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Comment by Jeff Poulter on May 9, 2013 at 1:56pm

Hi Norm,

   So how pure is the "Special Red Iron Oxide" from Ceramic Supply?  It is the one that I have been using lately for my RIO.  Also I have been using the purple stuff for Crocus Martis, but like I said before, I also have used another purple hematite that I got from an art supply place that mainly caters to oil painters, so this was a pigment that is used in oil painting.  Just wondering.  jeff

Comment by Norm Stuart on May 9, 2013 at 11:09am

Here's the iron oxide sourcing information from U.S. Pigment.  http://www.uspigment.com/chemicals.shtml

Our High Purity Iron Oxide is from China and is about 99.5% average.

Spanish Iron oxide is the same what every one is selling, its about 82% iron oxide and it is imported by Hammill and Gillespie and is distributed all over the country.  (I assume this is Promindsa's Prominfer product)

Pink Iron Oxide is also from China and is about 80% iron oxide.

Natural iron oxide is mined in Michigan and is only 70% iron oxide.

Yellow Fe3O4 is a food grade C.I. Pigment Yellow 42 made by Bayer.

(Most iron oxides from China are copies of one of the Lanxess Bayferrox pigment products, licensing their production techniques from Bayer - at least as soon as Bayer finds them and sues them)

Comment by Shine Chisholm on May 9, 2013 at 5:36am

Norm, I could do some research. Whatever this is certainly acts differently than any other iron oxides I've used.

Comment by Norm Stuart on May 8, 2013 at 11:29pm

Where do you buy your Crocus Martis, or do you know what it consists of?

Each ceramic supplier provides commercial iron pigments for each type of iron oxide or crocus martis they supply, but it seems few suppliers choose the same commercial iron pigment for each type of iron oxide.

When asked for "Crocus Martis", which has not been available for many years, some suppliers say it's not available, some sell "Spanish Iron Oxide" as crocus martis, which is usually a product called "Promifer", mined by Promindsa in Spain, but some suppliers provide one of the six Promindsa "Micronox R" products instead as "Spanish Iron Oxide".  http://www.promindsa.com/product/

Other suppliers sell a mind-boggling array of synthetic commercial iron pigments as Crocus Martis.

Here's Digitalfire's general take on it. http://digitalfire.com/4sight/material/crocus_martis_249.html

The Crocus Martis supplied by Standard Ceramic is Bayferrox 130, which is 96% Fe2O3 and 3% Silica and Alumina. While their red iron oxide precipitate is Bayferrox 140 which is only 94.2% Fe2O3.

Highwater supplies Bayferrox 180M when asked for Crocus Martis, and a partially natural product called RedCAST® from Prince Minerals as Red Iron Oxide.  http://www.highwaterclays.com/index.cfm?fuseaction=feature.display&... 

http://www.highwaterclays.com/index.cfm?fuseaction=feature.display&...

The Crocus Martis New Mexico Clay sells is also Bayferrox180 which they describe as "Purple Iron". http://www.nmclay.com/Amazing/itemdesc.asp?ic=CROCUSMARTIS

They sell Yellow 569 as yellow iron oxide, which is 98% FeO-OH and 2% silica.

http://bayferrox.com/en/products-applications-bfx/product-search/ba...

The look of your glaze is similar to Orange Street glaze I make with Bayferrox 503, or preferably Bayferrox 222, in place of red iron oxide. http://bayferrox.com/fileadmin/pdf/IPG/56190590_000_BF-503-ENG.pdf

http://bayferrox.com/fileadmin/pdf/IPG/00006319_000_BF-222-FM-ENG.pdf

When a recipe like Orange Street calls for both red iron oxide and crocus martis, I use yellow iron oxide from Laguna Clay/Axner in place of the crocus martis, which seems to create the right glaze color.

Although Laguna Clay describes their "Yellow Iron Oxide" as "A weaker form of iron—high clay content",

the MSDS for their Yellow Iron Oxide actually lists >99% pure CAS-51274-00-1 aka (FeO-OH) - hey, where's this alleged "high clay content"?  http://www.axner.com/ironoxide-yellow.aspx

It leaves us ceramacists without much actual guidance when a recipe calls for red iron oxide, yellow iron oxide, or crocus martis. They're names without much specific meaning.

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