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Member Since 31 Mar 2010
Offline Last Active Today, 10:55 AM

Topics I've Started

Iron Speckles

05 April 2015 - 10:45 AM

I have 2 glazes with the same colourants, 1 results in a amber colour with no iron speckles, the other is full of speckles. Same claybody, firing schedule used for both glazes. I know I could probably ball mill the speckled one but I'm wondering what is causing the iron to agglomerate in the glaze? ^6 electric, low coe glazes.


no iron speckles recipe:                                                

Silica 23.00                                                                   
EP Kaolin 14.00
Nepheline Syenite 10.00
Frit 3195 16.60
3134 4.80
Australian Spodumene 15.00
Dolomite 15.00

Bentonite 2.00
Manganese Dioxide 3.00
Iron Oxide Red 2.00



Silica 34.50
Wollastonite 5.00
EP Kaolin 23.00
Minspar  12.00
Gerstley Borate 22.00
Talc 3.00
Dolomite 3.00
Nepheline Syenite 2.90

Manganese Dioxide 3.00

Iron Oxide Red 2.00



I don't think the higher silica levels in the second recipe is the culprit, I'm thinking the lithia in the first recipe might have something to do with it? Boron differences?

Any thoughts most welcome.

China Marker

31 March 2015 - 03:43 PM

Thought I would share what I have found to work for marking test tiles easily and cheaply. The Dixon (Hi-Heat) China Marker pencil in brown lasts through ^7 oxidation firings on my test tiles. It stays clear and legible and is way cheaper than the ceramic underglaze pencils. ($7- for a dozen china pencils on Amazon versus around $12 for one ug pencil)  It's kind of waxy so doesn't smear or rub off if you wipe glaze drips off bottom of test tiles. It doesn't leave any ghost marks on the kiln shelves.


It does burn out with glaze overtop but for test tiles it's brilliant. Haven't fired it hotter than ^7 so don't know if it will do ^10 but I think it would.



Critique - Worst You've Heard

27 November 2014 - 01:27 PM

Seems to be a fair interest in critiques lately.Wondering what comments people have heard.


One of them that I had back in school was "Got anything else?"  Prof didn't even deem my work good enough to make any constructive criticism on. I still remember it, but with a smile these days.



Clay Ph

26 November 2014 - 03:57 AM

I use a slip that is mostly OM4 which I need to reduce the shrinkage of. Slip needs to be alkaline when applying to green ware, will calcining part of it alter the ph? My other thought was to add a tiny bit of soda ash, in place of part of the 3134, to increase alkalinity if necessary. (slip is for mocha diffusion and on my clay it either cracks or gets gritty from lifting slightly) Anybody done this or have any thoughts?

Huge Pots

15 November 2014 - 12:26 PM

Came across a blog that describes how in France huge terra cotta pots are made using a heavy rope wrapped sectional armature. The armature is made to be removed prior to firing. This method hasn't changed in hundreds of years.


The blog which describes the process pretty well is here: http://www.deborahsi...de-garden-pots/


Anybody doing anything like this here?