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timbo_heff

Member Since 24 Apr 2012
Offline Last Active Yesterday, 12:51 PM
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#64308 Cone 6 Body Or Cone 6-10 Body: Much Difference?

Posted by timbo_heff on 11 August 2014 - 12:02 PM

 

How does one tell if its cone 6 is under fired , or cone 13 is over fired ?

 

Plot the Apparent Porosity curve and look for the minimum.  It'll be a U shaped curve.  That is the cone that the body is "mature at" and should be the firing cone.  The flatter the bottom of the curve, the more "forgiving" the body will be to firing variations within the kiln as well as for general under or over firing.

 

You also then align this information with a MOR test curve for strength.  You are trying to get the minimum porosity and the maximum MOR to basically overlap on the same cone. 

 

3 percent porosity is a LOT.  Asking for issues in functional tablewares, in work destined for outdoor installations, or things like pool tile, and sinks and such.  Shoot for something below 1%.  The closer to 0 the better in general.  0.5% is a nice optimal target..........hard to hit without dropping the MOR.

 

best,

 

....................john  

 

 

 

How does one tell if its cone 6 is under fired , or cone 13 is over fired ?

 

Plot the Apparent Porosity curve and look for the minimum.  It'll be a U shaped curve.  That is the cone that the body is "mature at" and should be the firing cone.  The flatter the bottom of the curve, the more "forgiving" the body will be to firing variations within the kiln as well as for general under or over firing.

 

You also then align this information with a MOR test curve for strength.  You are trying to get the minimum porosity and the maximum MOR to basically overlap on the same cone. 

 

3 percent porosity is a LOT.  Asking for issues in functional tablewares, in work destined for outdoor installations, or things like pool tile, and sinks and such.  Shoot for something below 1%.  The closer to 0 the better in general.  0.5% is a nice optimal target..........hard to hit without dropping the MOR.

 

best,

 

....................john  

 

Here Big Lou:

This graph shows how little range is where it is vitreous but still at max strength : and this is from a clay that is touted as having a much better range than most commercial clays:

(Matt and Dave clay: out of business though)

matt dave SCIENCE 25

 

 

 




#62419 Non-Legal Ways To Address Copying Issue

Posted by timbo_heff on 14 July 2014 - 11:36 AM

How about "sharing" your info but make it all incorrect thereby sending them on a big huge waste of time failure!




#58558 Are Dinnerware Safe Glazes Safe?

Posted by timbo_heff on 15 May 2014 - 10:54 AM

Send samples to Brandywine or Alfred for testing: that is the only way to know with confidence.

Doesn't cost very much... a bargain at twice the price




#57710 Reduction - What Is It Good For?

Posted by timbo_heff on 01 May 2014 - 02:33 PM

And there I was thinking I was having amazing deja vu experiences!!

In Scotland, "Hey you get offa macLeod!"   drew quite a different reaction to the track

Or were the stones amazingly futuristic??

"Hey you get offa my cloud"  Ah! things are so cyclic when you are as old as I am, makes me feel so "connected" :rolleyes:

This was on Garrison Keeler Prairie Home Companion so even though pretty off color, if it's clean enough for Garrison it must be clean enough for CAD:

 

Do you know the difference between Mick Jagger and a Scottish Highland sheep herder:

Mick says 'Hey hey you you get off of my cloud.'

and the sheep herder says 'hey hey McCloud get off of my ewe.'




#57643 Trimming Issues

Posted by timbo_heff on 30 April 2014 - 12:12 PM

Get a utensil crock from your kitchen: center it, attach to wheel with clay, coil some clay on the rim, cover with supermarket bag plastic to not muss up your new pot too much: Easy trimming chuck for most bottle shapes




#55901 Stacking Cone 6 Greenware In Bisque Firing

Posted by timbo_heff on 01 April 2014 - 01:33 PM

Be careful with the brown stoneware: those can bloat in the glaze fire if they don't get enough oxygen in the bisque fire> I would not tumble those but give them plenty of room




#55634 Porcelain Balls

Posted by timbo_heff on 28 March 2014 - 12:20 PM

How about a melon baller ?




#52704 Great Video On African Forming And Firing : Wow!

Posted by timbo_heff on 16 February 2014 - 10:27 AM

 I hand-built this yesterday after watching the African documentary above.

 

Did the technique of pushing and turning it into a round mold : 

Foot ring from the same mold.
Went a little kooky with the decorations, but a just for learning pot anyway.

(white stoneware with a little grog. banana for scale)

med_gallery_12660_647_511509.jpg




#52597 Great Video On African Forming And Firing : Wow!

Posted by timbo_heff on 15 February 2014 - 06:06 AM

Worth a watch !
 
http://youtu.be/52HKSwkI1hs


#51806 Looking For Recipe For Light Weight Kiln Bricks For Electric Kiln

Posted by timbo_heff on 06 February 2014 - 12:09 PM

Sounds like you've got the solution with the affordable bricks but there is also Litewate castable

Cast your own softbrick any shape you need : about a buck a pound dry:

http://www.sheffield...e-p/lvusl23.htm




#43970 Wedging Vs Coning Up And Coning Down

Posted by timbo_heff on 10 October 2013 - 09:47 AM

Related: Coning up and pushing down properly: aka power wedging is the secret to never getting an s-crack.

Zamek did a nice paper on the subject. Even with the most finiky clay the power wedge prevents these pesky little devils: important to really engage the clay down at the bottom area of the cone:

I have seen really experienced throwers start to get s-cracks and think it is a clay problem, but always once they read this, they realize that with age and arthitis etc, they really are not engaging the clay in the coning process, especially down low, like they used to. I have never seen this not solve the problem.
Some clays are more prone to s-cracks, but this is a good thing to assimilate into one's practice even if s-cracks are not a problem (at the moment)

here's the paper:

http://www.sheffield...ng S Cracks.pdf




#42839 Example Of Short Writing Assgiment In Japanese Ceramic Art History.

Posted by timbo_heff on 18 September 2013 - 02:47 PM

JB: I just got a nice book at a used book store last weekend: The World of Japanese Ceramics (sawyer)

Maybe I'll be able to take a stab at the assignment after I read it (and a few hundred other books )

 

All night stoking on a noribigama tonight though so I won't have my paper for you tomorrow, teacher san. (;




#42046 Clay For Large Figurative Sculpture

Posted by timbo_heff on 04 September 2013 - 10:25 AM

Sheffield has S-14: a really nice workable sculpture body (for up to cone 10): also 2 architectectural bodies if it is going to be super thick (reddish for cone 6 and a buff for cone 10) although temp usually not a huge factor in sculpture since they don't usually need to hold water




#31570 How to make bottoms less abrasive?

Posted by timbo_heff on 25 March 2013 - 08:31 AM

I have taken to burnishing the foot more when leather hard ... saves on dusty, loud post-firing finishing. Then a tiny hit with waterproof sandpaper finishes the foot very quickly with no dust.


#29366 Bone Head Mistakes

Posted by timbo_heff on 14 February 2013 - 11:09 AM

Have we all put a pot on the wheel to trim it, turned on the wheel without making sure pedal was off and had the pot (always a good one) fly across the room, or just me?