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Raku Firing A Boatload Of Tiles

Raku tiles firing

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#1 Kohaku

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Posted 03 December 2013 - 04:46 PM

I'm working on a couple of tile-inlay projects, and thus looking to firing some 40+ tiles over the next week (most of which are 4*4).

 

I'd like to streamline and improve the process. There are two areas in particular I'd like to tweak...

 

1) Maximizing output from each firing.

 

If I lay the tiles flat, I can get nine tiles on the shelf. I've never tried to use stacked shelves, or fire the tiles on their sides (with support) but I'd consider this if the outcomes would be good. I'd worry that shelves might change the temp gradient or the reduction/oxidation conditions within the kiln, and that side-firing might lead to warping or cracking.

 

2) Efficiently moving the tiles to the post-fire reduction chamber.

 

As of now, I'm scootching each tile to the edge, grabbing it with my tongs, and placing it in the reduction bucket. It's a frustratingly slow process... by the time I get all nine tiles bucketed (three to a chamber) I worry that I've missed out on the best of the reduction effects. Picking the tiles up with my kevlar gloves does not speed things up. I've considered placing the reduction chamber next to the kiln and 'flicking' the tiles into the bucket... but I worry about fracturing.

 

Anyhow, if anyone has grappled with this and has suggestions, I'd love to hear them.

 

7963839.jpg?564

 

 


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#2 neilestrick

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Posted 03 December 2013 - 04:54 PM

I would stand each one up against a kiln shelf post, like books against bookends, then you can grab it by the side without having to slide it to the edge. Stagger them so you don't have to worry about knocking into them as you grab them. You are less likely to get cracking this way, since the tile will heat more evenly than sitting flat on a shelf. Raku clay will not warp, since it's technically an underfired high fire clay. If possible, close the kiln after you grab each one. I built a front loader for this reason. We generally fire a dozen pots at a time, and by keeping the kiln on a bit and closing the door after each pull, the last one is about as hot as the first.


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#3 Kohaku

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Posted 03 December 2013 - 05:06 PM

I would stand each one up against a kiln shelf post, like books against bookends, then you can grab it by the side without having to slide it to the edge. Stagger them so you don't have to worry about knocking into them as you grab them. You are less likely to get cracking this way, since the tile will heat more evenly than sitting flat on a shelf. Raku clay will not warp, since it's technically an underfired high fire clay. If possible, close the kiln after you grab each one. I built a front loader for this reason. We generally fire a dozen pots at a time, and by keeping the kiln on a bit and closing the door after each pull, the last one is about as hot as the first.

 

Cool- I'll give this a go.

 

I don't know about closing the kiln after every grab... but maybe between each chamber closure. I'm also going to try minimal opening on the kiln (it's one of those SPS easy riser models).


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#4 Marcia Selsor

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Posted 03 December 2013 - 05:28 PM

I fire my smaller plaques 8 x 11"in tile setters, the kind where they stand upright leaning back.
My larger slabs I fire upright as well. They are easier to grab that way. Use posts or bricks for them to lean on. I try to make them stand up as straight as possible. No warping.

Marcia

#5 Kohaku

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Posted 03 December 2013 - 05:40 PM

I fire my smaller plaques 8 x 11"in tile setters, the kind where they stand upright leaning back.
 

 

<Makes note for next shopping trip to SPS>

 

Thanks Marcia.


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#6 Benzine

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Posted 03 December 2013 - 08:59 PM

Just spit balling, I have a tile rack in my classroom. It holds several tiles flat, one above another. so in the space of one tile, you get four or five. If a person had a few of these, they could do twenty tiles in the same space as doing four or five.

the down side is that, it would be difficult to pull the tiles out of the rack. Buuuuut, I wonder if the whole rack could be pulled out and put in reduction?

Just an idea...
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#7 neilestrick

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Posted 04 December 2013 - 10:46 AM

the down side is that, it would be difficult to pull the tiles out of the rack. Buuuuut, I wonder if the whole rack could be pulled out and put in reduction?

Just an idea...

 

When we raku fire little stuff, we just load them up onto a soft brick and pull the whole brick. Works great. A tile setter is much heavier, though. But we used to pull large heavy pots out of the kiln with a flat shovel. That may work, especially if you put it up on blocks to make it easier to get the shovel under it. The other benefit of keeping them in the rack is that it will keep the combustible material of the glaze.


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#8 Benzine

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Posted 04 December 2013 - 01:59 PM

 

the down side is that, it would be difficult to pull the tiles out of the rack. Buuuuut, I wonder if the whole rack could be pulled out and put in reduction?

Just an idea...

 

When we raku fire little stuff, we just load them up onto a soft brick and pull the whole brick. Works great. A tile setter is much heavier, though. But we used to pull large heavy pots out of the kiln with a flat shovel. That may work, especially if you put it up on blocks to make it easier to get the shovel under it. The other benefit of keeping them in the rack is that it will keep the combustible material of the glaze.

 

It would be a bit heavy, but I think that one person could lift the entire rack out, with a pair of tongs.  I should note, the one I have in my class is maybe eight inches tall or so, and might be lighter than the others out there.

 

Having another person assisting, would really help in that case too.


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#9 Kohaku

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Posted 04 December 2013 - 02:04 PM

 

the down side is that, it would be difficult to pull the tiles out of the rack. Buuuuut, I wonder if the whole rack could be pulled out and put in reduction?

Just an idea...

 

When we raku fire little stuff, we just load them up onto a soft brick and pull the whole brick. Works great. A tile setter is much heavier, though. But we used to pull large heavy pots out of the kiln with a flat shovel. That may work, especially if you put it up on blocks to make it easier to get the shovel under it. The other benefit of keeping them in the rack is that it will keep the combustible material of the glaze.

 

 

When you did the brick method, did you pull using a tongs?


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#10 neilestrick

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Posted 04 December 2013 - 02:30 PM

 

 

the down side is that, it would be difficult to pull the tiles out of the rack. Buuuuut, I wonder if the whole rack could be pulled out and put in reduction?

Just an idea...

 

When we raku fire little stuff, we just load them up onto a soft brick and pull the whole brick. Works great. A tile setter is much heavier, though. But we used to pull large heavy pots out of the kiln with a flat shovel. That may work, especially if you put it up on blocks to make it easier to get the shovel under it. The other benefit of keeping them in the rack is that it will keep the combustible material of the glaze.

 

 

When you did the brick method, did you pull using a tongs?

 

 

Yes. A soft brick only weighs about 2 pounds. It's perfect for tiny pots and jewelry. For the tile setter, I think one person under it with a shovel and one person on the top with tongs would work well.


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#11 bciskepottery

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Posted 04 December 2013 - 03:02 PM

Don't forget to practice the shovel/tongs routine a couple times before firing . . . best to get the choreography down before actually doing it live/hot. 



#12 neilestrick

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Posted 04 December 2013 - 03:54 PM

Don't forget to practice the shovel/tongs routine a couple times before firing . . . best to get the choreography down before actually doing it live/hot. 

 

That takes all the fun out of it!


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#13 PeterH

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Posted 04 December 2013 - 04:20 PM

I have a vague memory of somebody raku-ing large/awkward pieces by parcelling them up in wire (iron?steel?nichrome?)

with a loop at the top. Might make handling a full tile-rack easier. Regards, Peter



#14 PeterH

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Posted 04 December 2013 - 07:01 PM

Ref for use of wire to handle large pieces http://tinyurl.com/pbg68qo Regards, Peter



#15 Kohaku

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Posted 04 December 2013 - 10:09 PM

Thanks for all the ideas. As you can see (below) I went with Neil's ideas on using posts with the tiles on end. This worked well- I could easily fit 14+ tiles into a run.

 

The kicker is still moving the tiles from the kiln to the reduction chamber. It was easier to grab with the tongs this way... but there was still a significant lag between opening the kiln and getting the last few into reduction.

 

You can see the difference in the three tiles in the image. The larger one (upper right) was popped in and reduced (with a quick burp) almost as soon as the kiln was opened.

 

The tile on the lower right probably had  a couple minutes to cool prior to reduction.

 

My favorite results- incidentally- are the intermediate ones (lower left)... areas of oxidation with point, patterned flashing.

 

Anyhow, people have posted a number of great ideas that I'll need to look into for next time.

 

1480548_262783340535433_2050250355_n.jpg


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#16 Benzine

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Posted 04 December 2013 - 11:12 PM

Great tiles.

 

I see you have a good amount of snow on the ground there.....


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#17 oldlady

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Posted 04 December 2013 - 11:25 PM

nice work!  

 

i am not a raku person but i had a "what if"  moment while reading this thread.  what if you put the reduction stuff right on top of the tiles while they are still on that firing platform and covered it all with an upside down metal can?  only downside i can imagine is that the platform will get very dirty.  refiring the platform will burn off the residue.


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#18 Kohaku

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Posted 04 December 2013 - 11:46 PM

nice work!  

 

i am not a raku person but i had a "what if"  moment while reading this thread.  what if you put the reduction stuff right on top of the tiles while they are still on that firing platform and covered it all with an upside down metal can?  only downside i can imagine is that the platform will get very dirty.  refiring the platform will burn off the residue.

 

I've thought about doing this. There are a couple issues off the top of my head.

 

First- the wares are often as wide (or wider) than the platform.

 

Second (and related)- many kilns (like mine) have a frame that would make in-situ placement of a reduction can pretty awkward

 

The process of adding combustibles would also be a bit more... exciting... when the whole environs (platform, base, wares) was holding at 1400-1600 degrees. I could envisions some near-explosive dynamics taking place.

 

It's definitely something that percolates at the back of my head though...


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#19 oldlady

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Posted 05 December 2013 - 12:24 AM

i attended a raku demo sponsored by highwater clay last winter.  the person doing the demo used such a very simple raku setup that i am surprised every time i see a complicated one.  since i cannot post pictures of what she used and you probably have a phone that lets you call long distance free, my suggestion is to call highwater's florida location and ask the name of the woman who gave the demo.  she is a teacher somewhere in northern florida.

 

her kiln was made of a metal trash can lid with a handle on the top.  this top had holes drilled into the edges which allowed easy attatchment of a cylinder of wire fencing material just inside the lid and hanging down a few feet.  the kiln was actually just a fiber blanket  about 1 inch thick that was attached to the fencing with wired on ceramic buttons.  it weighed only a few pounds and she lifted it straight up off the platform that held the wares using welders gloves.  there was about a 4 inch hole in the side near the bottom for the burner.  the wire fencing is the stuff with 2 inch by 4 inch openings that you probably see in a lot of gardens.  it is substantial enough to support the weight of the lid and just sit on the concrete floor waiting for the next batch of pots.

 

the burner was a weed burner supported by a couple of softbricks  above the level of the kiln floor  and the flame could be adjusted simply by moving the burner closer or farther from the hole in the kiln wall.  the whole thing sat on a platform of softbricks raised above the concrete floor a foot or so and was wide enough to provide a space to warm the next batch while some pots were firing. a few more softbricks held a kiln shelf where the pots were placed for firing.   add a 20 pound  propane bottle and light it up.  this arrangement was so simple that even i could have done it.

 

(wiring a new handle like a pipe across the bottom of the unused part of the original metal trash can would allow two people to lift it to cover up and reduce the pots while still on the platform.)


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#20 neilestrick

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Posted 05 December 2013 - 04:37 PM

I  WIN!

 

But seriously, the tiles are beautiful. I agree that the last one is not as rich as the others, and clearly didn't get reduced as well.

 

I also agree that adding the combustible to the very hot kiln platform could be quite dangerous, even somewhat explosive like you mentioned. Of course, this would all depend on the type of combustible you use. Materials with fine particles like saw dust and such will ignite very quickly and dangerously. But what if you put in a thick stick or small log? It would smolder and smoke quickly, but would not explode, and wouldn't make a big mess. The charred remains could probably be used several times. A thick roll of newspaper might work, too. Anything that doesn't combust too quickly. You could possibly even just put the kiln top back on to contain the reduction, although it may cause everything to cool too slowly. But a large metal trash can could work, too.


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