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I fire these vertically.. Not flat on the shelf. They are flat ,no warping usually. largest dimension has been 25"

 

I found myself saying" put your visor back down Marcia' as you approached the kiln after fire stomping!

Have to be a wet day in Oz before I attempt that!

Exciting!.

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Marcia:

If I ever have to slay a dragon I will be calling: you seem to handle fire nicely!

There are some premises that need to be mentioned. Raku clay is much more tolerant of thermal shock, hence it should be able to handle the differential of shelf temp verses air temp. I have to use porcelain, so I have to work within the limits of that body. Secondly, I fire upwards of 100 pieces in my 16CF, I do not have the luxury of loose packing due to price points. So I have found other solutions, one I posted in the "broken platter" thread. Another was meeting Ron in KC in order to formulate my own porcelain body that can handle thermal shock "better", and increase the COE of the body to 6.35 in lieu of the usual 5.25.

The final was to make my own custom setters that stack easily, circulate heat better, and more importantly cool evenly.

 
I fire in bisque vertically, but I do not have the luxury to glaze fire vertically due to glaze run.

Flat Firing

 
Nerd

 

By the way, I am rather fond of Dragons.{Paragon}

 

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Glaze nerd,

hah! My shelf I posted re. Drilling holes in shelf looks similar to yours. I still have some Pemco frit 283 . If I ever finish everything I am doing, maybe I'll go back to crystalline glaze firing. I haven't done any since 1975. Frit should still be good.

Marcia

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HAH-- back at ya... What is the old saying "great minds think alike."  Pemco 283 is gold dust in the crystalline glaze biz. Cerox 506 has also been phased out. I know several who bought hundreds of pounds when they still could. Give up that nasty ole raku and come back to your roots. If Fred Sweet ever shaves his beard I will use if for wadding- looks like it could handle cone 12.

Nerd

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nerd, Fred thinks you should read the crystalline glaze article in the latest PMI.

I am considering giving it a go. I think I have 20or 30 pounds of that old frit.

I will post some of my old crystalline pots. I have one in the Springfield , Illinois State Museum that was

A deep navy blue with electric blue crystals. I had a tiny vile of uranium nitrate.

marcia

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What type of sand did you use? I was advised to use silica sand but find it hard to find? can any sort be used? I have to fire 11 inch earthenware clay wall pockets. I fired a plaque flat on my kiln shelf recently and it cracked right down the middle. I have a small electric automatic kiln. If I buscuit then glaze fire them standing on their edge will that be better or will they warp?

 

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Hi Moon- welcome to the forum.

some pottery supply houses sell "china sand" which will work. Plain river sand will also work. River sand is also used by brick layers, also used in pool filters.  

If the edge is wide enough to support the weight, then  yes.

the other issue is quartz inversion which occurs at 1064F (563C)  when firing large pieces, heavy pieces, or pieces with a lot of shelf contact: slow the firing down to 100F an hour from 1000 to 1100F. Do a forum search as "quartz inversion", I recall that thread from a few years back.

Tom

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You can also use sticks of clay as rollers.  Make them about as thin as a pinkie finger, or extrude them, lay them out like sun rays, and put your plate on that.  Somewhere here there is a whole thread, with pictures (if my memory .........)

 

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As far as the coils I would love a picture of them or a better description how much spacing in between the coils I am assuming sort of like the mosquito coils you light on fire is what I was going to model them after just looking for a better description of the coils if possible thank you

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Hi Brooklin and welcome!

Not like mosquito coils, no. Just thin clay "snakes." Spacing and placement depends on how pyroplastic your clay is, and the shape of the piece you're placing. If your clay warps a lot, you want to use more coils so that the piece is well supported, and doesn't have any spans wide enough to slump into. The idea is to place the coils under the piece so that when the clay goes through quartz inversion and the related expansion and contraction, the piece isn't sticking to the kiln shelf. It also helps large, flat items with rims to heat more evenly because the're not touching the kiln shelf, which behaves as a big heat sink.

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brooklin, look for "grog" in your ceramic supplier's catalog or online.  there are usually several sizes of it available.  it is ground up fired clay and will support your work nicely.  it is a little easier to use than sand because it is bigger than grains of sand.   it is easy to use, just put a shelf into your kiln.  lower a handful of grog to the center of that shelf and spread it out to the size of the piece you plan to fire.   be careful that you do not push grog over the edge of the shelf or it will land on some piece under the shelf and ruin it.   lower the piece and put it down without sliding it around.  leave it alone, finish loading the kiln and fire.

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On 12/11/2019 at 6:24 PM, oldlady said:

brooklin, look for "grog" in your ceramic supplier's catalog or online.  there are usually several sizes of it available.  it is ground up fired clay and will support your work nicely.  it is a little easier to use than sand because it is bigger than grains of sand.   it is easy to use, just put a shelf into your kiln.  lower a handful of grog to the center of that shelf and spread it out to the size of the piece you plan to fire.   be careful that you do not push grog over the edge of the shelf or it will land on some piece under the shelf and ruin it.   lower the piece and put it down without sliding it around.  leave it alone, finish loading the kiln and fire.

Thank you lady! We will look into grog more, my mom was interested in that but coils were easier to make and on hand at the time, but this has sounded like a good route to follow as well. You'll see me here again if I'm having problems with it still, haha XD

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On 12/10/2019 at 1:32 PM, Callie Beller Diesel said:

Hi Brooklin and welcome!

Not like mosquito coils, no. Just thin clay "snakes." Spacing and placement depends on how pyroplastic your clay is, and the shape of the piece you're placing. If your clay warps a lot, you want to use more coils so that the piece is well supported, and doesn't have any spans wide enough to slump into. The idea is to place the coils under the piece so that when the clay goes through quartz inversion and the related expansion and contraction, the piece isn't sticking to the kiln shelf. It also helps large, flat items with rims to heat more evenly because the're not touching the kiln shelf, which behaves as a big heat sink.

Thank you Callie! So would you roll out some clay ropes and wrap the rope around the end of the clay in circles flat on the surface it's on, do you wrap it tight together or leave the 'coils' loose? Should they be bisqued before using them or can you put them under the piece un-bisqued? I've seen people say they reuse theirs so not sure how it all works still there. We fired a bisque load using loosely spiralled coils that had not been bisqued yet, put those under our large flat pieces and they still broke so we know that does not work at least  

Edited by Brooklin

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No, there’s no wrapping of anything. Like Chilly mentions above, arrange the straight clay “logs” in  sun rays or in rows, depending on the shape of the piece on top. I have reused the clay logs, but my clay tolerates that just fine. If you’re concerned, put your green ware platter on top of green ware logs, and fire your bisqued platter on bisqued logs. 

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