Comment

Comment by Norm Stuart on May 9, 2013 at 5:11pm

We have Gwalia Spodumene Concentrate from Australia. It's 75 micron, which is another way of saying it's 200 mesh.

http://www.armadilloclay.com/images/Spodumene.pdf

But when I mixed Vee's Tenmoku Gold, in the horse photo below, I replaced the Spodumene gram for gram with Lithium Fluoride.

Lithium Fluoride is more expensive than Lithium Carbonate or Spodumene, but it's very fluxy and impossible to break apart into Lithium and Fluorine at kiln temperatures. Lithium and Fluorine allegedly give off more energy than any other reaction when they combine - so pulling the two apart requires the same amount of energy.

http://www.axner.com/lithium-fluoride.aspx

Comment by Sylvain Boucher on May 9, 2013 at 9:19am

Hi Shine, I use spodumene 200M. that's all i know, i bought it in canada, at SIAL.

Thanks

Comment by Shine Chisholm on May 9, 2013 at 7:21am

Which Spodumene do you use?

Comment by Jeff Poulter on March 13, 2013 at 12:35pm

I have been using the Special Red RIO from Ceramic Supply for the last little while & it certainly gives better results than regular RIO. I have also just ordered some Precipitate from Standard, so I will do some testing to see which gives a better red.  It would be nice to get really nice reds w/o having to re-fire in a bisque.  Jeff

Comment by Norm Stuart on March 12, 2013 at 3:19pm

George - Finding your detailed essay on "Iron Glazes and Achieving Red Color in Oxidation" in Google was what first made me aware of cone6pots.ning.com. It was exactly the information I was looking for at the time.

As I experimented with temperature holds during cooling and using ferric phosphate . . . I also became aware of the printer's pigment "Iron Oxide, Red Precipitate" which is purely the rhomboidal Hematite formation and certainly looks much different to what I had been buying as red iron oxide.

Since it's the same price as what is normally sold as "red iron oxide" I've found that, when firing no higher than cone 6, it's often simpler to start with bright red iron oxide. The only difference is that this type of red iron oxide is refractory rather than a flux like black iron oxide.

In buying the Phosphoric Acid to make ferric phosphate you mention in your essay, I also discovered mixing Phosphoric Acid with Wollastonite to repair or replace damaged kiln brick.

Discovering how cone 6 differs from plentiful historic information about cone 10 firing is the most interesting part of ceramics for me at the moment. Thank you so much for what you and others have put into this website.

Comment by George Lewter on March 12, 2013 at 1:23pm

What started here as a picture evolved into quite a discussion.  For cross referencing purposes, and to eliminate a lot of repetition, I want to link it here to the pre-existing discussion on iron reds.

http://cone6pots.ning.com/forum/topics/iron-glazes-and-achieving-re...

Comment by Norm Stuart on March 7, 2013 at 10:55pm

This is a piece glazed with alpha-phase "Iron Oxide, Red Precipitate" in Vee's Temmoku Gold

I'm unhappy with the variation of "Cornwall Stone" so I've substituted the Cornwall Stone using Tony Hanson's suggested formulation on Digitalfire.

http://digitalfire.com/4sight/education/substituting_cornwall_stone...

100.6%    Vee's Tenmoku Gold ^6
23.4%    Silica
18.6%    Custer Feldspar
14.5%    Nepheline Syenite
10.0%    Iron Oxide, Red Precipitate
 8.0%    Whiting
 7.8%    Kaolin
 7.2%    Dolomite
 5.5%    Spodumine
 2.3%    Ferro Frit 3134
 2.0%    Wollastonite
 0.9%    Borax
 0.3%    Soda Ash
 0.2%    Zinc Oxide
 0.2%    Strontium Carbonate

You can see the red iron oxide turned to black on the mane. The mustard yellow/ gold crystals form during the slow cool, 50F/hour between 1800F and 1500F.

It's not my sculpture, but I'm proud of my glaze.

Comment by Norm Stuart on March 7, 2013 at 10:37pm

Red Iron Oxide Fe2O3 occurs more than two phases. The two primary structures are:

Alpha phase is a rhombohedral structure and bright red, called Hematite;

Gamma phase is a cubic structure and brown colored, called Maghemite.

http://en.wikipedia.org/wiki/Iron%28III%29_oxide

NASA explains these two Fe2O3 iron oxide colors dominate the surface of Mars.

http://minerals.gps.caltech.edu/mineralogy/Recent_Projects/mars/ind...

When firing to Cone 6, the phase structure of your Iron Oxide makes a big difference in the finished glaze, even if the oxide isn't contaminated with extraneous material like Barium Sulfate

Comment by Norm Stuart on March 7, 2013 at 10:11pm

I discovered not all "Red Iron Oxide" is the same.

We're within local truck delivery from Laguna Clay, so getting metal oxides with our clay is free delivery. But I never obtained a bright red glaze, regardless of suggested holds at various temperature while cooling, when using Laguna Clay Red Iron Oxide. It is a dark-red powder which creates a brown looking liquid glaze.

Looking at the Laguna MSDS for their "red iron oxide" I found it even lists inclusions of 5% to 15% barium sulfate. http://www.lagunaclay.com/msds/pdf/3rawmat/adry/mirox4284.pdf

When I ordered something called "Iron Oxide, Red Precipitate" from Standard Ceramic in Pittsburg PA, the powder is a very bright red, the liquid glaze is bright red, and the finished glaze is bright red - except for thin sections on the ceramic where there is enough heat to start breaking the red iron oxide down into black iron oxide. I've discovered "Iron Oxide, Red Precipitate" is used as a dye in printing ink. http://www.standardceramic.com/Materials.html

I've asked Jon Brooks if Laguna could carry this and so far the answer is no.

I've also found Cone 6 to be quite different to Cone 10 in the way that the type of colorant oxide I start with has a much greater effect on the finished result simply because less heat work leaves a lot of ingredients less changed. I don't know why this surprised me.

Using Insight and Digitafire I made a glaze which used Talc, and reformulated it so the Talc was replaced with Silica and Magnesium Carbonate. The glazes are identical in chemical analysis, but you would never guess they're the same glaze after firing both to Witness Cone 6, even when a one hour hold is added before slow-cooling. There's just not enough heat and time to make these glaze look the same. Different raw materials make a difference in the final product.

Here's a photo I just took of the "Iron Oxide, Red Precipitate" on a porcelain dinner plate. It sure looks a lot different from the brown stuff Laguna sells as "red iron oxide".

Comment by Darlene Shemanski on October 25, 2012 at 8:16pm

you're right!!! Thx

• ‹ Previous
• 1
• 2
• Next ›
• Page