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Member Since 06 Apr 2010
Offline Last Active Today, 10:11 PM

Posts I've Made

In Topic: Inside Mug Color Change

Today, 03:45 PM



Insight Level II from Digitalfire.com.  I have been using that since god was a kid.  The program has all the capabilities you will EVER need.  And with a science type background, your husband will likely enjoy the subscription access database / website that comes with the Level II version.





In Topic: Inside Mug Color Change

Today, 11:36 AM

OK... venturing into "dangerous grounds" here................  going off the "politically correct" spectrum........


This discussion above cuts to the core of one of the things I always mention in my ceramic chemistry classes.  Which I think is VERY important for students to really understand.  It gets to core ideas of "how the world works".


In general, how someone gets to be a "famous ceramic artist"........ is from the visually apparent aesthetic qualities of their work, the technical execution of the pieces (from a forming standpoint), and is often combined with the way they present themselves in public settings (exuding a professional feeling and being nice people).  Maybe add in a dose of "right place at the right time" serendipity, and also a bit of a "who you know" factor.


What this "fame" does NOT necessarily tell you is their depth of understanding of the technical sides of the process.  For all anyone knows... they flunked or got a D in their ceramic materials / ceramic chemistry / kiln design-building classes (if they ever had that kind of training).


They may have mastered the aspects of the process to get the visual result THEY use...... but that might be the real limit of their technical expertise.  They might even have had training that was not all that accurate, and are sharing that stuff once again, spreading the misinformation.


So just because "Famous Ceramist" shares some glaze recipe or some ideas on the technical side of things........ that does not make it automatically "truth".  There are things I've seen printed in studio ceramics oriented books that fly in the face of basic science and engineering principles.


Sometimes the information presented by "Famous Ceramist" is taken out of context, and then transferred to others incorrectly.  For example, a glaze used solely for sculptural work gets shared... and then a participant in a workshop comes back and shares it with their functional potter table-ware producing friends.  Suddenly it shows up on tableware.  Then that tableware potter (maybe who has little technical knowledge) becomes "famous"... and that glaze then goes on to be shared as a tableware glaze.  And so on.


Vet your sources folks, vet your sources.  Sometime the emperor has no technical clothes.






PS:  Luckily, most of what we do is not "death incarnate".  But having a good grasp of some basics is important.

In Topic: Inside Mug Color Change

Yesterday, 08:30 AM

Just ran it in Insight.  Also it is WAY oversupplied with KNaO for both cone 6 and cone 9.  (Other oxides are within limits).  Those are not helping with the leaching stability either.





In Topic: Inside Mug Color Change

Yesterday, 08:22 AM

OK without doing ANY formal glaze calculation in Insight...... let's look at  that colorant supply. 


That's a total of 10.3 percent of metallic oxides.  There are few to no glazes that can hold that kind of saturation of such coloring oxides in solution as the glaze melt cools.  Just ain't gonna' happen.  So some of the coloring oxides are going to precipitate out on the surface of the glaze.  Any oxides that are in this condition are almost certainly subject to easy leaching into strong-ish acids and bases.


Then looking at WHICH oxides these are.  Copper is notoriously hard to keep in solution in glazes.  And at 4% that oxide alone is flirting with the top amount that can even closely be stable.  Then there is 4% of cobalt OXIDE.  That alone is enough to make the glaze almost black and be supersaturated.  The manganese is there just for good measure to totally make this absurdly oversupplied with colorants. 


Then take into account that this looks like a Cone 6 recipe.  At Cone 6 a significant amount of boric oxide glass is introduced to lower the melting point.  Boric oxide glass is softer than silica glass... so this is a less durable base than if it were at Cone 9-10 or higher.  SO the glass has a lower ability to hold the oxides that are still IN solution also.  (note... yes adding B2O3 in very precise proportions to the SiO2 can harden borosilicate glasses... but just looking at the recipe, I don't thik that is the case here.)  If this is getting fired atr cone 9-10....... worse... don't need that boron.


NOT a glaze for food bearing wares.  Period.





In Topic: Inside Mug Color Change

19 December 2014 - 07:31 AM

Please give us the recipe with percentages / amounts.