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Cracked Kiln Shelf


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#1 RonSa

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Posted 20 February 2017 - 03:31 PM

I'm getting ready to do a firing soon and decided to check one of the full shelves that I noticed had a hairline crack after the last glaze firing. I lifted it up with the weight of another shelf on top and sure enough it split in two.

 

I have enough shelves and posts so I'm not too worried but looking at the two halves I'm wondering if it could be used as two half shelves (once I clean up any debris from the split.

 

Any thoughts?


Ron


#2 neilestrick

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Posted 20 February 2017 - 03:48 PM

Yes. I use pieces and shards as shelves all the time. If it's a cordierite shelf (yellowish), then you can cut the broken edge with a masonry disc in a circular saw to clean it up.


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#3 RonSa

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Posted 20 February 2017 - 03:55 PM

Excellent, thanks Neil


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#4 Marcia Selsor

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Posted 20 February 2017 - 05:12 PM

Sure. Use it. It will come in handy some day.
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#5 perkolator

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Posted 27 February 2017 - 12:58 PM

Sometimes you just need some "waste shelves" for special instances.  If it doesn't have glaze on it, I keep most broken furniture for some sort of use.  I keep around larger pieces like this as well as small bits (smash shelf with hammer into small pucks for elevating work in kiln, propping, misc).  If you have access to a wetsaw, you can make your broken bits look intentional :)



#6 RonSa

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Posted 27 February 2017 - 01:50 PM

Good idea, thanks. I have a wet tile saw I'll keep this in mind.


Ron


#7 perkolator

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Posted 01 March 2017 - 06:51 PM

Good idea, thanks. I have a wet tile saw I'll keep this in mind.

careful.  I've cut tons of tile in my life working for my dad, a regular tile wet saw is very underpowered to cut kiln shelves, a "brick saw" would be more appropriate and even then that's not really ideal since you're hand feeding it.  a lot has to do with the thickness of the shelves vs blade diameter and the power of the saw motor.  go VERY slowly and let the blade do its thing, or it will grab and suck it in.  clay kiln shelves are significantly easier to cut vs silicon carbide shelves.



#8 RonSa

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Posted 02 March 2017 - 07:46 AM

Thanks for the heads up


Ron


#9 Pres

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Posted 02 March 2017 - 09:15 AM

I just unloaded a load of bowls and patens (plates). I had several shelf pieces in the load as "risers" so that the curve of one bowl would fit the curve of another, or so that one paten rim would not be hitting another. Use of the these broken pieces allows me to get many more glazed pots into the kiln than I would have it I had not used them. I also use broken shelf pieces to make certain that my cone pack is in perfect position to see through the peep hole. I fire with only cones, not kiln setter, so this is extremely important to me, even though temperature color is a pretty good indicator of temperature, cones are more exact.

 

 

best,

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#10 RonSa

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Posted 02 March 2017 - 09:34 AM

I had several shelf pieces in the load as "risers" so that the curve of one bowl would fit the curve of another, or so that one paten rim would not be hitting another. Use of the these broken pieces allows me to get many more glazed pots into the kiln than I would have it I had not used them

 

So let me see if I understand what you are saying.

 

You place a glazed bowl into the kiln, then place a broken piece of shelf in the glazed section of bowl then place another bowl on the broken shelf piece.

 

If so, doesn't that effect the way the glaze fits on the bottom bowl?

Also, won't the broken piece stick to the glaze from the bottom bowl?


Ron


#11 dhPotter

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Posted 02 March 2017 - 09:49 AM

Use an angle grinder. Score both sides of the shelf. Prop the shelf, on the under side along the score line so that on end of the shelf is on the table and the other end is in the air. Lay a piece of scrap plywood or 2x4 along the score line on top of the shelf. Hold the end touching the workbench, firmly. Smack the wood with a hammer. Shelf breaks along the scored line. Will probably take several smacks.



#12 Pres

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Posted 02 March 2017 - 10:34 AM

 

I had several shelf pieces in the load as "risers" so that the curve of one bowl would fit the curve of another, or so that one paten rim would not be hitting another. Use of the these broken pieces allows me to get many more glazed pots into the kiln than I would have it I had not used them

 

So let me see if I understand what you are saying.

 

You place a glazed bowl into the kiln, then place a broken piece of shelf in the glazed section of bowl then place another bowl on the broken shelf piece.

 

If so, doesn't that effect the way the glaze fits on the bottom bowl?

Also, won't the broken piece stick to the glaze from the bottom bowl?

 

Clarification. . . I place a shelf piece under the bowl or paten so that it raises rim of the bowl high enough to not touch the bowl next to it. Sometimes it takes two shelf pieces. I do not place anything in the bowls or patens, everything is underneath the glazed pots. . . I damp clean foot rings so not glaze is on the bottoms, and use a diamond grinder pad to clean/polish the foot rings after firing.


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#13 RonSa

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Posted 02 March 2017 - 04:15 PM

Thanks Pres for clarifying


Ron


#14 perkolator

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Posted 02 March 2017 - 04:24 PM

What he's doing is "staggering" the height of bowl rims, since they're all the same general height - so he can place them closer together and fit more per shelf - very smart way to load.  People who are good at Tetris and puzzles excel at kiln loading!

 

The other method you got confused with actually used to be common in ceramics.  Example:  saggar fired ceramics used to be common when you had "dirty fuel" sources to fire your kiln.  Inside these saggars it was common to stack/cradle glazed bowls inside one another, to maximize your volume.  Since glaze obviously sticks to anything it touches, they would space the bowls apart with 3 small balls of wadding/clay to separate them - the balls would be under the clean foot ring of the top piece and they would clean a circle of glaze where it touched the inside of the bowl underneath - this way nothing sticks to glaze, its all clay-on-clay.  So if you see old Chinese ceramic bowls with 3 unglazed dots in the center, it was likely fired this way and very old.



#15 oldlady

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Posted 02 March 2017 - 04:30 PM

i just happen to have a photo showing one piece on a broken bit of brick that may help clarify.  look at the small piece just about where a 1 would be on a clock.

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#16 RonSa

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Posted 02 March 2017 - 04:32 PM

Thanks for the picture oldlady


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#17 perkolator

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Posted 02 March 2017 - 04:49 PM

That's pretty much it -- but if you took more advantage of this method, you could likely fit several more plates on that shelf level.



#18 RonSa

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Posted 11 March 2017 - 12:27 PM

I just unloaded a load of bowls and patens (plates). I had several shelf pieces in the load as "risers" so that the curve of one bowl would fit the curve of another, or so that one paten rim would not be hitting another. Use of the these broken pieces allows me to get many more glazed pots into the kiln than I would have it I had not used them. I also use broken shelf pieces to make certain that my cone pack is in perfect position to see through the peep hole. I fire with only cones, not kiln setter, so this is extremely important to me, even though temperature color is a pretty good indicator of temperature, cones are more exact.

 

 

best,

Pres

 

 

Thanks, this just idea came in handy


Ron





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