I like this glaze alot!  Is it fairly stable? And how is red iron precipitate different from red Iron oxide?

I've found "red iron oxide" comes in a variety of purity. The one from Standard Ceramics beats Laguna hands down as it is pure red iron oxide and doesn't contain barium sulphate. Laguna Red Iron Oxide tends to fire brown to dark brown in our kiln at Cone 6.

Firing to Cone 6, the Red Iron Oxide Precipitate remains stable - except on thin areas of the ware which receive more heat where it breaks down to Black Iron Oxide. I'll be comparing the Standard Ceramics "precipitate" with "Special Red Iron Oxide" from U.S. Pigment.

These tiles were fired to Cone 6, held for 30 minutes and slow-cooled at 50F between 1,800F and 1,500F. A differing firing cycle could change the resulting look of the glaze.

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

Other posts on this subject:

http://cone6pots.ning.com/photo/img-0380?commentId=2103784%3ACommen...

I got my RIO Precipitate from standard today so I can mix up another small batch.  I'm wondering if I should try & find my crocus martis or stick with the purple ochre.  I was in a hurry last night & wanted to get the test piece in with the other pot so I didn't look as long as I could have.  I guess I could have gone to the local supply and gotten yellow RIO.  I also have a bag from Ruelev(spelling?) that is an artist supply house.  It is a Red Hematite.  I have done a couple tests in other glazes with it & it makes things come out more reddish-purple.  So many tests, so few test tiles!  

I used Yellow Iron Oxide, which supposedly just 88% of Red Iron Oxide. The LOI being water, hydroxyls.

I went into this believing the H20 firing off the Fe2O3.H2O is not relevant, and probably isn't. 

But I've already been surprised already that one ingredient or another can make a glaze difference in the relevant Cone 6 range when you're not first firing to Cone 10.  I have an open mind at the moment.

If you look at the bottom of the tile on the left, you'll see two tiles are made of white clay, specifically Laguna Stoney White. http://www.lagunaclay.com/clays/western/wc412.php The tile on the left fired vertically and the one on the right horizontally with very little difference in appearance.

Bear in mind the kiln fired periodically to achieve a 50 degree per hour cool between 1,800 and 1,500 which makes glazes more crystallized and matte. But glossy glazes still come out glossy.

Can you post a photo of your tile?

This is a two layer Oil Spot on a vertical tile which slid during the melt exposing areas of the tile.

We originally held for 20 minutes to let glazes lay flat, but I was intrigued with idea that we weren't giving Brownian Motion sufficient time to complete reactions in a viscous melt, so we started holding 60 minutes. Another idea was that a one hour hold, by definition creates the heat work of the next higher cone (or so I've read at Orton) so we could better densify some of our clays without actually reaching a higher peak temperature which would decrease the viscosity of our glaze melts, many of which run badly at cone 7.

I've recently been comparing 30 minute holds at the top to 60 minutes, as I did for this Orange Street glaze.

I've previously tried George Lewter's hour holds at about 962C, which improved glaze using the Laguna Red Iron Oxide, which is partly not red iron oxide. But it did not compare to using pure Red Iron Oxide.

I found a note that John Britt cites 1,239C (cone 7ish) as the point where Red Iron Oxide converts to Black Iron Oxide, the link below says it begins at 1,220C, so a cooling hold from Cone 10 would be important. But it seems simpler to maintain the Red Iron Oxide used as the glaze ingredient by not reaching 1,239C.

http://books.google.com/books?id=TApnGTVLwxAC&pg=PA189&lpg=...

But this is also a function of time, where reactions require a certain amount of kilocalories / mole of Red Iron Oxide, the number Google doesn't seem to yield at the moment. For this reason I cut back the 60 minute hold at 1,222 to 30 minute in case it begins to diminish red iron oxide.

Deciding what to start with rather than a mixed powder like Laguna red/black also makes sense since Red Iron Oxide is refractory but Black Iron Oxide is a flux above Cone 010.

I look forward to your photo.

Here is the pic.  Had to take it inside as it is snowing again today.  Will spray a pot tomorrow if the weather cooperates.  Also will do some testing subbing out the Yellow Iron Oxide and also some layering.

I've noticed there's obviously an equilibrium reaction between the iron level in a clay and the iron in a glaze during the melt.

Iron in a glaze always seems to first find its way to the surface of a white clay, with only the amount of iron unreacted with the clay remaining in the melt. Likewise many glazes on a high iron clay develop spots resulting from iron migrated out of the clay and inti the final glaze.

Your glaze tile resembles "aventurine" iron saturation glazes I've tried using 15.2% iron oxide, where the glass in the glaze crawls away from the refractory iron oxide.  It seems likely I'm losing part of the iron oxide into my white clay to get the result I have. I'll try to find some piece of bisqued high iron clay to try Orange Street on in our kiln.

It is thicker on the left side & you can see the surface is more of a solid color.  I will put this in my next bisque to see what that does to it.

Orange Street fires with a shiny surface on brown clay in our kiln as well.

This is the same glaze as above on iron rich brown clay, fired the same way to Cone 6 with an hour hold at the top and a slow-cool of 50F between 1,800F and 1,500F - just as with the white tile above which fired matte.

On brown clay I'd reduce the Red Iron Oxide as there's an equilibrium reaction going on with the iron in the clay, even though only black iron oxide is supposedly a flux. So instead of 12% iron oxide red precipitate I'd try 9% or so.

I notice you slow cool at 50•c/hr to 962•c.

In centigrade our 50F/hour slow-cool is,  10•c/hr from 982•c to 815•c, which is much slower, but I think the big difference is the clay as seen below on our brown clay.

Others have come to similar conclusions ten years ago  (and likely fifty years ago and five hundred years ago). Because of "trade secrets" I'm certain there's been a lot of reinventing the wheel going on in ceramics since it began.  Just like Europeans creating majolica when attempting to reverse-engineer China's porcelain technology.

It was interesting reading declassified Army research papers, published just after WW-II, which recounted attempts to reverse-engineer the chemistry of gold and other metal lusters because the process was secret to German firms like Meissen and there proved to be military uses for applying thin films of metals on ceramics.

http://www.potters.org/subject61502.htm/

Paul Lewing on tue 11 feb 03
on 2/10/03 7:52 PM, Carol Tripp at cjtripp@HOTMAIL.COM wrote:

> I'm working on Michael Bailey's brilliant iron orange, and it only tuns
> out
> dull brown. Has anyone tried it and have any suggestions?

All of these iron reds are very, very dependent on two variables (at least).

One is the particular kind of iron you use. When I first started testing them, I tested black iron, yellow iron and seven different kinds of red iron.

You want to use the iron that is the brightest color before it's fired to get the brightest color after firing. And the firing cycle makes a huge difference. Slow cooling is probably a must.

Paul Lewing, Seattle

I also pulled this "Persimmon" glaze out of the kiln made with Iron Oxide Red Precipitate.

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

I'll try refiring this at Cone 06 to bring out more red, as George Lewter relates Lana Wilson suggested.

It's certainly a far cry from the photo below of Persimmon Red fired at Cone 10, probably in reduction, shown on Promethian Pottery.

http://prometheanpottery.wordpress.com/2009/12/

Touchstone Red has so much red iron oxide it reminds me of Aventurine Iron Saturation glazes I've tried.

Frit 3195 40.00
F-4 Feldspar 13.00
Talc 18.00
EPK 6.00
Wollastonite 5.00
Silica 18.00

One of these Aventurines splatters while firing which is not nice. I was trying to find a way to duplicate Amaco Jewel Brown which forms Iron Silicate crystals or something on a black or dark brown background.

Linda Arbuckle often states in her hand-out that she hasn't tried this glaze, and no photos, so I consider a lot of her recipes as "a rumour of a glaze" rather than an actual glaze recipe.

65.9%    Aventurine  ^04  John W Conrad
39.7%    Silica
38.8%    Borax
15.2%    Red Iron Oxide
7.0%    China Clay
2.7%    Boric Acid
2.2%    Barium Carboate


105.6%    Aventurine  ^04  John W Conrad
39.7%    Silica
38.8%    Borax
15.2%    Red Iron Oxide
7.0%    China Clay
2.7%    Boric Acid
2.2%    Barium Carboate

http://lindaarbuckle.com/handouts/glz_hg_lowfire.txt       

124.00%    Aventurine (Brown Iron with Coppery Crystals)
75.0%    Gerstley Borate
25.0%    Silica, Imsil A-25 - Si 46.75%
24.0%    Iron Oxide - Red 4284 Ferric Oxide
       
http://lindaarbuckle.com/handouts/glz_hg_lowfire.txt       

121.0%    Aventurine ^04  crackle
70.0%    Frit 3269
15.0%    Boric acid
7.0%    Whiting
3.0%    Lithium carbonate
5.0%    Silica
20.0%    Red iron oxide
1.0%    Bentonite
6.0%    Barium Carbonate - makes glaze reddish
small metallic glitter crystals. Boric acid is soluble - mix glaze fresh
apply thick or glaze will be dull brown.

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.

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.

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

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.

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.

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. 

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.

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

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.

Using just 5301 Frit 100%, with 20% added Silica, and 24% Red Iron Oxide is the best for Cone 6. The best was Spanish Iron Oxide shown below. vThese tiles came out of our kiln using our 50F/hour slow-cool between 1,800F and 1,500F

Making a Cone 6 Aventurine glaze with 24% Silica added was a bust - no crystallization at all with a slow-cool - too much silica.

Where the glaze is applied thicker, as on this white clay tile below, there are larger macro-crystals with a glaze color like your vase, and best of all it doesn't run at all. I guess red iron oxide really is refractory, as is silica.

This is the same recipe with the silica level raised from 20% to 24%. Fired in the same kiln on the same shelf, but not the same look at all. No reflective crystals - just a glassy brown.

These are some interesting macro-crystalline Aventurine glazes.

http://s3.excoboard.com/exco/archive.php?ac=t&forumid=64484&...

I just mixed-up some John Britt Goldstone, from his book "The Complete Guide to High-Fire Glazes: Glazing and Firing at Cone 10".  I'll fire it as is, and add additional flux if needed.

http://books.google.com/books?id=5klq2XOXYaUC&pg=PA139&lpg=...

Two new variations of Orange Street at ^6 with the 50F cool/hr between 1,800 and 1,500.

Orange Street with 10% Mason Stain 6450 Praseodymium Yellow  (Pr Si Zr), seen mostly in the crevasses.  I read a comment from someone that red iron glazes often look more red when laid on a yellow underglaze.

Orange Street with an even sprinkling of granular Ilemenite.  Brown crystals crowd-out the orange crystallization.

Jeff, I think if you explore Ron Roy and John Hesselberth's Waterfall brown glaze, you will see it has the same variegation that Mossy Mahogany has. You can play around with that, maybe omitting some of the iron, adding some copper, etc. Waterfall Brown is a cone 6 glaze, so you should be able to play around with it and come up with something close to Mossy Mahogany.

June

Hi June,

   That is a really good idea!  A couple people on this forum have used it over porcelain & it kind of looks similar.  On porcelain, I think it overfluxes just a little and most of the green travels to the bottom of the piece & has a little variegation in it. I did a test tile with Waterfall Brown and Frogskin that looked promising.  Couldn't tell a lot because it was horizontal instead of vertical.  I should try that on the next cull I have.  Also someone posted about using Emeraude with WB to get the same effect on regular clay instead of porcelain.  I have some Emeraude so I should try that as well.  Also Norm here did one of his base glazes with nickle in it that did a nice variegation.  It was more of a light turquoise color.  Really cool.  Some many tests, so little time....  jhp

Jeff, another thing to try is  Waterfall green over some rust colored glazes (something with rutile and iron). Another one I'd try if Floating green and Floating blue over a black, and over a rust. Both of those glazes have breaking qualities from rutile.

I read some of the messages on their web page and they said that most of their glazes had something like 7 to 14% of iron in them.  So that maybe a clue for you. Also, check up on some hare's fur formulas as base.

I'm up to my ears right now with Cone 04 slips and other tests, otherwise I'd give the above a go.

June

I can offer you this fairly standard Hare's Fur recipe.

But it only looks like this without a slow-cool.

Almost all slow-cooled Hare's Furs I've tried turn out black, most glossy, some matte.

The exception is Chappell Floating Blue which ends up like this when slow-cooled . . .

Jeff, I think your best bet is a rutile blue or rutile green, etc. under a tea dust or other temmoku. Here's a URL that shows the effect: http://justanothermudbug.blogspot.com/2008/12/two-mediocre-firings....

In oxidation, if you omit the cobalt which is usually present in those reactive rutile blue glaze recipes for oxidation, and maybe add a about 4-5% iron, you might get something as a starting point, either alone or under a tea dust or other temmoku. If under, you might want to skip the extra iron and just use the rutile and no cobalt.

June

I notice the blog writer fired these glazes to cone 12.  I wonder if the effect is the same at cone 6?

(My clay doesn't bloat like the students' clay so the glazes came out extra-glossy and they actually look pretty nice for ^12.)

Norm, you can get the same effect using cone 6 glazes. Floating blue is a rutile, reactive glaze for cone 5-6. Try that variation as I mentioned earlier, with a teadust and other cone 6 high iron glazes over. Try the reverse too - with the temmoku etc. under the floating blue variations.

Also, I looked up that Bath potters blue glaze, and it looks like there's some granular illmenite in there to give it the spots. There's a commercial glaze called Stardust, available in the U.S. that looks similar to the blue you mentioned. You might want to try that one.

June

Hi June,

    So you were looking at the KGE18?  It is mostly light blue with the dark blue patches?  Do you think I should try adding illmenite to a couple of blue recipes? I have been able to replace the other 2 glazes that I use in that combo with glazes that I can make, so this would be the last one I need to replace.  Who makes the Stardust that you are talking about?  I have used the one from Stone Mountain Clay & also Spectrum.  Is it from somebody else?  I would like to try Norms Hares Fur over & under my layering combos.  Hopefully, i will get my e18t back up & running soon.  I guess i could make some shorter things to go in my Skutt in the meantime.  jhp

Norm and Jeff, I did a bit of detective work and found out that the Mossy glaze is a single glaze, according to the creator.  I'm pretty sure it's a cone ten version of a reactive, rutile glaze with iron and either chrome or copper added to it.

I don't know what claybodies you use; but I don't remember if Emily, who created the Mossy glaze uses a white or buff body. If she does and you use a darker body you might want to test these over white slip as well as your regular, iron bearing body.

Here are three non blue versions of a cone 6 Floating blue - 2 green and one red. I think these would be the answer. I would combine both the floating green and floating red in equal parts  and then do a few more mixture with say 2/3 iron and 1/3 green, etc and just keep refining it to get it the way you want. One of their pots looked like there might be a bit of blue in there as well. Have a good time playing with this. Let me know how it goes. Wish I had time right now to do this.

Floating Green (the person posting this on Clayart said she used this firing schedule)

Fired to cone 6 (1220c) in oxidation.

Firing ramp:
100c (212f) per hour to 600c (1112f)
150c (302f) per hour to 1100c (2012f)
100c per hour to 1220c (2228f)
15 - 30 minute soak depending on matts and glosses used.
cool down 100c per hour to 900c.
Natural cool down to 150c (approximately 15 hours)

Recipe:

30 Nephelite Syenite
21 Gerstely Borate
8 Whiting
10 Kaolin
31 Silica

ADD
2.0 Chrome oxide
1. Cobalt oxide
============================================================
Floating Red - Cone 5-6 - Not known to be food safe - For Decorating Only (PS: I don't know why they says not food safe unless it's too much iron.)

(all numbers expressed as % by weight)

Gerstley B 55
Talc 15
Silica 30
Total 100
Add:
RIO 22

To stop running, lower Gerstley Borate to 45 and add 10 epk. It will still hold the ed color.

Or Substitute Feldspar for up to 50 % of the Gerstley Borate to reduce running.
============================================================
Frogskin ^6 ox Don Goodrich

22 Custer feldspar
22 Gerstley Borate
22 Nepheline syenite
26 Flint
3 Wollastonite
3 EPK
2 Titanium dioxide
3 RIO
4 Copper carbonate
 

June

PS: Yes the Stardust I found is one of the ones your mentioned. Just look up Moonlite, which is a cone 9-10 rutile glaze and see how much illmenite is in there, and use that amount with granular illmenite for your test. Sometimes they use manganese dioxide for spots, but that stuff isn't good to use if your in your studio during firing. The fumes and the dust are toxic.

June Perry - Having more glaze experience now, I'd guess the colorant in Promethian Mossy Mahogany is Nickel Carbonate with Rutile.

Nickel carbonate creates both the Amber Brown as well as the green moss look in this ^06 low fire as well.

I call this ^06 Olive Speckle.

100%  Ferro Frit 5301

  10%  Nickel Carbonate

    1%  Bentonite

Promethian ^10 Mossy Mahogany

Aargh - lost my message before it posted. Start over! I just did some more research on this yesterday and it seems that this is a cone 10 oxidation recipe using that top glaze over an iron bearing mahogany brown glaze. I don't think it's nickel in that recipe since nickel does not always break up or grow crystals like that in all recipes. It's more likely it's a version of a rutile type glaze. Floating blue is  cone 6 glaze like this and there are a couple of green versions out there. John Hesselbert has one one his website in the glaze formulas section, and there another different one out there. You can see some blue in the Mossy version, so I suspect there are equal parts copper and cobalt in there. I would do a version that way and then do one with a bit more copper than cobalt. I'd probably do each other those with a few percent of red iron oxide as well. If you go to google and search out Floating blue, you will see similar variegation and just imagine it with copper as well as cobalt in the recipe and it revealing the iron brown glaze and the top glaze moves. These chun type glazes do move which is why they're their most beautiful right before they run off the pot!

My stubborn detective work paid off. Here's their etsy page. This link should take you directly to the page of sold pots with pictures of this glaze. As I thought, it's a cone 10 version of Floating green, over a Sienna brown glaze. This should give you a great starting point.

http://www.etsy.com/shop/PrometheanPottery/sold?ref=shopinfo_sales_...

Till later,

June

Most excellent!  Thank you June.

Norm. I know I might have asked this before, but is this with your classic 50F/hour 1800-1500 schedule cooling result? It is pretty lovely and shows some really nice texture. I have used orange street before but didn't get a result like this. I had way more crystals and not as much matting.