Jump to content
Beggs n Achin

Primitive or local clay?

Recommended Posts

Portland is actually closer, I think bc of traffic.  And in the meantime, I'm burning the useless shelf full.of fun stuff I did.  Smashing thi.gs releives a bit if the frustration. What I don't  understand also... my well is a spring fed well and we have iron water from all the iron here in the ground, and also the creek water here (where the clay was) is also yellow.  And the culprit is aluminum? I know I'm being dumb here, but...  ah well. I have an aunt who offered me her gas kiln, but I had no way to haul the heavy thing home. She lived in Shelton, WA on a creek as well, and dug out clay from the creek and hillside by her house and fired it and glazed it in her kiln. Shelton is very close to the bay, there are oyster beds there and mud flats on the bay that you have to be careful about bc they swallow things. I was hoping to.follow in her stead. She only had the advice to.give me to seive the clay and make the piece as thin as possible. She must have gotten lucky with her clay.  That would be Mason County. 

 

I'm watching this little bowl and cup in the stove glow orange and it's torture. lol

20190301_000711.jpg

Share this post


Link to post
Share on other sites

Alumina is refractory, so it raises the temperature that the clay fires at since it doesn't melt til 3750.  It's part of the clay just like the iron and silica are and give it strength.

Share this post


Link to post
Share on other sites

Hubs was commenting, before I read him this post, that the little piece I had fired that glowed  white/yellow, reminded him of aluminum ore. And he also had read (bc he is the one that reads geology books for fun and rock hounds in our driveway) that the Willapa Hills where we are were a big source of aluminum ore, but that it was "dirty", or impure like our coal. Therefore it was cheaper to get aluminum elsewhere, and now we ship in our coal as well bc it is actually cheaper to ship it in than to pay to process it here. 

Then... I'm reading in this pdf study here (again)  about the brick company that used to be here in Chehalis, and the description of the sample, that sure sounds like what I've got here , pg 186, and it describes them digging it out of the hillside and using it "run of pit" or mixed w more clay or sand to make it less goopy, or less sandy... does that mean they dig it out and used it?  I would be ok with a brick-lookin soap dish, if it didn't break when it absorbed water... My chimney is made from those same bricks, as are a lot of the buildings here.... yet my clay breaks when it gets wet. 

I'm not tryin to argue, I'm just tryin to understand. Hubs just keeps reading the study and giving the same answer: "Our clay is brick clay"  They made bricks at that factory and also drain tile. I did note that they used coal for fuel, however.  It did not specify how long the bricks were fired. 

 

On.pg 176 of the study, 1960 to 2165 degrees is the cone temp range given for the clays that are real close to where I'm at, as well. According to this chart http://www.bigceramicstore.com/info/ceramics/maxcone.html.   Also, the brick factory clay sample , pg 187 is listed as cone range 04 to 8, 1915 to 2212 degrees... per that chart.  I hope I'm doing that right. 

So... I'm looking at this chart from this primitive pottery book... and this page amazingly let me upload it today... and it's fuzzy, doggone it... if I'm reaching a dull red, this primitive pottery book says I'm reaching  at least 1300 (in my wood stove.  I know. Totally unsafe and not designed for that. It's  amazing I'm still alive. lol) but higher than that nc we are goi g into the glowing bright orange stage w the bowls and cups. Only that tiny piece I did went yellow- it was the size of an arrowhead. 

Then I'm reading on this page....       

https://www.ceramics.net/custom-ceramics-manufacturing/technical-firing

alumina fires at 2850- 3100.  So do the temperatures by color in this  old book of mine not apply then? Why would it glow orange and at what temps? Urf....  For reference,  the book is  here-  https://www.amazon.com/Make-Primitive-Pottery-Evard-Gibby/dp/0943604389/ref=mp_s_a_1_1?keywords=primitive+pottery&qid=1551435498&s=books&sr=1-1

Ugh. I need a thermometer. And will get the other ingredients.  And mash things and burn things.  We have about 4   slag piles from where the former owners of our place logged. We have been pulling the sticks from there for firewood, as they are all dry. The water pressure here is not sufficient for me to feel comfortable doing a big burn on those piles and keep it under control so we use it in the house and it is dry and burns HOT. Heats the house very well.  So that's why it gets so hot in that stove. 

I'm rattling on, sorry. Brain is crankin on this problem that exceeds my smartness. Hubs told me I won't  be able to fire this clay and so now I have to. lol 

20190227_124834.jpg

Edited by Beggs n Achin
Spelling

Share this post


Link to post
Share on other sites

Beggs:

your local clay runs from 31 to 42% alumina: I used the median value of 36%. Lewis County clay was specifically tested at 4.32% iron- which is sourced from hematite. Most pottery clay (red or dark) has 5-8% iron (disulfide). The good news about hematite is it will produce deeper iron colors even though there is less of it. However, once you get into the 2100F range; the orange/ red color will darken until it becomes brown.

friend of mine works at a brick mill: I had the pleasure of walking through their 300 foot long tunnel kiln when it was under repairs. Without getting into a lengthy explanation about the differences in brick and stoneware: brick is fired in reduction and is dependent upon sulfides reducing the iron to produce density. Pottery from the 40-50's were actually made from brick recipes; our modern stoneware has its roots in brick/ clay recipes.

The only reason I recommended frit was due to the fact you do not have the means to produce enough heat. Frit begins to melt at 1475F, and it will provide you with pseudo vitrification. If you can get into the 1850-2000F range in the future, then I can recommend other (cheap) additions to get the job done.

Silica melts at 3150F without flux additions, yet it is melted everyday at much lower temperatures. Alumina incorporates into a melt at much lower temps as well: it's all about the fluxes. Yes, a cheap hand held pyrometer would serve you well; it will give you some sense of consistency in firing using your current method. I would also recommend some welders gloves if you are getting your hands that close to an open heat source.

remember it's just clay: and like any glaze it can be manipulated to produce results.

T

Share this post


Link to post
Share on other sites

That is very cool about the brick kiln. The guy who ran the museum here in town knew some information personally about the  brick manufacturer here,  but there was surprisingly little info to be gleaned. He did point us to the place where all of the clay was dug out, which set me goin bc it is the same as ours,  only a mile or two away.  Maybe I can find more at the local library.  There has been little info there too, as far as firing without an actual kiln.  Am finding that these Youtube videos with primitive pottery aren't as simple as it looks lol. Unless they all have really great clay there.  They just find clay, slap it together , and burn it. Then have these wonderful primitive pots that they are carrying around like Joe Nature,  watering their wild harvested plants with it. lol 

The Natives here wintered here and went to the mountains in summer. So they wove watertight baskets as far as I can tell, and did not use the clay here,  except maybe for chinking gaps in the longhouses.

I haven't  thanked you, and everybody that posted here,  for your input.and letting me pick your brains, so thank you. 

Is there a book that explains this alumina ratio thing that I can set down and study foe a while... how to mix recipes or something? Bc at some point I may be able to fire hotter outside or maybe get a kiln- if I have to. lol. Although I shy away from modern ways-learning how to do lost skills is kind of my hobby.  A way to become less dependent in a world that literally could come to a screeching stop economically and technologically.   And won't that change in firing temps mean adjusting the recipe?  The college here teaches throwing a pre-prepared clay, and firing it in a kiln.  In high school my arts and craft teacher dug  ask what else he did to it. 

But anyways, this alumina business. It may be finally sinking into my head, am starting to grasp it. Even though I'm holding another little cup in my hand pulles from the woodstove from.last night that... looks (deceptively) like it's fired. This batch was from the other side of my hill and was seived.  These little cups, I have 3 of them so far that are holding up and I scoop water in my aquaponics  w them for now.  This stuff don't play by the rules

 lol 

 

Urf. Tried to upload its pic amd the page is telli g me I'm only allowed so many mb or somethimg again... Oh well, I guess it's not the end of the world. lol

Share this post


Link to post
Share on other sites

@Beggs n Achin There is no single book that details clay chemistry in specifics that I am aware of.

There are natural clays that are ready to fire straight out of the ground. They have the right flux levels, alumina levels, and silica levels.

To give you a quick review on alumina vs. cone fire. Low fire clays typically only have 15-16% alumina by weight. Compared to the typical ball clays used in pottery which have 26-30% alumina. Kaolin (porcelain) typically runs 37% alumina, with some minor deviations.

A low fire body with 50% red art (15% alumina), 15% talc (no alumina), and 15% silica (no alumina) and 20% ball clay (27%) alumina. Of the entire recipe, there is only 13% alumina. There is a common belief among potters that low fire bodies slump at higher cone fire due to flux levels, that is actually a misrepresentation. Clay typically has a cone value of 32, so like silica and alumina: it takes a lot of flux to get it fluid enough to slump. 

From the low fire premise we come to your native clay. You are firing a native clay with 36 to 40% alumina, 4.32% hematite iron. Unknown, but the natural flux content is minimal given its host mineral is shale. So I added talc, which has high magnesium which melts just above 1500F. I also added frit which begins to melt at 1475F. So if you do not have the heat to fuse this highly refractory native clay, then I will add materials that do melt.

 

@Benzine  I have certainly had my share of flops over the years; part of the learning curve. 

T

Share this post


Link to post
Share on other sites

I'm wondering if I have maybe 2 levels of alumina in the 2 different clay locations on my property then?  Bc I have the one half glazed bowl that made it, I posted at the beginning of this thread, and a bunch if little teacups that made it. There are 2 locations Im working with- 1 is very pure, dug from 3 ft down w a backhoe. That one dries very quickly, grey.  

 

And the other is higher up on the hill, yellow or gray, and that was the stuff I had to seive. More pliable and doesnt dry as fast.  Seems to stay tan in color when it dries, whereas the other has that green tint to it. 

 

This is all very helpful info. I'm learning so much.  It's fascinating.   I've almost burned through all the pieces on the shelf that were not gonna make it anyway

 Just a few pieces left,  a teapot and an oil lamp.  I kinda liked those.  Oh well.  

Share this post


Link to post
Share on other sites

From the report: Lewis County clay has 31-42% alumina, so variations would not surprise me. Usually clay gets more plastic as you move down a hill: the potassium, calcium, and potassium from decaying plant life mixes with ground water and deposits in lower levels. Some deposits are sedimentary, others deposits from when icebergs came across: Ohio, Kentucky, and Tennessee are prime examples. Alumina levels come from the parent material: kaolin often picks up alumina from bauxite or mica. Usually high plasticity ball clays are found next to coal seams: but that also comes at the expense of added lignite coal particles and sulfides. 

That said, in NY hectorite is formed in the high elevations of the mountains from decayed plant life. I received a sample last year: perhaps one of the most plastic and unique materials I have seen. Not impossible for that same scenario in your location. There are many rather cheap ball clays that can be purchased and added to your native clay to correct plastic properties. You have the unique opportunity to work with hematite (iron), which produces colors much richer than the common iron source in most pottery clays. You should be able to produce buff, terra cotta, and browns with little effort. Although your terra cotta color will be deeper than the classic color. All part of the learning curve; you will get there. Enjoy the journey!

Tom

Share this post


Link to post
Share on other sites
On 3/1/2019 at 3:18 AM, Beggs n Achin said:

Hubs was commenting, before I read him this post, that the little piece I had fired that glowed  white/yellow, reminded him of aluminum ore. And he also had read (bc he is the one that reads geology books for fun and rock hounds in our driveway) that the Willapa Hills where we are were a big source of aluminum ore, but that it was "dirty", or impure like our coal. Therefore it was cheaper to get aluminum elsewhere, and now we ship in our coal as well bc it is actually cheaper to ship it in than to pay to process it here. 

Then... I'm reading in this pdf study here (again)  about the brick company that used to be here in Chehalis, and the description of the sample, that sure sounds like what I've got here , pg 186, and it describes them digging it out of the hillside and using it "run of pit" or mixed w more clay or sand to make it less goopy, or less sandy... does that mean they dig it out and used it?  I would be ok with a brick-lookin soap dish, if it didn't break when it absorbed water... My chimney is made from those same bricks, as are a lot of the buildings here.... yet my clay breaks when it gets wet. 

I'm not tryin to argue, I'm just tryin to understand. Hubs just keeps reading the study and giving the same answer: "Our clay is brick clay"  They made bricks at that factory and also drain tile. I did note that they used coal for fuel, however.  It did not specify how long the bricks were fired. 

 

On.pg 176 of the study, 1960 to 2165 degrees is the cone temp range given for the clays that are real close to where I'm at, as well. According to this chart http://www.bigceramicstore.com/info/ceramics/maxcone.html.   Also, the brick factory clay sample , pg 187 is listed as cone range 04 to 8, 1915 to 2212 degrees... per that chart.  I hope I'm doing that right. 

So... I'm looking at this chart from this primitive pottery book... and this page amazingly let me upload it today... and it's fuzzy, doggone it... if I'm reaching a dull red, this primitive pottery book says I'm reaching  at least 1300 (in my wood stove.  I know. Totally unsafe and not designed for that. It's  amazing I'm still alive. lol) but higher than that nc we are goi g into the glowing bright orange stage w the bowls and cups. Only that tiny piece I did went yellow- it was the size of an arrowhead. 

Then I'm reading on this page....       

https://www.ceramics.net/custom-ceramics-manufacturing/technical-firing

alumina fires at 2850- 3100.  So do the temperatures by color in this  old book of mine not apply then? Why would it glow orange and at what temps? Urf....  For reference,  the book is  here-  https://www.amazon.com/Make-Primitive-Pottery-Evard-Gibby/dp/0943604389/ref=mp_s_a_1_1?keywords=primitive+pottery&qid=1551435498&s=books&sr=1-1

Ugh. I need a thermometer. And will get the other ingredients.  And mash things and burn things.  We have about 4   slag piles from where the former owners of our place logged. We have been pulling the sticks from there for firewood, as they are all dry. The water pressure here is not sufficient for me to feel comfortable doing a big burn on those piles and keep it under control so we use it in the house and it is dry and burns HOT. Heats the house very well.  So that's why it gets so hot in that stove. 

I'm rattling on, sorry. Brain is crankin on this problem that exceeds my smartness. Hubs told me I won't  be able to fire this clay and so now I have to. lol 

20190227_124834.jpg

 

On 3/1/2019 at 3:18 AM, Beggs n Achin said:

Hubs was commenting, before I read him this post, that the little piece I had fired that glowed  white/yellow, reminded him of aluminum ore. And he also had read (bc he is the one that reads geology books for fun and rock hounds in our driveway) that the Willapa Hills where we are were a big source of aluminum ore, but that it was "dirty", or impure like our coal. Therefore it was cheaper to get aluminum elsewhere, and now we ship in our coal as well bc it is actually cheaper to ship it in than to pay to process it here. 

Then... I'm reading in this pdf study here (again)  about the brick company that used to be here in Chehalis, and the description of the sample, that sure sounds like what I've got here , pg 186, and it describes them digging it out of the hillside and using it "run of pit" or mixed w more clay or sand to make it less goopy, or less sandy... does that mean they dig it out and used it?  I would be ok with a brick-lookin soap dish, if it didn't break when it absorbed water... My chimney is made from those same bricks, as are a lot of the buildings here.... yet my clay breaks when it gets wet. 

I'm not tryin to argue, I'm just tryin to understand. Hubs just keeps reading the study and giving the same answer: "Our clay is brick clay"  They made bricks at that factory and also drain tile. I did note that they used coal for fuel, however.  It did not specify how long the bricks were fired. 

 

On.pg 176 of the study, 1960 to 2165 degrees is the cone temp range given for the clays that are real close to where I'm at, as well. According to this chart http://www.bigceramicstore.com/info/ceramics/maxcone.html.   Also, the brick factory clay sample , pg 187 is listed as cone range 04 to 8, 1915 to 2212 degrees... per that chart.  I hope I'm doing that right. 

So... I'm looking at this chart from this primitive pottery book... and this page amazingly let me upload it today... and it's fuzzy, doggone it... if I'm reaching a dull red, this primitive pottery book says I'm reaching  at least 1300 (in my wood stove.  I know. Totally unsafe and not designed for that. It's  amazing I'm still alive. lol) but higher than that nc we are goi g into the glowing bright orange stage w the bowls and cups. Only that tiny piece I did went yellow- it was the size of an arrowhead. 

Then I'm reading on this page....       

https://www.ceramics.net/custom-ceramics-manufacturing/technical-firing

alumina fires at 2850- 3100.  So do the temperatures by color in this  old book of mine not apply then? Why would it glow orange and at what temps? Urf....  For reference,  the book is  here-  https://www.amazon.com/Make-Primitive-Pottery-Evard-Gibby/dp/0943604389/ref=mp_s_a_1_1?keywords=primitive+pottery&qid=1551435498&s=books&sr=1-1

Ugh. I need a thermometer. And will get the other ingredients.  And mash things and burn things.  We have about 4   slag piles from where the former owners of our place logged. We have been pulling the sticks from there for firewood, as they are all dry. The water pressure here is not sufficient for me to feel comfortable doing a big burn on those piles and keep it under control so we use it in the house and it is dry and burns HOT. Heats the house very well.  So that's why it gets so hot in that stove. 

I'm rattling on, sorry. Brain is crankin on this problem that exceeds my smartness. Hubs told me I won't  be able to fire this clay and so now I have to. lol 

20190227_124834.jpg

I wouldn't buy anything written by McPherson,  not sure about Gibbys book, but have doubts...I have Simpson's book,(It won't help) ... I like Hal Rieggers book "Primitive Pottery ".  

Alabama

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.