Mcs Glazes, Which Rio?

[clay lover]

I have been using many of the glazes from this book, Mastering Cone 6 Glazes, by Roy and Hesselberth, for a few years, always mixed with Spanish RIO. Have any of you used other RIO's when called for in these glazes? What can you tell me about what changes to expect if using Special RIO instead?

I use Waterfall and Varigated Blue a lot as well as Raw Seinna.

I know, test, test, test, but do you think I will see a difference?

[OffCenter]

I think the amount of iron in the various iron oxides varies from batch to batch. A year or so ago I started using Spanish RIO for all glazes calling for RIO because in my testing of iron saturate glazes the Spanish RIO looked better than RIO, Yellow Iron Oxide, Crocus M., Yellow Ochre, and High Purity RIO. Recently, I gave out of Spanish RIO and used RIO and the glaze looked better than with Spanish RIO so I may switch back. High Purity RIO looks as good as Spanish RIO and RIO but mine speckles and I don't want to bother ball milling it.

 

Maybe John255 and Min will jump in here. They have a lot of experience with iron saturate glazes. I think Min recently posting something about switching back and forth between Yellow Iron Oxide and Red Iron Oxide.

 

Jim

[oldlady]

could the rest of us learn what Mcs means, please?

[JLowes]

Mcs refers to the book "Mastering Cone Six Glazes".

[Bob Coyle]

I had been wondering what "Spanish" iron oxide was as opposed to just plain RIO

Here is a quot from a clayart thread that may explain the difference...if any.

 

 

Tom Buck on tue 29 apr 03

       I will chime in. The following is what I learned many years ago
    when I did some articles on bacterial mining (the Canadian application was
    recovery of uranium from abandoned hard-rock mines). Such mining began in
    Spain long ago, and as far as I know the mine still is in operation.

    There are at least 20 separate names for iron oxide red either
    occurring in nature or slightly upgraded from a mineral deposit. This
    mineral is impure Iron(III) Oxide which chemists now use as the preferred
    name for "Ferric Oxide" nowadays).

    In Spain, there exists one large orebody assaying low amounts of
    iron sulfide (mostly), too inadequate for steel-making even with modern
    "float sink" technology. Long ago, however, an astute person noticed that
    rainwater would pool, then evaporate and leave behind a mineral that
    turned red on roasting. In time, it was discovered that a specific
    life-form (a bacterium, named bacillus ferro ferroxidans) used the iron
    sulfide as food (an energy source). The bacterium did its thing in water
    in contact with the iron mineral. the result is to solubilize the iron as
    Iron(II) Sulfate or FeSO4. This solution is run into evaporation ponds,
    the green crystals recovered and then roasted to form Spanish red (iron
    oxide red).
    To keep costs as low as possible, the mine operators in Spain are
    happy with a Iron Oxide Red purity that ranges from 83 to 88 percent by
    weight. If you as a potter were able to obtain Spanish Red as such bag
    after bag, then you'd tweak your recipes to get the best glaze colour.

    Sadly, our dealers seem to buy from different sources, and neglect
    to tell us the purity level of the new Iron Oxide Red now on sale. Much of
    our RIO now comes from automobile scrap that hasn't been digested by
    Ferroxidans. And since we are not told what contaminants are included in
    this RIO, our glazes misbehave, especially the high RIO crystallines.
    Is there a solution to this problem? For most of us, not likely
    since we do not want the get into chemical processing. We should ask for
    an analysis of the RIO offered to us, and hope it is suitable for our
    needs.
    til later. Peace. Tom.

    Tom Buck ) -- primary address.
    "alias" or secondary address.
    tel: 905-389-2339 (westend Lake Ontario, province of Ontario, Canada).
    mailing address: 373 East 43rd Street, Hamilton ON L8T 3E1 Canada

[OffCenter]

The iron content and lack of impurities is what is important. Natural Red Iron Oxide is 85% iron. Spanish RIO is 83-88% iron. High Purity or Synthetic Red Iron Oxide is 96-99% iron. Crocus Martis is a brand name for High Purity RIO so it would be 96-99% iron. I didn't know that until I found the above info on http://ceramicartsdaily.org/wp-content/uploads/2011/03/cmtechnofileiron.pdf. As mentioned above, my High Purity RIO has specks but Crocus M doesn't, so I'm thinking Crocus M is the way to go for any glaze needing RIO. Since it is so pure the recipe may need adjusting. Since it is a synthetic it shouldn't vary from batch to batch like the natural RIOs.

 

Sorry, Claylover, I know you were asking about specific glazes in Mastering Cone 6 Glazes and no one has addressed that yet.

 

Jim

[clay lover]

That's OK, Jim, any info is helpful. I have some crocus martis so I will mix a test of the ones I use the most and see what happens.
As to the abreviated title, I'm sorry , I thought I had seen that book referred to here as MCSG. It is considered by some to be one of the best books on ^6 glazes out there, and many ^6 potters use the formulas in it.  I have edited the OP to include the title and authors.
Since they are so widely used I figure someone on here will have tried various RIO and could give me a head's up.

[oldlady]

i recognized the glaze names and i am familiar with the book.  i just never heard it referred to that way.  mr hesselberth told me how to fix the glaze that i mismeasured because i left the 1000 gram weight on the bar when i made the nutmeg recipe.  who would have guessed that the addition of some ball clay would fix it.

 

have to ask jim some day about a recipe i have that includes crocus martis.  i do not have any and wonder what i can substitute.

[OffCenter]

i recognized the glaze names and i am familiar with the book.  i just never heard it referred to that way.  mr hellelberth told me how to fix the glaze that i mismeasured because i left the 1000 gram weight on the bar when i made the nutmeg recipe.  who would have guessed that the addition of some ball clay would fix it.

 

have to ask jim some day about a recipe i have that includes crocus martis.  i do not have any and wonder what i can substitute.

 

Since Crocus Martis is the same as High Purity RIO that means it is about 97% iron. Therefore, you could sub plain RIO for the Crocus M. but since RIO is about 85% iron you have to increase the amount by 12%. So, if you're mixing up 10,000 grams of glaze and the glaze calls for 6% Crocus M. you would need 600 grams of Crocus M. but you will get the same amount of iron by using 672 grams of RIO.

 

Jim

[clay lover]

So does that mean that if I want to try CM instead of RIO, I REDUCE the amount of C M by 6%?  Use 6% less Crocus Martis than the RIO  amount called for in the glaze?

[John255]

So does that mean that if I want to try CM instead of RIO, I REDUCE the amount of C M by 6%?  Use 6% less Crocus Martis than the RIO  amount called for in the glaze?

Clay Lover,

You are getting some very good info here on iron.

However, a line-blend will tell you how the iron in your bag is working with all the other variables in your operation.

If you want to see some photos have a look at this thread.

http://ceramicartsdaily.org/community/topic/4340-comparison-of-slow-fast-cooled-iron-reds/?do=findComment&comment=37830

I hope you get it all ironed out very soon.

Regards,

John255

[OffCenter]

So does that mean that if I want to try CM instead of RIO, I REDUCE the amount of C M by 6%?  Use 6% less Crocus Martis than the RIO  amount called for in the glaze?

 

I'd say ~12% would be better because RIO has 12% less Iron. In the example I gave in previous post the amount of CM in the glaze was 6% which was 600 grams in a 10000 gram batch. If that recipe had called for 600 grams of RIO instead then you would reduce that about by 12% for 528 grams of CM. (I hope my math is right. I'm not double-checking.) Obviously, the % could be off by 2 or 3 points and there could be a whole host of other variables like even how the 15% impurities in RIO affect the glaze. The only way to find out is to test.

 

Jim

[OffCenter]

Oh good! While I was writing my last post, John joined the discussion. Now, if Min will jump in.

 

Jim