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Lesson Plans


Santa Clara blackware - long

[ Thread ][ Subject ][ Author ][ Date ]
Dennis Freeman (freemad)
Tue, 07 Dec 1999 08:32:28 -0700

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"One of the Colmans" (Marian) asked about blackware in reference to pit =
firing, so here goes. This is the brief version - there are some =
"tricks" to this, but these are the basics:
1. Use a high-iron clay, preferably one with fine grog in the body. We =
use IMCO Quarry Tile Mix. You can use other clays for the body & then =
rag slip w/ red clay, ala' the Maria video, but this is much more =
difficult. We used to mine & decant our own clay, but I only do this as =
a demo now.
2. Build pots using coil, allow them to dry & sand w/ fine (120) =
sandpaper. Save your sanding dust - you may use it later. If you want =
carved surfaces, do this at leatherhard stage, then dry.
3. Burnishing is done by rubbing water into small areas w/ your finger, =
then burnishing w/ a polished stone. Keep going until entire surface is =
polished. We usually leave the interior unpolished, except for bowls.
4. A second burnish is done by using vegetable oil (Juan Tafoya at San =
Idelfonso swears by chicken grease). Rub the oil in, wait for it to dry =
to a pale haze, then burnish again. This does not yield a satin polish =
- it's more like glass!
5. Decoration can be done with slip applied on the surface ( we use =
yucca leaf brushes ) or by engraving the polished surface w/ a pointed =
tool. Decoration is a whole separate post - my students learn about the =
water / rain / earth symbolism on Pueblo pots.
6. Pre-heat the pots in an oven or kiln the night before you fire to =
reduce thermal shock & drive out any remaining moisture.=20
7. Firing is done in a cut-down 55 gal. drum in the center of the pit, =
w/ a lid. The drum is perforated to allow heat & smoke in, but not =
flame.
8. We fire with juniper wood ( I live in SW Wyo.) because it burns hot, =
is free & doesn't produce sticky creosote. Other woods will work, but =
be sure they are aged & dry. We also stack "cow pies" in the pit =
because they burn hot & clean.
9. Once we have a really hot fire going and the cow pies are mostly =
burnt up, we smother the fire, first w/ dry, powdery horse manure then =
completely cover the pit w/ sawdust. We get the sawdust from the =
woodshop - also free.
10. Wait 3 - 4 hours, then uncover & get the pots out. The results can =
be spectacular! Deep glossy blacks contrast w/ flat decoration. What =
you have done is create a reduction atmosphere in which a lot of carbon =
is available. The iron oxide becomes carbonized - blackware!
11. Warning - the pit will remain hot for days, and if given some =
oxygen, it will start up again. The best thing is to dig it up while =
dousing w/ water. Save the ashes - they can be used to smother future =
fires.
Well, there it is - sorry about the long post, but it's hard to describe =
otherwise. Try it out - if you are really into clay, this is a scream =
and a series of challenging learning tasks for students.

I was asked earlier this week about a web site. Sorry, we don't have =
one yet, but when I return from sabbatical in Jan., it's on the list. =
How can I hope to compete with the sites of others on this list, though? =
=20
Dennis

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"One of the Colmans" (Marian) asked = about blackware=20 in reference to pit firing, so here goes.  This is the brief = version -=20 there are some "tricks" to this, but these are the basics:
1. Use a high-iron clay, preferably one = with fine=20 grog in the body.  We use IMCO Quarry Tile Mix.  You can use = other=20 clays for the body & then rag slip w/ red clay, ala' the Maria = video, but=20 this is much more difficult.  We used to mine & decant = our own=20 clay, but I only do this as a demo now.
2. Build pots using coil, allow them to = dry &=20 sand w/ fine (120) sandpaper.  Save your sanding dust - you may use = it=20 later.  If you want carved surfaces, do this at leatherhard stage, = then=20 dry.
3. Burnishing is done by rubbing water = into small=20 areas w/ your finger, then burnishing w/ a polished stone.  Keep = going=20 until entire surface is polished.  We usually leave the interior=20 unpolished, except for bowls.
4. A second burnish is done by using = vegetable oil=20 (Juan Tafoya at San Idelfonso swears by chicken grease).  Rub the = oil in,=20 wait for it to dry to a pale haze, then burnish again.  This does = not yield=20 a satin polish - it's more like glass!
5. Decoration can be done with slip = applied on the=20 surface ( we use yucca leaf brushes ) or by engraving the polished = surface w/ a=20 pointed tool.  Decoration is a whole separate post - my students = learn=20 about the water / rain / earth symbolism on Pueblo pots.
6. Pre-heat the pots in an oven or kiln = the night=20 before you fire to reduce thermal shock & drive out any remaining = moisture.=20
7. Firing is done in a cut-down 55 gal. = drum in the=20 center of the pit, w/ a lid.  The drum is perforated to allow heat = &=20 smoke in, but not flame.
8. We fire with juniper wood ( I live = in SW Wyo.)=20 because it burns hot, is free & doesn't produce sticky = creosote.  Other=20 woods will work, but be sure they are aged & dry.  We also = stack "cow=20 pies" in the pit because they burn hot & clean.
9. Once we have a really hot fire going = and the cow=20 pies are mostly burnt up, we smother the fire, first w/ dry, powdery = horse=20 manure then completely cover the pit w/ sawdust.  We get the = sawdust from=20 the woodshop - also free.
10. Wait 3 - 4 hours, then uncover = & get the=20 pots out.  The results can be spectacular!  Deep glossy blacks = contrast w/ flat decoration.  What you have done is create a = reduction=20 atmosphere in which a lot of carbon is available.  The iron oxide = becomes=20 carbonized - blackware!
11. Warning - the pit will remain hot = for days, and=20 if given some oxygen, it will start up again.  The best thing is to = dig it=20 up while dousing w/ water.  Save the ashes - they can be used to = smother=20 future fires.
Well, there it is - sorry about the = long post, but=20 it's hard to describe otherwise.  Try it out - if you are really = into clay,=20 this is a scream and a series of challenging learning tasks for=20 students.
 
I was asked earlier this week about a = web=20 site.  Sorry, we don't have one yet, but when I return from = sabbatical in=20 Jan., it's on the list.  How can I hope to compete with the sites = of others=20 on this list, though? 
From big, beautiful & windy = Wyoming,=20
Dennis
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