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Comment by Norm Stuart on April 8, 2013 at 7:31pm

A visible example of how iron migrates from the glaze melt into clay, more so in white clay.

Persimmon Glaze with 9.8% Red Iron Oxide Precipitate

http://cone6pots.ning.com/forum/topics/recipes-for-testing

Tile on the left fired to ^04 with iron already migrated out of the glaze melt leaving yellow glass,

Tile on the right fired to ^6 with 50F slow cool between 1,800 and 1,500.

One, two, and three coats from one coat on the upper right on the left, and from one coat on the bottom on the right tile.

Comment by Norm Stuart on March 30, 2013 at 10:35am

It's interesting that Ferro Frit 5301, 9% Fluoride, confirms my suspicions that Fluoride does not off-gas but binds with other meals such as Aluminum, Calcium and Silica - off-gassing two Oxygen atoms.

http://en.wikipedia.org/wiki/Fluoride_glass

After buying Lithium Fluoride from Laguna Clay, I confirmed that a pile of Lithium Fluoride by itself on a non-reactive surface will weigh the same after firing as it did before. The various glaze programs like Insight need to be rewritten to incorporate this reality.

I found these older posts from 1999 by Michael Banks in New Zealand on this topic.

http://www.potters.org/subject19000.htm

Comment by Norm Stuart on March 29, 2013 at 6:05pm

This is 100% Ferro Frit 3269 with 20% Red Iron Oxide (various types) - fired fast to ^05 with no slow-cool

Once we get Ferro Frit 5301 I'll re-post.

I try to use Xanthan Gum to suspend and harden pure frit glaze recipes as all the gum off-gasses. I've found adding 3% white-firing Bentonite can often add hazing to a glaze or alter it completely.  As an example adding 3% Bentonite to Frits CM-940 and CM-941 cause them to bubble and blacken. In this case I'm comparing the tiles in the third and fourth column - without and with 3% Bentonite.

Comment by Norm Stuart on March 27, 2013 at 9:20pm

Thanks so much.

Before they run out to buy the 5301 frit, I'll try this with the similar 3269 frit. The difference that sticks out is 3269 has 1% zinc oxide.

It's always interesting to see which of these ^06 to ^04 glazes tolerate being fired along with a load of greenware to be bisqued.  Frit CM-941, a leaded cadmium sulphide red, turns black from the slight reduction atmosphere and the prolonged heating. 

Comment by Jeff Poulter on March 27, 2013 at 6:26pm

As quoted from Janet DeBoos:
FF 5301-100
Bentonite-3
RIO-20
^05-04
Overfiring will lessen the sparkle as will prolonged soaking at top temperature. This glaze can become a lustrous metallic copper color in both oxidation and reduction by the addition of 1 part copper carb.
I have added the copper carb before but haven't gotten any luster but it does change the color of the sparkles.

Comment by Norm Stuart on March 27, 2013 at 12:29pm

I like the look of Mossy Mahogany but I don't like Emily's comments about it, "It’s a real pain to apply – too thin and it’s just brown, too thick and it runs all the way down the pot during firing in olive drab puddles"

http://prometheanpottery.wordpress.com/tag/emilys-mossy-mahogany-gl...

It took adding 20% 3269 frit to Pete Pinnell's Weathered Bronze Green until it became a reliable glaze.  This sample is from the faster slow-cool with all three batches combined - so the Lithium flux is provided by 1/3 Lithium Carbonate, 1/3 Lithium Fluoride, and 1/3 Spodumene. When I mix it again I'll use just Lithium Fluoride.

A similar glaze I like over texture is Lana Bronze Aqua http://www.flickr.com/photos/glazes/1084691061/

This is how it always turns out for us using Laguna's current version Gerstley Borate, slow cool or fast. You'll notice the only problem is it creates "texture" where there is none. I'm not completely sold on the 3% bentonite in this recipe.

Comment by Jeff Poulter on March 27, 2013 at 11:45am

Speaking of Promethean Pottery, I would kill to get their recipe for Mossy Mahogany.  Of course it would have to be brought down to ^6.

Comment by Jeff Poulter on March 27, 2013 at 11:41am

Hi Norm

  I will post it as soon as I get home.  I have a kiln cooling right now where I am trying to salvage the vase that had the Crocus Red and Aventurine.  It worked great on the test but didn't like the L&L firing.  I re-sprayed and it came out worse.  Last nite I sprayed it with some Coyote Sunrise Shino, so I'll see how that comes out.  This Saturday I am doing the Orange Street and the 2 versions of Touchstone.  Jeff

Comment by Norm Stuart on March 27, 2013 at 11:26am

Jeff  --  There are people at our studio who would be eternally grateful if you could provide the recipe for that ^04 Aventurine - the glaze on your vase is exactly what they want.  I know some people who will be driving down to Laguna clay for an emergency purchase of a bag of Ferro Frit 5301.

Last night I experimented with a ^6 firing with a much faster slow-cool of 85C/hour between 1,038 and 815C, rather than our usual 10C/hour, between 982 and 815C.  Vee's Tenmoku Gold turned glossy without the yellow colored flecks. I'll try your 50C/hour and 38C/hour to achieve a less expensive slow cool before returning to our lavish 10C/hour.

But Orange Street came out just slightly glossier on this white clay tile with this much faster slow-cool. The extra iron in brown clay has a much bigger effect in creating gloss.

Comment by Jeff Poulter on March 27, 2013 at 10:47am

I have a ^04 aventurine that I have used quite a bit.  I can dig it out for you if you want.  It is basically 5301, some bentonite & RIO.  I don't think I have made it since getting the "Special" RIO, so I should probably give that a try.  Here is a pic of what it looks like with regular RIO.

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