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- 18-May 12
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- Mar 20 2013 04:35 PM
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Posted 16 Aug 2012Do I need to use kiln/bat wash on a bat if this is my process: fire my dry greenware pot; paint the pot with underglaze; fire the pot again? I thought maybe the kiln wash on a bat might only be necessary if a pot was covered with glaze, not underglaze. (Low fire clay and underglazes, if that makes a difference.)
If a bat already has kiln wash on it and my pots are only underglazed, never glazed, do I need to sand the bat after the underglaze firings and paint on new kiln wash? I imagine the bat would eventually be covered with lots of rings if I didn't, like coffee mug stains, but is that a bad thing? (Low fire clay and underglazes, if that makes a difference.)
If I wipe the kiln wash on my bat with my hand, a cloud of powder puffs into the air. Is that normal, or did I do something wrong when I mixed it?
Which is harder and less susceptible to chipping: clay with grog or clay without grog? If the answer depends on the clay, then low-fire terracotta clay.
Thanks for your help!
Posted 28 May 2012Hi. I fired underglazed earthenware bisqueware in my kiln to 04 hotness. Unfortunately, after my kiln had cooled and I looked inside, my 04 witness cone had bent only to a clock-angle of 3:30. It should have bent to a clock-angle of 4:00 at minimum, according to Ortonceramic.com.
It typically takes 15 to 25 minutes for a cone to bend, depending upon the cone number. The cone bends slowly at first but once it reaches the halfway point, it bends quickly. When the cone tip reaches a point level with the base, it is considered properly fired; however, the difference between a cone touching the shelf and a cone at the 4 o'clock position is small and rarely affects the fired results.To make sure my kiln heats to 04, should I start using an 03 pyrometric bar under the kiln sitter's actuating rod, like it mentions below (also from Ortonceramic.com)? Is there a downside to that solution?
The Kiln Sitter® shuts off the kiln when a small cone (or bar) placed under the sensing rod receives enough heat for it to fully bend. Bending is caused by the weight of the sensing rod. Because the cone in the Kiln Sitter® is located at the kiln wall (closer to the heating elements), it frequently receives more heat than witness cones, causing the kiln to shut off early. Using the next hotter cone/bar may be necessary.
One more thing: my kiln has no timer, just a kiln sitter, so I can't add extra minutes to a firing. I'm assuming adding extra minutes would solve this sort of problem.
Thanks for any help!
Posted 27 May 2012Hi. I have a few pots that were ruined by dipping them into too-thick clear glaze, matte finish. The glaze pooled in the pot's decorative textures during firing and now the recesses look milky - like the pots were dipped in a watery Elmer's Glue.
The pots were fired again in an attempt to reduce the milkiness, and re-firing did help, but the pots still look terrible.
I like using 04 underglazes. Can I paint underglazes over the milky clear glaze and refire the pots, thus hiding the milky clear coat? Each pot took about a day to fashion and I really want to rescue them.
Or should I refire the pots again and maybe again, and hope the milkiness diminishes enough to the point where the pots look okay?
Is there some other solution better than the ones I mentioned?
Can anything at all be applied over a clear coat? Or is a clear coat the final step in the pottery-making process, like varnish on an oil painting?
Posted 24 May 2012I thought my clay was 06 earthenware. I made some pots, let them dry, painted them with 04 underglaze and fired them at cone 04. The bisqueware pots seem okay and normal.
However, I'm new to firing clay and when I bought the box of clay at a ceramics supply store a couple months ago, I think I may have mistakenly asked for stoneware instead of earthenware. I threw away the box that the clay came in, so I can't check, and now I'm concerned that the clay was stoneware and my pots should've been fired at a much higher temperature, like cone 5.
The pots make the typical "tink" noise when I flick them with my fingernail, if that means anything. And they seem hard like they should be.
Is there a way to tell if my pots have been fired to the proper temperature? If the clay was stoneware, would the pots still be fragile?
I also have several bags of clay that were given to me. They are probably cone 06 earthenware clays, but I don't know; I'm just guessing. The person sometimes used stoneware clay, I recall. Is there a way to check these bags of clay to determine if they are earthenware? Do I make a tiny pinch pot and tap on it kinda hard? What would you do with unknown clay?
Thanks for any responses.
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