Jump to content


Member Since 06 Apr 2010
Offline Last Active Today, 10:30 AM

#124765 Need Pictures Of Kiln With Pottery Fired Too Hot In It

Posted by JBaymore on 03 April 2017 - 09:58 PM

Can't find a bigger picture file of this one.  Sorry.  This image was part of some written documentation work I did when I did some consulting for a ceramics cooperative type place that I did kiln work for.


It shows the bagwall and floor of a cone 10 firing in a gas kiln when some low fire white clay got mistaken for porcelain clay.







#124717 How Did They Do That?

Posted by JBaymore on 02 April 2017 - 09:18 PM

Was the inside a shino?  If so, very common technique.


A lot of post-firing work is done on many woodfire pots.  Usually with diamond surfaces tools.  Working from coarse to fine grits.  If you do it well......... it is quite functional.  It takes time to do this stuff though.


Most woodfirers routinely sand the surfaces of a lot of the pieces with 200, 400, and 600 grit wet/dry silicon carbine paper as a general step in the finishing process.





#124542 Is Anyone Going To Nceca?

Posted by JBaymore on 30 March 2017 - 03:30 PM

The 2017 Portland OR NCECA Keynote Address:  https://www.youtube....h?v=ORRLBpqM3BY





#124540 Red Clay And Manganese Dioxide...

Posted by JBaymore on 30 March 2017 - 03:12 PM

Welcome to the forums.


No way to make it "food safe".  It is WAY far from a 'glaze".  Call it a "surface" or a "patina".  And to keep it from running it should go on THIN.


Also research information on manganese fume issues from kilns.  Serious stuff.





#124531 Metal Frame For Sprung Arch Kiln

Posted by JBaymore on 30 March 2017 - 11:32 AM

Mark brings up an EXCELLENT point that I make all the time in my kiln building workshops and classes......... that a lot of potters tend to kind of "miss".  Steel flexes.  You have to understand this concept to make a good kiln buttress frame (or a frame that deals with the racking forces of a hinged door).


I've seen many a "saddleback" sagged sprung arch because someone did not get this idea when they designed the actual buttress member that sits behind the arch skews.  Near the corner uprights the steel does not move .....but in the center of the long span.... it bows outward.  This lets the center of the arch sag.  Over time... it bows permanently.  Kiln slowly starts to look like an old tired work horse.


Another important point is that steel flexes MORE when it is getting hot.  So you have to make sure not to enclose the steel within refractories.  Allow heat energy to dissipate off the surface to the surrounding air.  Otherwise it might be inflexible enough when it is cold.... but when hot... it bends.  


Since  about 1980 I have used channel steel for resisting flexing for arch buttress spans (also for kiln car frames) .  Flat face against the back of the skew bricks.  And flat face up toward the car kiln's floor refractories.  If you use angle for the arch buttress ... do NOT put the one side of the L inside a groove in the refractories.  Unless the kiln is a "short term one".  (This also accelerates rusting in the hotter steel area.)





#124456 Help With Substitute For Lead Bisilicate

Posted by JBaymore on 29 March 2017 - 09:55 AM

Welcome to the forum.


Make sure to read up in detail on the appropriate handling of lead materials before you get too far into this.  To handle them safely in the studio is not impossible but difficult. 


Lead is one of the great fluxes...... except for this one little itty bitty issue,..........


There is nothing that is a direct sub for lead bisilicate.  Bismuth and boron are the usual suspects to start investigating.





#124404 Glaze Additive/s

Posted by JBaymore on 28 March 2017 - 04:08 PM

Bentonite at 1% in all glazes even those with some decent clay content.  Dry mixed with the batch.  No issues with clumping.


Sometimes epsom salts sometimes defloculant (Darvan #7), as needed. Sometimes glycerine or propylene glycol.  Sometimes gum or CMC.    (Sometimes even Elmer's white glue.)


Sometimes red food coloring (to identify the glaze layer.... not for fired color).


Depends on the specific glaze and what makes it "work" for me.





#124401 Claystories 3 At Nceca

Posted by JBaymore on 28 March 2017 - 03:13 PM

Do you know if NCECA ever has any plans to put some of the talks up on youtube?


Some is already up.  They don't put everything up... but some of it.









#124348 Claystories 3 At Nceca

Posted by JBaymore on 27 March 2017 - 10:36 AM

As is usual... one of the best presentations at NCECA each year.


Robin Hoppers video presentation was tough to watch.  Such a great guy.





#124347 Is Anyone Going To Nceca?

Posted by JBaymore on 27 March 2017 - 10:34 AM

Just got home myself!   Wonderful trip and I loved Portland!!  Introduced myself to John B.  Chatted briefly with Marcia but never made it over to where she was stationed....  I think I might have seen Sheryl Leigh a time or two but she didn't have her respirator on!!




Very nice to meet you and put a face to the username.  Thanks for doing that.





#124335 What Might This Be?

Posted by JBaymore on 26 March 2017 - 08:48 PM

Ran it in Insight... could be a crappy cone 3 glaze....or a really crappy cone 6 glaze.  (low in boron....very low in silica.)


 EP Kaolin...................  750.000 
 Dolomite....................  750.000 
 Gerstley Bor (99).......  300.000 

          CaO      0.545*  
          MgO      0.435*  
          K2O      0.003*   
          Na2O     0.016*   
          P2O5     0.001*   
          TiO2     0.004    
          Al2O3    0.314   
          B2O3     0.120    
          SiO2     0.721   
          Fe2O3    0.004    

              Calculated LOI:  29.758
                       Si:Al:   2.295
                      SiB:Al:   2.679
           Thermal Expansion:   6.980
              Formula Weight: 134.230

#124334 Qotw: Do You Have A Question For Us?

Posted by JBaymore on 26 March 2017 - 08:34 PM



Wanted to say THANKS for all the work you've done on the QOW. 





#124027 Claystories 3 At Nceca

Posted by JBaymore on 19 March 2017 - 11:15 AM

CLAYSTORIES is one of the "must sees" at NCECA.





#124003 Case Of An Enlarged Bubble?

Posted by JBaymore on 18 March 2017 - 05:36 PM

 An enlarged bubble can sometimes be caused by irrational exuberance. 





Oops......... I thought this posting thread title was about the stock market.  ;)

#123998 Potters Council Members / Show / Reception / Portland Nceca

Posted by JBaymore on 18 March 2017 - 03:04 PM

As always....... NCECA is an exciting "gathering of the clan" kind of event........with total clay overload. I'm looking forward to maybe seeing some fellow Potters Council members at the Portland NCECA. I'll be at NCECA all week, some times at the NHIA (non-profit area) table, and for sure at the PC Reception.   In case you forgot, remember that you got this notice in you inbox a little while ago:



Join us! We have two great events you won't want to miss at NCECA March 22-25 in Portland, Oregon.
  1. 2017 Potters Council Juried Show — We have such talented members and we're excited for you to see their works in person! The display will be open March 22-24 in the exhibit hall. Click here to get a sneak peek of all of the pieces selected. Then stop by booth #602 in the Resouce Hall to see them in person!
  2. Member Reception  Come see us on Wednesday, March 22 from 5-6pm in the Skyview Terrace inside the Oregon Convention Center. There will be food, a cash bar, prizes, and friends. Feel free to bring a clay buddy as well!
We have a special offer for those of you coming to NCECA: Renew onsite and receive an extra 10% off any book or dvd purchases in addition to our show specials!