It's in the bag

[Neon-Cat]

It's so hot here (Fort Worth, TX), running 103-104 F all last week in the shade at my house, I thought I'd continue to experiment with in-kiln electric reduction -- it is too hot to use the pit fire enclosure.

The pics show spent oak wood charcoal lumps in heavy duty aluminum foil. Nothing is left in the flimsy shells of the foil but ash residue -- easy to vacuum away with the shop vac. I had charcoal on four shelves -- the kiln was clean after firing. Aluminum foil decomposes at 1220 F (660 C, Cone 019-020). Reynolds brand is 98.5% Al with the remainder Si and Fe. The plan worked to some extent but I really need a reducing atmosphere with water vapor at much lower temps during cooling for my lustre glaze. With charcoal wrapped, the foil will not decompose and expose the charcoal until 1220 F plus, giving time for reduction to 1652 F (900 C, Cone 010) and a little on the down-side. It is best to not put the aluminum sacks on pieces -- I did with one and had deposits of metal aluminum. Mostly I have a smoke effect with this firing. Carbon particles are trapped in clay and glazes -- a long session with a propane torch (and various fluxes) last night did not
remove carbonization or the melted aluminum from pieces.

On the piece shown here I also coated the surface surrounding the cat face with jojoba oil before glazing to help keep my glaze where I wanted it. The jojoba oil has a flash point of about 555 F -- here it began to burn-out at 469 F. It smelled real pleasant doing so with no visible smoke from peeps or part-open lid. My kiln is not vented so I typically run most firings with peeps out and lid cracked. I did close up around 1420 F (on the down-side) for this firing.

Stay cool and happy Fourth of July weekend to those celebrating!

Marian
Neon-Cat Ceramics
neon-cat.com

[Ann Brink]

So you had some reduction in your whole kiln, I gather. Have you tried
in-saggar reduction? The saggar could be your heavy duty foil. I tried it a
few times years ago, but my items were small, so I made a clay saggar and
put my items and combustibles inside. It was fun- I should do it again.

Ann Brink, in cool (75 deg.) Lompoc CA (sorry!)

> --
> Photo log at: http://claycraft.blogspot.com/
> You can still send photos to the CLayCraft blog. Ask me for the
> address.
> To unsubscribe send email to Claycraft-...@googlegroups.com
>

--------------------------------------------------------------------------------

-----
No virus found in this message.
Checked by AVG - www.avg.com
Version: 10.0.1388 / Virus Database: 1516/3741 - Release Date: 07/03/11

[Neon-Cat]

Hi Ann -- Yes, back in May I did a series of experimental kitty tiles and saggared them. They were first bisqued then glaze fired to Cone 010 (1652 F, 900 C). Then I put lump oak wood charcoal into foil saggars with the pieces, gave them a few needle holes each to help them kick off, and fired them to 1080 F, well below the point at which foil starts to disintegrate (around 1220 F). I closed up during a slight hold at top. In this piece in the attached pic Mickey (the kitten) was a lovely turquoise (from added copper) on pale orange clay before he went into the saggar. Afterward Mickey did get some metallic copper lustre and the clay body some color. I weighed each charcoal lump as it was put into the foil bags. I found that they lost only 17-27% of their weight during this short low-temperature firing and did not burn as vigorously as expected. Charcoal should begin to burn around and above 716 F or 380 C (never self-igniting below 250 F/121 C).
Charcoal fires can produce heat between 1380-1835 F (750-1000 C) and add to the heat in the kiln when (and if) burning.

Anyway, next time to get better reduction I might try igniting the charcoal first, then loading my foil saggars with the pre-ignited lumps and then running the kiln up to 1150 F or so, and close-up at peak. The other day it was just too hot to play around igniting charcoal fires and messing with live coals.

I got some interesting results the other day and am beginning to like heavily-textured blue cats and other oddities -- perhaps I have started down the decadent road of well-crafted anti-art.

Three cheers to indenpendence -- national and personal!

Marian

--- On Mon, 7/4/11, Ann Brink <anns...@verizon.net> wrote:

[Ann Brink]

Hi Marian,

I'm glad to get the info about temps, and will save your email for when I
try this again, and use foil. In my saggars, I used odds & ends, grasses,
colored paper, copper sulfate, some salt, a banana peel. I remember the
one pot started "sweating" the day after coming out of the kiln. I surmised
it was from too much salt. I washed it and it stopped.

Ann

----- Original Message -----
From: "Neon-Cat" <neo...@flash.net>

Marian

--

Photo log at: http://claycraft.blogspot.com/
You can still send photos to the CLayCraft blog. Ask me for the address.
To unsubscribe send email to Claycraft-...@googlegroups.com

--------------------------------------------------------------------------------

-----
No virus found in this message.
Checked by AVG - www.avg.com

Version: 10.0.1388 / Virus Database: 1516/3744 - Release Date: 07/04/11

[Neon-Cat]

Hi Ann -- I thought maybe that last stuff was more than you might wish to know -- it is good to hear that you might find it useful.

A potter friend and I were chatting the other day about saggar-firing. She'd been to a workshop where they used all kinds of things.
Mostly I have just used the saggars without added chemicals or other goodies -- to achieve reduction for the lustre glaze I am working with in which the oxide colorants are already in the glaze.

When it is cooler again in Texas I will go back to pit firing and try goodies added to foil saggars. I was looking on-line some months ago at some interesting effects a couple of ladies got saggaring cat and dog food in with their pieces -- very colorful! I have both cat and dog food so can throw some crunchies in to try here.

Today is photo and inventory day for me. There is a little guild show-sale this coming weekend and all my work on pieces is done. This morning I have been thinking of all the things I learned these last couple of months. There are a couple of pieces I actually like (including a blue cat) and a bunch of new reproducible glaze effects gleaned that can be used for future work. Two processes for clay bodies, one with coconut fiber, the other with graphite, I'd use again. Both make for strong greenware and strong, low-porosity, low-fired work. After driving myself crazy for months about hanging systems, I now have a handle on mounting methods. Reading a show application yesterday I was a tad dismayed to see that ceramic wall art is not allowed -- bummer, but then again, all I learned can be used in sculpture and for some functional ware.

I had a weeping, salt-crystallizing piece last year -- I washed mine, too, and left it a month to see if it was OK then sealed it. I much prefer using KCl (potassium chloride, a related salt you can get where water treatment and softening products are sold) -- it readily combines with the clay bodies to give a nice thin glaze and doesn't do weird things later.

I hope everyone will have a great day!

Marian