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Comment by Nadine Mercader on May 10, 2013 at 2:22pm

Norm, 

The Orange Street you showed is EXACTLY what I am trying to create.  Is this formula on the sankey database?  Thank you so much for the very informative post!  Nadine

Comment by Jeff Poulter on May 10, 2013 at 2:09pm

Hi Norm,

    I will have to check when I get home, but I believe NMC is where I bought my Crocus Martis from.  I have too many bags & haven't gotten them all into containers yet.  I buy a few containers every time I find myself at a dollar store.  Some are good enough to put liquid glazes in & some are relegated to dry contents only.  It's much easier to scoop out of a container than it is a plastic or paper bag.  I'm rambling..... Jeff

Comment by Norm Stuart on May 10, 2013 at 12:58pm

Next time I buy red iron oxide it will be the 97% pure Bayferrox 180 New Mexico Clay sells as "crocus martis". The balance of the material is silica, moisture and LOI.

U.S. Pigment did not send me an MSDS. Their red iron oxide "precipitate" is obviously a Laux process precipitation product, whose purity depends on what impurities are found in the scrap iron they use at the Chinese factory. Based in results it's far more pure than Laguna "red iron oxide" but without an MSDS it's a pig in a poke.

Comment by Norm Stuart on May 10, 2013 at 12:17pm

Since the 1970s synthetic nearly pure red iron oxide has become very inexpensive to produce using a series of different patented methods by Bayer.

The Bayer method http://www.google.com/patents/US4299635 starts with man-made iron sulphate because crystallization can be a very inexpensive method to achieve greater than 99% purity.

This is a photo of Iron Sulphate, also called Copperas.

The original Bayer method calcines off the sulphate to create nearly pure red iron oxide. The resulting material is mixed and ground with 0.5% to 1% silica then washed and dried. The added silica provides the finished product with favorable flow characteristics. Products like Bayferrox 130 and 140 have a much higher level of silica, around 6%.

Food grade C.I. Pigment Yellow 42 is 99% pure Yellow Iron Oxide, add 2% Silica to help it flow easily and it becomes C.I. Yellow 569, also food grade.

In addition to low-silica red iron oxides like Bayferrox 110 and 180, Bayer also sells technical iron oxides without silica for use as chemical catalysts - this is their Bayoxide line of products. If you're looking for a bright red iron oxide, bayoxide is not what you're looking for.

Digitalfire suggests that "crocus martis" contains 20.88% SO3. But there's no sulphate left in the Bayer process. But sulphate is added, in the form of Barium Sulphate, in the following cheaper Laux precipitation process.

The much less expensive Penniman and Laux precipitation methods start with scrap iron combined with either iron sulphate or waste iron chloride from metal pickling baths. Iron is precipitated in an acid bath using nitrobenzene or similar nitrogen compound. http://www.google.com/patents/US6086846

The red iron oxide produced by this method is the red iron oxide sold by Laguna Clay. Because of the various other metal impurities in the scrap metal and the pickling solution, Barium Sulphate is added to the finished product to convert soluble metal compounds into insoluble metal compounds. The resulting MSDS shows why this product makes a brown glaze rather than a red glaze at cone 6.

http://www.lagunaclay.com/msds/pdf/3rawmat/adry/mirox4284.pdf

The "red iron oxide" precipitate product of the Laux method could be made more pure by using iron sulphate and controlling the type of scrap iron used, but this increases the cost to the point where the customer is better served paying the premium to purchase the Bayer method product.

The cost of producing a chemical rises exponentially when you start adding extra 9s to the purity.  A 99% pure chemical may be pretty cheap to make, but making that 99.9% pure will be a lot more costly. Making it 99.999% pure runs up the cost very quickly.

A salesman may call their product 100% pure, but the MSDS they're required to provide with the chemical will quickly clarify that "100% pure" is not actually on offer. My grocery story sells "pure water" from Fiji in plastic bottles, but this not really pure water - something you might have already guessed if you have ever visited Fiji. Making "pure water" for pharmaceuticals, which is actually pure, starts with a minimum $3 million price tag for procedures the pharma industry calls GMP (Good Manufacturing Practices).

None of our ceramic products are GMP pure. Most are dug out of the ground, ground and bagged with a level of purity which can be analyzed and is disclosed on the MSDS.

Comment by Jeff Poulter on May 10, 2013 at 11:19am

Hi Norm,

    I'm sure glad that you're out there doin' the diggin'!  I hadn't even thought to look at what the MSDS sheets said.  I had thought about the RIO from US Pigment.  I will probably get some the next time I need to get some molybdeum. For iron reds I've always tried to use the most red RIO that I could find.  On other glazes, like you say, it almost better to have some impurities and variation.  I haven't even mixed up anything with the precipitate yet, but last night I did make up a test batch of the ^04 Aventurine using the Special RIO.  It went over another glaze so I won't really be able to judge the change.  I fit looks good, I will post a pic.  If its a turd, then it will get something else sprayed on it & put back in the kiln!  jhp

Comment by Norm Stuart on May 10, 2013 at 11:02am

I too have replaced red iron oxide with spanish iron oxide (Prominfer) in many glazes, like this Ron Roy's Nutmeg.

Being a natural product like rutile, Prominfer creates variation in the glaze as it melts. Synthetic irons are extremely uniform so are more suitable for iron reds like the second tile with Orange Street.

Ron Roy's Nutmeg with spanish iron oxide (Prominfer) instead of red iron oxide

http://www.flickr.com/photos/glazes/1084685267/

Orange Street with Bayferrox-180 97% red iron oxide

Comment by Shine Chisholm on May 10, 2013 at 6:25am

If Sigma-Aldrich's price is a good guideline, you could expect a 97.3% pure red iron oxide compound to be $2,860.62 per pound.

An important distinction that you have not brought up at all is that whatever it is that people call crocus martis is either a calcined impure iron oxide or an iron sulfate. *big* difference.

Finally, my supplier (Rovin Ceramics in Ann Arbor, Michigan), recommends using Spanish iron oxide whenever a recipe calls for red iron oxide.

Comment by Norm Stuart on May 9, 2013 at 9:15pm

I'd say the label is an exaggeration. The reagent chemical company Sigma-Aldrich sells 99.999% pure red iron oxide, the most pure commercially available but it costs $162 for twenty five grams - that's $2,940 per pound.  http://www.sigmaaldrich.com/catalog/product/aldrich/529311

No one sells 100% red iron oxide, certainly not for $5.48 per pound. You can buy Bayferrox 180 which is 97.3% pure red iron oxide from New Mexico Clay for $7.12 a pound or for $8.91 a pound from Highwater Clays. Both vendors list it as "crocus martis".  Is the extra 3.3% purity worth the extra $1.65 a pound?  If it is, then that's what you buy.  http://www.nmclay.com/Amazing/items.asp?Cc=GLAZEMAT

Trust the MSDS linked on your vendor's website. They're required by law to list the ingredients, and they list Bayferrox 130 and 140 as the products you're buying. Both products are 94% pure red iron oxide, which has a "Chemical Abstract Service" number of CAS#1309-37-1. http://ceramicsupplyinc.com/iron-oxide-special-red.aspx

All Bayferrox red iron oxide pigments are calcined in a way which makes them very resistant to breaking down into black iron oxide or other colors. They're all good products.

Comment by Jeff Poulter on May 9, 2013 at 7:13pm

I just looked on the container and it says 100% RIO.

Comment by Norm Stuart on May 9, 2013 at 5:50pm

It looks like your red iron oxide from Ceramic Suppy Inc.  is 94% pure, fairly low compared to more than 99% for other Bayferrox products, but higher than naturally mined red iron oxide. What's more interesting is you're essentially buying the same product again as "crocus martis" but with a larger particle size.

Bayferrox 180M is far better at 97.3% Red Iron Oxide, with 1% LOI, and just 2% unspecified. This product is what Highwater and New Mexico Clay sell as "crocus martis".

http://bayferrox.com/fileadmin/pdf/IPG/00006289_000_BF-180-ENG.pdf

As is Bayferrox 110 at 97.1% Red Iron Oxide, with 1.2% LOI, and only 1.7% unspecified.

http://bayferrox.com/fileadmin/pdf/IPG/00006114_000_BF-110-ENG.pdf

On the Ceramic Supply website, click on the "MSDS Sheets for Raw Matierals" link.

http://ceramicsupplyinc.com/help-and-links.aspx

this curiously enough takes you to "Standard Ceramic Supply's MSDS website".

http://www.standardceramic.com/MSDSmaterials.html

Then click on the ingredient you want, in this case Red Iron Oxide Precipitate - they don't list "special".

http://www.standardceramic.com/MSDSmaterials/Iron%20Oxide%20-%20Red...

It shows Iron Oxide Precipitate is Bayferrox 140

Bayferrox 140 is:

http://bayferrox.com/fileadmin/pdf/IPG/00006254_000_BF-140-M-ENG.pdf

94.2% RIO, 1% LOI, 4.8% unspecified.

Click on "Crocus Martis" and you find you're buying Bayferrox 130 which is essentially identical to their Bayferrox 140 red iron oxide precipiate. The particle size on Bayferrox 130 is 0.3 microns, double the 0.17 micron size of Bayferrox 140, but is otherwise exactly the same product.

http://bayferrox.com/fileadmin/pdf/IPG/00006211_000_BF-130-M-ENG.pdf

It pays to ask your vendor what product you're actually buying.

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