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Comment by Caryn Newman on November 21, 2012 at 6:48am

I have tested Floating blue on porcelain and stoneware.  Hideous murky green on stoneware.  Beautiful deep blue on porcelain.  Perfect on some pots, but with small sharp holes on others.  Does anyone have a clue about these?

Comment by Nadine Mercader on July 2, 2012 at 6:53am

Thanks Donna,  I understand about the floating blue and I am not making any so that will not be an issue.  I have never had the luxury of reduction but I do dream about it!  Someday when I win the lottery...I will keep you posted. N

Comment by Donna Kat on July 2, 2012 at 3:45am

The only glaze I have had problems with on a slow cool is floating blue.  It can turn a snotty green color (has rutile, cobalt and RIO as the colorants - I assume the rutile crystals are making the green).  Some people like it, I do not.  The high calcium glazes will be more matt like (satin rather than glossy clear) but that is what they are supposed to do.  Have you looked at the masteringglazes.com FAQ page?  I am guessing so since you mention them.  If I were doing reduction firings I would expect less but darn it, this should be less magic and more controllable in oxidation.  It seems we should be getting some benefit from the loss of the magic of reduction (which I miss a great deal).  Ok, that was my complaint for the day.  Do look forward to your next tests.

Comment by Nadine Mercader on July 1, 2012 at 3:56pm

You have me fir up (LOL) to try again! Do you know of any glazes that may be adversely impacted by the slow cool? I want to put my tests in a regular glaze fire and I don't want to be disappointed. I am making glaze this week and will set up my spray equipment.

Comment by Nadine Mercader on July 1, 2012 at 3:52pm

I will let you know what comes of it. Y

Comment by Donna Kat on July 1, 2012 at 3:28pm

I also like spodumene glazes (but miss the old grey spodumene).  The one I offered does not have the problem questioned in Annie's Tan (same basic glaze minus the rutile) and it may be because of the high amount of RIO.  It stands up well over time.  As I mentioned in the glaze recipe the synthetic RIO is another critical ingredient for me.  I agree that the test kiln was probably not adequate for an actual test since this glaze is so dependent on that soak and slow cool. Would love to hear if you get this worked out.  Always nice to have more information on what is working with a Saturated RIO glaze.

Comment by Nadine Mercader on July 1, 2012 at 6:32am

The link that you provided was to an analysis of Annie's Tan.  Johns comments concerned the very low alumina level.  From what I have learned if you don't have at least .25 alumina (unity value) then it will not withstand repeated dishwasher use.  I will try adding bone ash and switching the feldspar and then we shall see.  I really have great respect for John Post and John Hesselberth.  I fired to John Post's recommendation but I suspect that the test kiln was part of the problem,  it is a 110/20 amp and therefore I cannot connect it to my controller.  Also it is not vented so I vent via peep hole and that is not nearly as good.  I remember that after I added the kiln vent it made a huge difference in color development.  The additional reading that I have done is that these iron reds are finicky re a soak at cone 6,  some say not to others say one hour plus the slow cool! When it works I love the bricky red that the iron reds make.  On another topic I love what Spodumene does in glaze,  seems to make a much nicer glass.

Comment by Donna Kat on July 1, 2012 at 5:30am

My bad.  Your Randy's is completely different from any I have ever come across.  I tried several different Saturated RIO glaze recipes that work for other people and did not work for the studio I was in when we were having problems with the glaze.  Included in that was John Post's glaze which he put a lot of testing work in. The one posted worked for us.  You can switch the feldspar as well and see how that works for you if you decide to try it.  This glaze is mentioned on John Hesselberth's site.  The bone ash is going to make it slightly less opaque making it break a bit more but I was happy with it.  Testing in the big kiln may also make a difference because of the heat work.  I love this glaze when it works.  Hate it when it doesn't. JH's comment http://www.frogpondpottery.com/glazestability/glaze0015.html

Comment by Nadine Mercader on July 1, 2012 at 5:15am

Thanks Donna!  

Here is what gave my poor results:

Silica 30

EPK 5

Feldspar G200 20

Talc 15

Spodumene 12

Frit 3134 18

Additive:

Bentonite 2

RIO 15.

The unity values were good with silica at 3.995 and alumina at .290 

I don't know much about the Talc,  got it from Bennett's here in Florida.  I will find out what I can.  I will add the bone ash and when I have the courage to try it again will re-test in my big kiln.

Comment by Donna Kat on July 1, 2012 at 4:51am

Gerstley        33.5
Flint        30
F4 Feldspar    20
Talc        14
EPK        5
RIO Special    15.15
Bone Ash        2.5

Synthetic or Special RIO - Spanish RIO will not work

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