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Member Since 29 Oct 2012
Offline Last Active Jul 10 2017 04:46 PM

Posts I've Made

In Topic: Seeking More Technical Understanding Of Firing To A Cone

13 September 2016 - 11:01 PM

With apologies for inserting pragmatic queries into a mostly theoretical discussion, going back to your #8 comment, Neil, do you recall from your testing approximately what length of hold at cone 4 achieved cone 6 (and also the hold at cone 6 to achieve cone 8?).  


And what effect might firing to a lower temperature and holding to achieve the heat work associated with a higher cone have on an electric kiln?  My theory is that, if done consistently, it may prolong element life but wear out relays faster (assuming they are not solid state). 


I have recently moved to ceramics from working with fused glass where heat work is a well developed and quantifiable concept  as there is less variability in the chemistry of the materials.  Firing as "low and slow" as possible is often preferred to maximize control and consistency of the end result.  I'm curious about the transferability of this to ceramics.    

In Topic: Firing Plaster Of Paris

21 August 2016 - 08:49 PM

The basic recipe for molds for kiln-casting glass is 1 part silica to 1 part pottery plaster, by weight.  Sometimes other additives are included for various purposes.  Here's a link to get you started http://www.bullseyeg...tipsheet_08.pdf  See page 2 for the mold recipe.


This mold formulation crumbles away from a glass casting after firing in the range of 1500 - 1600 degrees F.  For your application, if the clay is already bisque fired there should not be an issue of it marring/adding texture to the surface.


Supporting a bisque structure for machining is an interesting concept and piques my curiosity.  Does the machining involve CNC?

In Topic: University Thesis On Obtaining Red/w No Lead

12 July 2016 - 10:31 AM

Strike firing glazes is an interesting concept.  Glazenerd, do your time/temperature descriptions refer to an eg. 30 minute hold at 1350F on the cool down from a glaze firing or an entirely separate firing starting with cold, glazed ware?  Would it matter which approach was used?

In Topic: Curious Question About Heat Rate Near Cone 6 - Slower Rate - Glaze Improvement?

17 May 2016 - 10:58 AM

There's an amazing amount of information in this thread.  Thanks so much.


Further to the rate of firing/slow cooling concept, I have been surprised at the amount of glaze alteration that can occur on refiring Cone 6 glaze fired ware to lower temperatures.  For example to mature china paint or attach decals.  I have seen noticeable permanent visual change in glazes when refired to as low as 1450F which must be below glaze softening temperature.  This has been most noticeable in titania containing glazes.  (Thank you Joseph for alerting me to that.)


To guide exploration of glaze manipulation at such very low temperatures I'm interested in further information and concepts regarding


Lowest temperatures at which permanent glaze appearance alterations can occur?


Glaze ingredients and combinations which may react at these lower temperatures? 

In Topic: Curious Question About Heat Rate Near Cone 6 - Slower Rate - Glaze Improvement?

14 May 2016 - 10:23 PM

The modifier glaze effects are dramatic.  Are you willing to share more about its composition?