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GreyBird

Hudson River Clay

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Curt, I gave a description of the tile in my last post: Silica increases from left to right, and Whiting increases from top to bottom. So it isn't a Currie grid, but the bottom left corner still has the most flux. This is a useful test when your starting glaze doesn't have much clay, but has relatively high alumina.

Mary, I fired the tile flat. This is not an example that shows increased fluidity, but I can dig up some if you're interested. I should add that the results of firing flat vs vertically can be fairly different. There's some discussion in the Currie thread about how to get the most info from flat tiles, including some indication of fluidity.

By the way, the reason Insight gives different UMF numbers than what you calculated is that it doesn't include iron as a flux.

Glazenerd, I haven't heard of iron being involved in shivering. I thought lithium was the main suspect.

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Just now, Pieter Mostert said:

 

Glazenerd, I haven't heard of iron being involved in shivering. I thought lithium was the main suspect.

Pieter:

The Hudson slip is the glaze. In Mary's early tests, 78% of the recipe was Hudson: to which 8.4% was iron, more specifically magnetite. So effectively, the brittleness/stress normally associated in a clay body from that % of iron,  is being transferred to a thin coat. One of the gaping holes in clay chemistry is the effects of reduced iron on COE. While a calculator may transfer the iron molarity into the total flux column, it does not accurately project changes in COE. 

While the carbon content is fairly low in this clay as indicated by the 2.35% LOI,  the effects on magnetite specifically is unknown. In addition, the nearly 25% natural flux content results in a COE significantly higher than normally found in a formulated recipe. The COE is in the same range as Frost porcelain: approaching 7%. So that compounds the effects of high iron content. I ran her recipe at 60% Hudson addition, while maintaining the 10% lithium addition: which produced no shivering. One of those rarities that does not fit traditional chemistry.

Tom

 

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2 hours ago, glazenerd said:

One of those rarities that does not fit traditional chemistry.

But does produce lots of fun experiments! :) I want to go through the Currie Tile Method information Curt mentioned before I proceed. I really like the layout of the cubes as pictured by Pieter and does seam to be good method to teat different additions at different amounts. But first I have to go out and get chicken feed... doesn't life just keep getting in the way!

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On 10/2/2018 at 11:42 PM, curt said:

As someone else said, see the Currie Tile Forums thread elsewhere here in the Glaze and Chemistry section for a practical way to explore the full range of possibilities with your found material.  If you go down that road I have no doubt that you will find many different glaze chemistries of interest.

Hi Curt,

I have not gone out to get chicken feed yet... got stuck reading through the Curry Tile Post. I looked into getting the book but its' $75 on Amazon! ... Maybe I'll just give it a whirl on my own for now. With the Hudson River Clay I can not strip out the Silica and Alumina, but I can still see using this method with pure HRC in top left corner and Gertslet Borate top right, Frit 3134 and Whiting in the remaining two maybe? 

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Mary my thought is that you would substitute in the Hudson Clay for the clay normally used in a glaze recipe (maybe that is what you mean).  However, in his book currie does make some specific suggestions for testing wild clay.  Will see if I can find that.

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Hi Curt, I am actually looking to make a glaze out of the clay altering it as little as possible. Much like a lot of the old Albany Slip Recipes you see. In those recipes however, My Tiles Shivered when mixed with Albany Slip and also when Mixed with Hudson River Clay.

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2 hours ago, Pieter Mostert said:

Mary, Ian Currie published his book on the grid method under a Creative Commons licence, so you can obtain a free electronic copy here.

Oh, Thank you so much! That is terrific. Going to check it out now. I ended up going back to the river today for another clay haul... it was a big one. I slept for an hour when I got home!

IMG_2945.jpg

Edited by GreyBird

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OK, so after looking over the Ian Curry stuff, Don't think it's really applicable to what I'm doing here, but... I still like the layout of the squares and that for quick batches of lots of tests you can stack them saving space in the kiln so I'll definitely make use of them. I'm actually kind of using his method as I plan on doing a line blend with my Hudson Clay and one other material... four different versions. Then when I see how they come out I'll make adjustments. Who knows in the end maybe I'll end up using all 4 corners after all :) I like the time and space you can save and then when you see stuff that works you can then test on a vertical standing test tile.

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Mary:

after reading several abstracts on natural hematite clay deposits: that is a hematite deposit :) hematite rich natural clay shows  dark gray color, and cleaves brown where oxidized iron shows. I know you were hoping you found an Albany deposit, sorry. Personally, I find this clay much more fascinating. 

Tom

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2 minutes ago, glazenerd said:

Mary:

after reading several abstracts on natural hematite clay deposits: that is a hematite deposit :) hematite rich natural clay shows  dark gray color, and cleaves brown where oxidized iron shows. I know you were hoping you found an Albany deposit, sorry. Personally, I find this clay much more fascinating. 

Tom

No worries at all. It is interesting enough that I will thoroughly enjoy discovering it's possibilities and limits. I was not really hoping it was Albany, I just thought it might be because the Early Glacial Lake that created the Albany Slip came down this far. But the fact  that it is not makes it even more interesting... Maybe I CAN make a cool glaze that no one has seen before :)

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 Maybe I CAN make a cool glaze that no one has seen before 

actually Mary, I suspect that is a very strong possibility. Given the iron%,  the crystal habit of hematite, in addition to the refractive index: very strong possibility.

t

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All I want to do is go down to the basement and work on my tiles and glaze batches but I've got workers down there all day today putting in huge hole and sump pump so I don't have to deal with messy towels sopping up buckets of water every time it rains really hard. So in the one run, a good thing. But today... not so good. I guess I'll watch the last video in that glaze making course on Color. Probably the Universe at work yet again. making me do what I should do instead of what I want to do.

Edited by GreyBird
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Mary:

the latest out of the test kiln; more of my early " learning to throw pieces." 

I soaked this bisq piece in water before I glazed. One thing for certain, Hudson is hyper- sensitive to application thickness. Spraying appears to be the only method for true uniformity. Although you could apply in various thickness as you move up the pot to produce color bands.  I have used 1750, 1850, and 1930F as soak holds for iron development. Hematite seems to favor 1930F and up- it develops more into the red side of the spectrum.  7/1 SiAl ratio seems to develop the best overall glaze: landing somewhere just under " high gloss." Satin and matte would be under that: although extended heat soaks will dull it down to some degree. 

You have been studying Seger, so here is the recipe in molar %

Li 10.91  Na 0.70  K 1.48  MGO 2.76  Ca 4.56.   Fe 1.70. Al 8.99. Si 67.49.   Si/AL ratio 7.51. Est. COE 5.77

edit: picture replaced with better quality.

image.jpg.0e5a639b7cff5ecf8d304020a603b6fd.jpg

 

Edited by glazenerd
Picture replaced with better quality.

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4 hours ago, glazenerd said:

Mary:

the latest out of the test kiln; more of my early " learning to throw pieces." 

I soaked this bisq piece in water before I glazed. One thing for certain, Hudson is hyper- sensitive to application thickness. Spraying appears to be the only method for true uniformity. Although you could apply in various thickness as you move up the pot to produce color bands.  I have used 1750, 1850, and 1930F as soak holds for iron development. Hematite seems to favor 1930F and up- it develops more into the red side of the spectrum.  7/1 SiAl ratio seems to develop the best overall glaze: landing somewhere just under " high gloss." Satin and matte would be under that: although extended heat soaks will dull it down to some degree. 

You have been studying Seger, so here is the recipe in molar %

Li 10.91  Na 0.70  K 1.48  MGO 2.76  Ca 4.56.   Fe 1.70. Al 8.99. Si 67.49.   Si/AL ratio 7.51. Est. COE 5.77

edit: picture replaced with better quality.

image.jpg.0e5a639b7cff5ecf8d304020a603b6fd.jpg

 

Whoa, very nice. Would you say that is semi transparent? So is the body white? I wonder what it would do with surface irregularities, like stamping and such and if it would show underglaze painting underneath? Filling out annoying paperwork today. Thank you for this little distraction :)

Edited by GreyBird

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Mary: 

Hudson is especially suited for " breaking" color. The test piece was white stoneware with 8% 20 mesh grog. Those white specks on the outside are grog particles. Look inside the rim where the grog scratched the surface: clear color breaks.

translucency is not the term I would use to describe the optical effects: " bifringence" however is.. Hematite has a unique crystal lattice, creating a unique refractive quality. This piece from page six has some degree of "luster", but again I believe it to be bifringence optics. You can see color shifts around the perimeter and across the bottom.  Part of my testing  is developing  the optical properties of hematite. Just minor variations shift from mahogany below, to an orange spectrum above. Iron " orange" can be developed I believe, an illusive color from oxides.

image.jpg.21c0733caa0bf621e8430552fb1ba4e6.jpg

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On 10/5/2018 at 3:35 AM, Pieter Mostert said:

Mary, Ian Currie published his book on the grid method under a Creative Commons licence, so you can obtain a free electronic copy here.

Hi Peter your link is to Currie’s first book on the topic and not the one to look at if you want to start exploring with his method .  

The book to look at is his second one on the same topic called “Revealing Glazes Using The Grid Method” (has a green cover).  It is MUCH easier reading and much better organized than the first book.  Very practical

Mary if you looked at the first book here no wonder you thought it was not applicable.  

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On 10/4/2018 at 7:03 PM, glazenerd said:

Pieter:

The Hudson slip is the glaze. In Mary's early tests, 78% of the recipe was Hudson: to which 8.4% was iron, more specifically magnetite. So effectively, the brittleness/stress normally associated in a clay body from that % of iron,  is being transferred to a thin coat. One of the gaping holes in clay chemistry is the effects of reduced iron on COE. While a calculator may transfer the iron molarity into the total flux column, it does not accurately project changes in COE. 

While the carbon content is fairly low in this clay as indicated by the 2.35% LOI,  the effects on magnetite specifically is unknown. In addition, the nearly 25% natural flux content results in a COE significantly higher than normally found in a formulated recipe. The COE is in the same range as Frost porcelain: approaching 7%. So that compounds the effects of high iron content. I ran her recipe at 60% Hudson addition, while maintaining the 10% lithium addition: which produced no shivering. One of those rarities that does not fit traditional chemistry.

Tom

 

Hi Tom,  here you mention a 2.35% LOI for Mary’s clay.    This seems very low.  Just wondering where this number came from?

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12 hours ago, glazenerd said:

Curt:

on page one is the chemical analysis: the 2.35% balances known levels.

T

Hi Tom,  the Mineral Analysis Mary provided is on a % Weight Ignited Basis.  This means they have done this analysis AFTER burning to either 750 C or 950 C (which probably explains why there is still so much sulphur left).  The components sum to 100.01%, so there is nothing unaccounted for.   Not sure where your 2.35% is coming from?  In any case, I can confirm that they have definitely not reported an LOI.

Based  on other clay mineral analysis lab results I have seen, I would guess the actual LOI of this clay is something like 7% or 8%, and possibly more depending on how much organic matter it contained.  This would make a big difference if one is plugging this analysis into, say, Insight to play around with glaze formulations.

Edit: As someone said above, this material looks chemistry-wise a lot like Albany Slip, which has an LOI of around 9% to 9.5%.

Edited by curt
Albany Slip reference

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