appalachian Center for Craft, Tennessee Technological University
Smithville TN 37166, 615/597-6801 x111
vpitelka@dtccom.net, wpitelka@tntech.edu
http://iweb.tntech.edu/wpitelka/
http://www.tntech.edu/craftcenter/
jessy johanneck on fri 15 apr 05
does anybody have any experience with burnished and pit fired pieces. i
have spent countless hours burnishing my pots to a high sheen with some
crisco and a spoon. they look great when i am done burnishing them but as
soon as they go into a kiln or a pit fire they lose all their shine. i
know that burnished pieces will lose their sheen if they are brought to
too high of a temperature but even at only 100 degrees they lose their
shine. does anybody have any suggestions or tips? are pots sometimes
burnished again when they are out of the pit fire.
also, i am trying to achieve a uniform black out of a pit fire. i know
this will involve reduction but im not sure exactly how to do that. can i
smother the fire with dirt??? if anybody has any tips i would love to hear
them. thanks guys.
jessy
Bruce Girrell on fri 15 apr 05
> ...but even at only 100 degrees they lose their shine.
100 degrees??? Do you mean 1000 degrees?
At 1000 deg C I would definitely expect the burnish to be lost. At 1000 deg
F, the burnish should remain. If you are losing the burnish at 100 deg, then
you didn't actually accomplish any burnishing and all you are seeing is your
crisco evaporating.
Bruce Girrell
Rod Wuetherick on sat 16 apr 05
Bruce Girrell said;
> If you are losing the burnish at 100 deg, then
> you didn't actually accomplish any burnishing and all you are seeing is
your
> crisco evaporating.
Thanks for the chuckle ;)
bonnie staffel on sat 16 apr 05
It has been my experience in burnishing/polishing that your pot has to be
extremely dry as well as other pots being bisque fired with it so that no
moisture gathers in the kiln. Touch your pot to your cheek and if it feels
cold, it is still holding moisture. Moisture/steam will take away the
polish very quickly. I would also suggest that you bisque at Cone 010 or
lower. Your Terra Sig is made of what? Or perhaps your clay is not taking
well to the polishing. I have never used any oil to assist in the
burnishing. Perhaps you are getting a false look from that material. Terra
Sig usually almost polishes itself with just a quick rub with a tee shirt or
a piece of soft plastic.
Good luck,
Bonnie Staffel
http://webpages.charter.net/bstaffel/
http://vasefinder.com/bstaffelgallery1.html
Charter Member Potters Council
Cindy in SD on sat 16 apr 05
Dear Jessy,
You don't mention terra sig in your post. I am guessing that you're just
burnishing your throwing body. I have done this--I have made every
mistake in the book. It never worked for me, either. If you're using
terra sig and not getting results, then switch to Vince's terra sig. It
isn't difficult to make. The recipe sounds a little bit complicated, but
it isn't, really, and the equipment isn't expensive. Maybe he'll kick in
with a URL for you--I don't know how to find it on-line, but I know
there are posts in the archives from Vince Pitelka regarding terra
sigilatta. You will like it. It's the best terra sig ever.
Best wishes,
Cindy in SD
Eric Hansen on sun 17 apr 05
as per Santa Clara pueblo or MAria Martinez at San Ildefonso.
Look that up in the library or do it like this:
The instructions if you want to do it the way they do.
Form your pot. Make a red burnishable slip, it goes on
the bone dry pot. Burnish. dry it again. Must single fire
with wood in low flat pit kiln with sheetmetal lid.=20
Smother at full heat (dull red) with ground sheep manure.
Single fire or in other words bisque firing with wood and then
with manure seems to be one of the universals to=20
successful primitive pit fire the Pueblo way. This is
where the strength of the finish seems to come from.
If you have the chance go to Santa Fe. No other pit
fire stuff is like it, especially the stuff done at=20
universities. Bisquing with wood in a pit kiln is kind
of a lost art. It is done at Esalen Art Center too
in Big Sur. Also see Hal Rieggers' book.
E R I C
--=20
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