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GreyBird

Hudson River Clay

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So I got the idea to walk along the river and look for naturally occurring clay. I expected to find some gritty stuff that would be a lot of work, but might be fun to experiment with in some glaze recipes. I've attached a video of what I found. I am becoming more and more obsessed with it as I sink my hands in, work it into a slurry and smear it onto a plaster slab. I had already done so with an orange sized sample and the elasticity is truly amazing. Better than any store bought clay I have used. No grit at all. As smooth as butter.

I have until now used my pug mill for reclaim stoneware. But now I'm thinking to use it for river clay and I could always just keep my reclaim to a minimum and pug it into the river clay. It can only make it a little stronger right? If it is in small enough amounts I am thinking (hoping) it will not cause the firing temp to fluctuate too much. My guess is this clay will fire up nicely at 06. I've never really been into low fire but something about this found clay... I just have to use it to make stuff! Sure also in glaze recipes but it's just too clean and awesome to not use to make pottery with on it's own. 

Anyone else have experience with found clay? Any tips, warnings, etc.? I did send a sample off to get the mineral breakdown as well as  heavy metal testing and even melting point. Do you guys know if I can tell vitrification temp from melting point? Is it consistently a certain amount of degrees under melting point?

See the video here... fresh clay from the river bank! https://youtu.be/hPoKkx79KOQ

 

river_clay.JPG

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When I decided to try using my pond clay,  I made a series of small pyramids, aka cones, scaled after regular Orton cones.  I placed these 'test' cones in a holder big enough to catch all the mess if the clay fully melted.   I also placed a pack of regular cones nearby so that I could have a good comparison of my clay with the cones.  As I remember I used the regular cone back we used for the school's cone 10 firing -  cone 06, cone 3, 5, 9, 10, & 11.  My clay was not mature at cone 10, it was more like bisque ware.  


A recent test of some "unknown" tramp clay was tested to see what happens, done the same way,  The clay fully melted at cone 10 and would be useful as a glaze.  

LT

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I do indeed have some experience with found clay.

I was given some, by a Science teacher, at a District I worked at.  She got it from her property, near a Creek (Stream) I believe.  It looked blue green, when I got it, though I  still have some, and it looks less so now.  I ran it through a screen to get rid of a lot of the debris (big rocks, twigs, etc), and let it dry out to a workable consistency.  It actually threw fairly well.  

Even though, I only fired it to cone 04 or 05, I still fired the test tile, on  a scrap piece of my normal clay, just to be safe.  It fired to a nice golden yellow color.  However, both the test tile, and wares I made with it, were quite weak/ brittle.  I would compare it to an underfired body, like a finished Raku clay.  The test tile that I made, which was about a half inch thick, L-shaped piece, was quite easy to snap by hand.    I did glaze the wares I made, with the clay, but they were not meant to be functional.

One of my classmates, in college, brought in a seemingly identical clay, to the studio.  It had the same appearance pre and post bisque firings.  In the college studio, we fired higher, so during the glaze firing, she fired it on a dish, the instructor had her make for it, out of our normal clay.  The found clay did melt quite a bit, during the higher firing.  It didn't completely pool, but really slumped, and became glassy.  

I cannot say, what additives you could add to it, for it to work.  It's going to have to be something you test.  But there are plenty of potters out there, who use locally gathered?, harvested? clay.    In some cases, that is part of the reason people buy those wares.

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Is humus elastic like clay? and Slippery? and does it have the viscosity of clay? because this acts a lot like clay. I can roll a coil and wrap it around my finger 'til the cows come him with no cracking. I'm pretty sure it's clay. I googled humus and it says it's  a topsoil layer of dead plants and such. I'm not sure how one could mistake that for clay found 10' down along the side of a riverbed. What is the humus you are speaking of? What would the differences be? I have a microscope, is there a way I can tell under a microscope? 

I will definitely keep you posted. I should get results sometime during the following week but that's going to be a mineral breakdown how will that differ between clay and humus? Thanks! :) 

Edited by GreyBird

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Three types of humus:  mor, moder, and mull.

mor is basically potting soil or compost. Mull is the same basically, but acidic because it comes from sub tropical rain forest.

Moder is commonly called black or dark brown clay. It has a weak crystalline structure, and is mixed with whatever native soils ( clays) around it. It is the most plastic of all clays: which are rated by CEC ( cation exchange.) Common ball clays run 7-11 CEC, bentonites run 75-150 CEC, and humus tops out at 300 CEC. The very high organic carbon content gives it the black color. It has a sub micron particle structure, which also plays into its plasticity index. The 300 CEC index also means it will hold water for an extended period in comparison to other clay types.

i have not seen chemical analysis on humus, but I would expect to see low alumina ( under 10%), higher calcium levels, and higher silica levels.. Much will depend on the clay types it has mixed with.  Humus will make silly putty look "short." :)

t

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Excellent info. Thank you! So I if it is humus, than I can still use it for glaze recipes but probably not for throwing or hand building as it would not fire up well. Would that be correct? I imagine if it has a lot of organic material that burns out during firing, it would be weak when fired.

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Glazenerd, I got the analysis back!!! But now I'm more confused. I guess one should expect to see Arsenic in most natural clay and dirt but is this 10.9 high? So I don't know if the heavy metals gives me any cause for worry. Also they started the melting point test kind of high 2075 degrees. Not sure why they did it for reduction when I specified I'd be firing in an oxidation atmosphere. Is there any difference in temps for Oxidation and reduction? If it's "softening" at 2120, I'm not sure what that means. I wonder if that's the vitrification point? So many questions. I'm expecting a call back from the lab tomorrow morning. Let me know if there is something else you think I should ask :) The results are in .pdf format. Let me know if you want me to email them. I'll try a screen grab, but may not be too clear.

Screen Shot 2018-08-24 at 4.48.18 PM.png

Screen Shot 2018-08-24 at 4.48.31 PM.png

Edited by GreyBird

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Table 4. Standards and Regulations for Inorganic Arsenic
Agency Focus Level Comments
ACGIH Air-workplace 10 micrograms/m3 Advisory; TLV/TWA¹
NIOSH Air-workplace 2 micrograms/m3 Advisory; 15 minute ceiling limit
OSHA Air-workplace 10 micrograms/m3 Regulation; PEL over 8 hour day
EPA Air-environment NA NA
Water-drinking water 10 parts per billion Regulation; maximum contaminant level in public drinking water supplies
FDA Food 0.5-2 parts per million Regulation; applies to animals treated with veterinary drugs

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Grey:

very unusual, but also very interesting. Sorta wish I had a bag to play with. Note the ASTM (test #); which indicates the exact test used to determine the various levels. You can google each test such as ASTM D-6357, which was used to test for heavy metals. Given the fact that this particular test is used to determine metals in coal, fly ash ( coal by-product) is telling.which suggests to me you either have natural coal seams, coal mines, or coal firing power plant somewhere nearby. Arsenic could also be residual from pesticide use. The chlorine level also suggests that a water treatment plant is upstream somewhere. The data Neil posted is "airborne" particulate levels, which is not exactly applicable in this case. I actually need to find the applicable soil limits for metals.

2120F would be the vitrification point, and 2480F would be liquid ( slumping) point. 

The  alumina level is the same for bentonite; part of the plasticity equation. The calcium, potassium, magnesium, and sodium levels are 4-10 times higher than typical ball clays.( further proof this is humus.) the 8.31% iron(fe03) levels are astounding!!!  Which also suggests part of the dark color is coming from oxidized iron, and not carbons. (Although high levels of carbon are present.)  this high level of iron fired in reduction will greatly affect vitrification temps. Actually surprised the softening point was that high.

the analysis defined the iron as Fe03- hematite and not FeS2 (iron disulfide) this is goods news. The analysis also reported no sulfur, also good news.  If the iron source had been FeS2, that level of iron disulfide would produce the classic bloat burgers. You however have Fe03, which will certainly play into vitrification(firing peaks), but not prone to bloating. So from the analysis, I would say you have a very nice cone 04 clay;  and a possible glaze additive that will produce colors previously unseen. Typical red clays used for terra sig only have 5-7% iron ( disulfide). Most interesting clay indeed!

you have to deal with the organic carbons however: the analysis shows no inorganic carbons ( very good news). I would take several lbs dry, and fire at 108F an hour (slow bisq cycle) up to 1250f , then kiln off. If truly organic, your clay should be a med. to lite grey color. Lots of ventilation required during this burn out firing.

**** need to check applicable levels of arsenic in soil ( not air- borne) before you proceed. Then the amount subject to release during firing... This would be the question I would ask the lab. This is the only concern I have at this point. 

I would also suggest you dig past this deposit into the clay just below it. That layer should also be rich in iron, dark brown color, and high in KnaO, calcium, and highly plastic.

T

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WOW, Thank you so much! I am so very excited to play with this clay... after I find out about the arsenic question of course. I will keep you posted :) I googled applicable levels of arsenic in soil and got back: Natural levels in soils usually range from 1 to 40 mg/kg. so 10 ppm = 10mg/kg which is totally within acceptable quantity right? Of course I will still be asking when I speak to them tomorrow :) 

I think the lab I sent the sample off to may not often test clay content. I used MineralLabs.com and they do a lot of testing on coal. Their clients may be more in the fuel industry. So that may explain the why they used a test that is usually used for coal. They are not anywhere near me. I am in NY They are in KY.

Edited by GreyBird

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Grey:

so my curiosity forced me to look at your clay on a (molar) level. iE: Glazemaster 3.0 

total fluxes: 13.41% molar,  plus the iron. KnaO 4.64% molar.  3.71% iron molar. 5.87% MGO molar. Si/Al ratio: 5.07 

LOI: 2.39 < which means carbon burn out, may not be that big of an issue. est. COE: 6.88 

firing range: 1950 to 2150 max. ( cone 04) typically. 

This clay will absorb fair amounts of water when throwing: more suitable for slab, hand building, slump molds. If thrown, dry as possible, smaller forms.

for cone 6. 60% Hudson clay, 40% EPK hits typical C6 molar specs. ( the iron level makes it unsuitable above C6- brittle) 

T

note: the sulfur content is trioxide, not dioxide: which means it will not reduce the iron in an oxidized kiln. ( more good news)

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I did get some low fire glazes in prep for this to be low fire clay. But hmmm, I should mix a glaze from the clay to use on the clay maybe.  I had started throwing a bowl and it stood up pretty well but I had a fairly large stone in it so that bowl didn't make it and it was the last thing I threw for the day on the wheel. I do love hand building as well so will do that with it too. Have to go get more! 

I'll probably try bisquing it to 04 and glazing at 06. and then mix it 60/40 or visa versa with my stoneware and fire to cone 6. See how that turns out. I'll just experiment with it. Is Glazemaster an App?

Edited by GreyBird

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4 minutes ago, Mark C. said:

Hudson River has had a lot of history of bad things flowing down it the past 70 years. That sample looks cleaner than I would have expected.

Yes, I agree! Should have checked for radioactive isotopes. LOL.

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Grey:

glazemaster is a program written by John Britt and Ron Roy ( clay mode).

this clay already has 4.64% KnaO ( molar), which is a truck,load. Total fluxes 13.41%- Typical cone 6 porcelain is 3.89, and cone 6 stoneware 3.29%. Adding a premix which has even more KnaO could cause problems; especially if Nep Sy has been used as the body flux. Then again, I understand the desire to experiment: I will show you my collection of rabbit holes some day.

typical Si/Al ratio is 4/1, this clay is 5/1. Adding straight kaolin is the easiest way to get the Si/Al in line for C6. 

T

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Grey-

Just a quick correction to Nerd’s latest reply. GlazeMaster was written  by Ron Roy and John Hesselberth, not John Britt. The software website is: http://www.masteringglazes.com/

attn: Tom. Know that you are interested in accuracy, therefore my correction.

Regards,

Fred

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Thank You Glazenerd and Fred! Glazenerd, I would love to see your collection of rabbit holes! I sure will be posting my results here :) Last night, because I couldn't wait, I signed up for Digitalfire's Insight-Live. I'm not sure how to use it though so still have to watch the tutorials. I did enter all the clay ingredients and amounts of each into a "New Glaze" but then didn't know what to do with it. It wasn't obvious, like a button that asks "what's your target Cone" or anything like that so that the program could then make suggestions for what too add to reach your goal. Also there should (Maybe there is) be a "Clay" or "Glaze" option so you know weather you are trying to reach a certain vitrification level or melting point for glaze.

I will at some point 
today check out the Glazemaster program at: http://www.masteringglazes.com/

Thanks again!

Edited by GreyBird
Fingers type faster than brain works.

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thank you, tyler.  i thought it might be albany slip, i used it for a very long time in the 1970s.  one of my first glazes was 288.4% albany plus 82.4% colemanite.  a really nice brown with bluish occasionally.  so new i did not know recipes should add up to 100.  

albany alone was a dark brown glaze used on insulators on phone lines and on lots of dark brown pots.

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Where did you send it for analysis ?  And, if you don't mind, what did it cost ?

I have a bucket of clay I dug from the creek-bed where I grew up.  Experimented with it off & on for 2yrs, trying to get a usable ^6 body (or glaze) from it, by mixing with various combinations of EPK, Feldspar, OM4, and other things that were available to me at a local studio.   Have always wondered, if I had it analyzed, would I be able to use the report as the basis to formulate a successful blend - but never found a place to have it tested.

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