[Clayart] recent work - reacting glazes at an interface

carol at knighten.org carol at knighten.org
Fri Sep 9 21:19:26 UTC 2022

Hi Vince -

Re that red - I've seen it before where there is no phosphorus.

You see it below, though its transparent:


Yet small flecks of that color are common in glazes containing phosphorus, or
in the interaction region where one of the glazes contains
phosphorus. Examples below:

Below there are bits of that red to be seen in the closeups of a high
phosphorus inlay, which is a mottled orangy-red.


Below, in an inlay containing phosphorus, dots of that red, and an
equally intense yellow are seen:


I have however never seen any red that intense covering a large area.  We know
that the color of copper red is directly related to particle size.  The
cadmium sulfide pigments used in painting can be any color from pale yellow to
deap red, depending on particle size.

My guess is that the particle size determines the color of that crystal, and
that the range of particles sizes is narrow.  I've seen that splatter of red
interspersed with particles of equal sized copper colored metallic crystals.

Below in the glaze iron_satIron_Z2W_Z2Z_0, one can see the occurance of both
the tinsy bright red crystals, and the similar sized coppery metallic


To sum up, I've no idea what those crystals are, yet I think its particle size
that determines its color, and that they are related to the tinsy coppery
colored metallic crystals that are so common in my high alkali metal glazes.

I consider it likely that the red particles seen in the above glazes are not
all the same kind of crystal.


vpitelka at dtccom.net writes:
 > Hi Carol - 
 > That mug is amazing - so much to look at!  And the closeups should be
 > printed as wall posters or framed art.  They are lovely, dramatic
 > abstractions.  
 > What's producing the bright crimson crystals?  Do you think that the very
 > small amount of phosphorus present is interacting with the iron to create
 > those crystals?  That fits into the recent discussion about whether adding
 > bone ash or TSP to a saturated iron glaze helps it to go red, but I've never
 > seen one go THAT red.  
 > - Vince
 > Vince Pitelka
 > Potter, Writer, Teacher
 > Chapel Hill, NC
 > vpitelka at dtccom.net
 > www.vincepitelka.com 
 > https://chathamartistsguild.org/ 
 > -----Original Message-----
 > From: carol at knighten.org <carol at knighten.org> 
 > Sent: Thursday, September 8, 2022 11:05 PM
 > To: clayart at lists.clayartworld.com
 > Subject: recent work - reacting glazes at an interface
 > Hi -
 > glazes reacting at a vertical interface:
 > http://carol.knighten.org/2022-GlazeTests/2022-09-09-reactingGlazes-4/
 > Carol
 > -- 
 > ============================
 >     Carol Marians       
 >     (541) 296-4528
 >   carol at knighten.org 
 > http://carol.knighten.org
 > ============================

    Carol Marians       
    (541) 296-4528
  carol at knighten.org 

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