Hudson River Clay

[curt]

On 8/26/2018 at 3:11 AM, Rockhopper said:

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.

Yes.  You would.    And without that analysis you would be doing it the hard way.  A particle size analysis would also be very helpful to speed you along on clay body development, although you can mostly do that yourself if you have the right sieves. 

But be warned that the costs don’t stop there.  That the exercise is also expensive in terms of time and firing....

...and now you find yourself at the edge of the rabbit hole, peering down, wondering if you should go in.  Don’t worry, the Mad Hatter is in there somewhere....  

[GreyBird]

LOL... too funny, Curt. 

[GreyBird]

Rockhopper,

You could just get the Minerals done for $250. I went for the  Heavy metals because it is the Hudson River and I don't want to poison myself, but from a clean river you should not need that test. Also you could skip the melting point test and figure that out yourself. 

Also, there may even be cheaper ways to get it done. I just did a google search and found this place. But you might contact a university that specializes in Geological studies. I'm sure someone on here could recommend a University program that might be interested in testing a sample for mineral content.

[GreyBird]

Hmmm. So far my shrinkage on the clay from wet to leather hard (feels pretty dry but I expect it can't be fully dry in 24 hours) is only 2.5%. Not at all what I expected. I rolled a 10" coil yesterday (only 1/4" thick ) and left it drying on a slab of plaster. Today it measures 9.75".  It feels very dry but I'm sure it's not completely dry yet as it is a bit cool to the touch. 

Oh, wait, wait, wait... No it measures 9.25" so shrinkage is at 7.5%. Much more reasonable. But still much less than expected.

[GreyBird]

Yes, Bone dry the coil still measured 9.25" So final shrinkage rate is 7.5%. I have some test tiles and some small wheel thrown pieces in a bisque load now.

[GreyBird]

So final shrinkage after bisque is 12.5%. It shrank a LOT in the bisque fire.

[nancylee]

On 8/24/2018 at 11:19 PM, GreyBird said:

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

Would you share where along the Hudson River you found this? I live a mile off the Hudson River, 1/2 hour up past Lake George. The river is very clean up this way, but I haven't noticed any clay deposits. I would love to play with locally found clay!!! 

Nancy

[GreyBird]

Sure, Nancy. I found it just North of Croton Point Park in Croton on Hudson, NY. Pretty much right across from Indian Point! LOL. You should be able to find some nearer to you. Check out this article from the NYS Museum:
http://www.nysm.nysed.gov/research-collections/geology/resources/hudson-river-lake-clay-exposures

 

[nancylee]

On 9/2/2018 at 11:32 AM, GreyBird said:

Sure, Nancy. I found it just North of Croton Point Park in Croton on Hudson, NY. Pretty much right across from Indian Point! LOL. You should be able to find some nearer to you. Check out this article from the NYS Museum:
http://www.nysm.nysed.gov/research-collections/geology/resources/hudson-river-lake-clay-exposures

 

Thank you! Much appreciated! 

[GreyBird]

Here is how it bisqued at 04:

[oldlady]

took me a minute to realize the glaze test tiles were thrown with the foot outwards, the opposite of mine.  ain't clay fun!

[Benzine]

Your clay looks far different, than the found clay that I've used.

 

Your results look quite promising.

[GreyBird]

19 hours ago, oldlady said:

took me a minute to realize the glaze test tiles were thrown with the foot outwards, the opposite of mine.  ain't clay fun!

Mine have feet in front and back

[GreyBird]

4 hours ago, Benzine said:

Your clay looks far different, than the found clay that I've used.

 

Your results look quite promising.

Benzine, Like yours, it is brittle... I would say typical of a low fire earthenware clay. My tiles are thin and I could snap then quite easily if I tried. It does have a nice amount of Iron in it so that along with it's extreme plasticity makes it a bit different. 

[GreyBird]

Well this is interesting... So, I have zero patience so of course I had started my test kiln with the test tiles in it before I got feedback from you all on how to match it's firing schedule to my large kiln's firing with a cone sitter. The general consensus was that it would cool down too quickly which it did. So I'll find my instructions and figure out how to slow down the cool but in the meantime I had made a tile with "Old Gold Albany" using Albany Slip (I have a bucket) and mixed up the same recipe substituting the Hudson clay and called it "Old Gold Hudson". I'm attaching a photo here as they are very different. The "old Gold Albany" came out as expected albeit more glossy because of the rapid cool, but I had expected the "Old Gold Hudson" to be similar if not the same but as you can see.... They are not at all the same  

[Magnolia Mud Research]

Different YES!  WOW!

Both are interesting !  Gold Hudson has potentialin the stamped areas are lighter in color.  Check if the true thickness is thicker.  Try layering Albany over Hudson and Hudson over Albany .  Add some kaolin to Hudson and see what happens 

[glazenerd]

Mary:

congratulations on discovering a new clay to play with. I was expecting a different result, as noted earlier. 

To mimic large kiln: program a cool ramp from peak to 1300F at 300F an hour.   

T

[GreyBird]

3 minutes ago, Magnolia Mud Research said:

Different YES!  WOW!

Both are interesting !  Gold Hudson has potentialin the stamped areas are lighter in color.  Check if the true thickness is thicker.  Try layering Albany over Hudson and Hudson over Albany .  Add some kaolin to Hudson and see what happens 

I will do! First I am going to re fire with the controlled cooling program (tomorrow ) to match my large kiln. I LOVE this little test kiln. I can see testing lots of ideas. I was thinking it might be cool too to add a bit (maybe 1%) Rutile and in another sample adding a small bit of tin or zircopax to lighten it a bit. What do you think the Kaolin will do? One question... what did you mean by "test if the true thickness is thicker"? I know the glaze was applied good and thick. It had a nice heavy cream consistency and I held the tile in the glaze for a count of 10 seconds, then when that dried another quick dunk. 

Thanks!
-Mary

[GreyBird]

10 minutes ago, glazenerd said:

Mary:

congratulations on discovering a new clay to play with. I was expecting a different result, as noted earlier. 

To mimic large kiln: program a cool ramp from peak to 1300F at 300F an hour.   

T

Tom, I think my large kiln cools slower than that. It has 6" walls so the cool down can take forever. I think 175° an hour would be more accurate. Of course next time I do a glaze fire I'll keep track and know exactly... then I'm off tot he races! LOL

[glazenerd]

On August 24, 2018 at 3:44 PM, glazenerd said:

 

 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!

 

 

T

One word of caution about 175F cooling ramp: this rate could promote iron crystals. Not a bad thing, but also dependent upon peak temp. Remember, you are dealing with 8.31% iron levels. For the record, color result is also indicative of hematite as the iron source, and not iron disulfide. ( pyrite). 

Tom

[Magnolia Mud Research]

Mary,

From the picture, both glazes seem to pull from the edges of the stamped areas - a characteristic I call 'breaking'.  The Albany glaze seems to break more than the Hudson.  My point about checking the 'true thickness' has to do with the thickness of the fired glaze, not the applied glaze.  There is some areas on the Hudson that is lighter than the main areas; are these lighter colored areas thinner or thicker than the dark areas.  Knowing that bit of trivia provides insights on application thickness, and how to decorate with physical texture on the surface (stamps, carvings, etc.).  Hudson - in spite of its darkness - may be a glaze similar to the high fire reduction glaze "celadon" which is a super treatment for physical decorative texture. 

My thoughts about adding kaolin or ball clay to the mix is to see if this would either encourage micro-crystals to form (make the glaze more matte) and/or to stiffen the glaze somewhat.  The Rutile, tin, Zircopax, etc are good ideas.  I also suggest you do a line blend with your favorite clear glaze and the Hudson slip.  Several years back a colleague did such a blend with Alberta slip and produced some very stunning combinations for sculptural work.  

I recommend you try the lemon test (see the Mastering Cone 6 Glazes book, and or the book's website for more on the test details) to see if food acids changes the appearance of the glaze.  

Also consider using the Hudson as a source of iron in one of your other favorite glazes just to see what happens.  

LT

 

[GreyBird]

3 minutes ago, Magnolia Mud Research said:

Mary,

From the picture, both glazes seem to pull from the edges of the stamped areas - a characteristic I call 'breaking'.  The Albany glaze seems to break more than the Hudson.  My point about checking the 'true thickness' has to do with the thickness of the fired glaze, not the applied glaze.  There is some areas on the Hudson that is lighter than the main areas; are these lighter colored areas thinner or thicker than the dark areas.  Knowing that bit of trivia provides insights on application thickness, and how to decorate with physical texture on the surface (stamps, carvings, etc.).  Hudson - in spite of its darkness - may be a glaze similar to the high fire reduction glaze "celadon" which is a super treatment for physical decorative texture. 

My thoughts about adding kaolin or ball clay to the mix is to see if this would either encourage micro-crystals to form (make the glaze more matte) and/or to stiffen the glaze somewhat.  The Rutile, tin, Zircopax, etc are good ideas.  I also suggest you do a line blend with your favorite clear glaze and the Hudson slip.  Several years back a colleague did such a blend with Alberta slip and produced some very stunning combinations for sculptural work.  

I recommend you try the lemon test (see the Mastering Cone 6 Glazes book, and or the book's website for more on the test details) to see if food acids changes the appearance of the glaze.  

Also consider using the Hudson as a source of iron in one of your other favorite glazes just to see what happens.  

LT

 

Wonderful, Thank You! I do have that book. I will do the lemon test

[GreyBird]

OK, so another round of test tiles brings me back to the drawing board with both the Hudson and the Albany Glazes. The Albany Gold had originally shivered so I had added 5% potash Feldspar. It looked good after the last batch of test tiles but after a day or two it too shivered. The first Tile I did with Old Gold Hudson still has not shivered but the second firing which mimicked the slower cooling of the large kiln brought out the sheer in that glaze as well... lots of shivering there as you can see in the photo. I had thought it was stable so had done a test with 1% Rutile and another with 1% Tin. Neither of those shivered (yet) but nor are they particularly attractive.

I think it would be good thing to take the online glaze course by Matt Katz that someone had recommended to me so I can better understand how to formulate my own glaze from this clay instead of my current stab in the dark method.

https://www.ceramicmaterialsworkshop.com/about-glaze-calculation-online.html

 

[glazenerd]

Mary:

not so sure this is a straight forward glaze issue. This clay has over 17% total fluxes (molar). In addition, the SiAl ratio is 5.06 - which is off enough to weaken the body.  

T

[GreyBird]

1 minute ago, glazenerd said:

Mary:

not so sure this is a straight forward glaze issue. This clay has over 17% total fluxes (molar). In addition, the SiAl ratio is 5.06 - which is off enough to weaken the body.  

T

I've used it here in a glaze recipe over a stoneware cone 6 clay body. So I guess I'm not sure what you are saying? But I guess that's why I am taking the Glaze course which covers clay bodies as well.