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Rockhopper

Member Since 16 Dec 2012
Offline Last Active Sep 29 2016 07:53 PM
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Posts I've Made

In Topic: ^5 On Sitter Bent To 90* - But ^5 On Shelf Barely Started Bending

05 September 2016 - 10:31 AM

Another question:  How important is shelf location in relation to the sitter ?  Should I expect different behavior with a shelf an inch above the sitter, vs having one just below it, and the next one 4-5 inches above ?


In Topic: ^5 On Sitter Bent To 90* - But ^5 On Shelf Barely Started Bending

05 September 2016 - 10:26 AM

I think you should check the temp differences of the mini cone, compared to the self standing cone. It might help you understand the differences.

 

http://www.sheffield...chart_horiz.pdf

 

 

 

best,

Pres

Thanks for the link...  The chart shows the small ^5 as 2230*, and the self-supporting ^5 as 2118-2205, depending on firing rate - which suggests that if the temp was uniform throughout the kiln, the witness cones would have bent before the sitter cone.

 

It makes sense that the sitter cone would need to have a higher melt-point, since it's closer to the elements, and would heat faster than the middle of the shelf - but is it typical for a lightly loaded kiln (pic below) to be that much cooler in the center ? 

 

Obviously, it's going to take more than one firing for me to learn how this kiln behaves.  I guess my main question at this point is:  What happens if I re-fire these pots with a 6 on the sitter ?  Do I have a reasonable chance of good results - or should I start with a fresh batch ?


In Topic: Work Tables

01 July 2016 - 08:43 PM

"Hardieboard" is a fiber-reinforced cement material.  ("Hardie" is actually a brand name - there are similar products from several manufacturers.)

 

There are different types of cement-board - made for underlayment for tile floors & walls, or for exterior use as siding or soffit.  It comes in thicknesses ranging from 1/4" to 1/2", depending on intended use, in sheets from 3' x 5' to 4' x 12'.  If you go with the cement-board, I would recommend using one that's sold for flooring (usually 3'x5').  Regardless of which type/size you get, as nathanhinshaw said, it will have to be evenly supported.