Jump to content
Beggs n Achin

Primitive or local clay?

Recommended Posts

 

I do not have a kiln and really don't want to get one. I'm aiming for primitive skills.  My ancestors did it, so can I.

I am new to pottery. Only worked with clay in high school, so now, 20 years later.  But even then, my art teacher dug up local, brown clay from the Chehalis River basin in Western Washington.  I have fired little beads and things  successfully in my woodstove in the house with the local brown clay.  Also did a lot.of.cob in my old hpuse.and built a fire pit and fireplace surround with cob (clay, sand, straw mixture)

So I moved to a new place and it is LOADED with grey and yellow clay (the brown stuff cracked badly while drying and also disentegrated when firing, so I abandoned that- too much organic matter?  It came from the bottom dip on my field and passed the "snake" test, and was fine and soft, nice to work with and no rocks- which is why now, in winter my field is a mud mess  and I have been trying to pit fire or fire in my woodstove.  Note- my goal is to do things primitively.  Eventually, it may be a side hustle for the farm. But for now I am just aiming to make some coffee cups and a few bowls to eat my Cheerios from. Yes, I have read about the food safety rules.  I'm still gonna eat my Cheerios in the bowl. 

So far, my 3 ft hole that I dug as a pit outside has turnes into orange terra cotta from the fires.  I followed the pit fire methods used in Mexico.and by the Natives, found.viseos on Youtube.  Infired the pieces also in the woodstove. Both methods, I made that stuff glow orange. Don't have a thermometer yet, but it's on my list.  Have to buy hay first for the cow. I have fired several cups and bowls and they "ting" when you tap on them, appearing to be completely fired, but then a cup handle will break off when I pick it up, or I fill it with water and let it set for an hour, come back and pick up the cup/bowl and it breaks off in my hand.  The smome turns them black. Or the heat makes them look lime terra cotta.  I even had one turn terra cotta  color on the inside wherr it broke off, but it still broke off.   I have sort of successfully fired ONE bowl. a d that was in the wood atove, after 4 or 5 firings. I tried a clear, low fire glaze on it and it has little bubbles in the glaze, and unevenly heated, sp only half the bowl is shiny.  I gave up glazing completely for now.  I'm not even burnishing, bc I started making cracks in the piece as I was burnishing it and that was irritating.  

Our ground here is very high in iron oxide, and there is clay everywhere, dotted with red and orange opaque agates and lots of little white  quartzite pebbles.  The well is very hard water and turns everything in the house orange and tastes like iron, as well as the creek water is yellow from the same. Hubs said there is a lot of basalt rock here as well, but mostly just mud. 9

If this clay passes the snake test, and forms nicely and dries nicely... is it not suitable for firing?  

 

I snapped a pic od the bowl that made it, first pic.  And 2 of them that the handles broke off.  Am havin g problems with file size?   Maybe in replies I can get the second part. 

15474518774951875169685347227497.jpg

Share this post


Link to post
Share on other sites

3 of the cups fired outside that handles broke off of.  This camera isnt showing how orange these things are. They are a very terra.cotta.color.   

 

The shiny howl in the original post was fired in the woodstove inside and did better.  Note, that it was windy and rainy in December when I tried to fire outside.  It made a smoky fire and I rhonk it didnt get as hot, but I think the oitside fire heats more evenly bc it is down in the ground 3 ft. 

 

I have one more piece I'm re-firing in the woodstove right now w no glaze that was part of that batch that handles were breaking off of.  It jas been glowing bright orange for an hoir or so now. That's  gotta do something, right? 

 

Anybody have any tips? 

 

15474520992268397814244537498937.jpg

Share this post


Link to post
Share on other sites

3 of the cups fired outside that handles broke off of.  This camera isnt showing how orange these things are. They are a very terra.cotta.color.   

 

The shiny howl in the original post was fired in the woodstove inside and did better.  Note, that it was windy and rainy in December when I tried to fire outside.  It made a smoky fire and I rhonk it didnt get as hot, but I think the oitside fire heats more evenly bc it is down in the ground 3 ft. 

 

I have one more piece I'm re-firing in the woodstove right now w no glaze that was part of that batch that handles were breaking off of.  It jas been glowing bright orange for an hoir or so now. That's  gotta do something, right? 

 

Anybody have any tips? 

 

Share this post


Link to post
Share on other sites

Not all clays will work in a pit or wood stove firing, and anything you fire will weep water.  Could try getting the fire hotter, I think your ancestors probably still made kilns out of clay even if they were just temporary mud ones.  You can see examples of that on the primitive technology channel on YouTube.  It doesn't mean your local clay will work, but you won't know til you get it hotter.  Those look slightly bisqued, so going higher I think will give good results.

 

You're on the right track though that bowl looks like it self-glazed a bit, a little bloating too, oncw you find that perfect temperature you can take note of how they look and fire to the same color each time

Edited by liambesaw

Share this post


Link to post
Share on other sites

That was a clear, low fire glaze, one of my first bowls.  I have been watching all the primitive pottery videos all over Youtube. I think I'm really close to getting it, and I think you are right about the temps.  The mud kiln outside that I built  was too big, I think.  I had the fire to far down in the ground to the pottery up above it.  There is one video where the guy builds a cylinder,  basically a rocket drive out of mud.   I was going for that kind of, and I got the temps at first, but it was very hard to build the fire down in that pit and keep the heat in.   It was a skinny,  deep pit  vs a wide shallow pit. Our weather was very blustery and rainy at the time and I thought that would help with losing heat, but it did not, and the rain melted my clay kiln faster than it could fire... Can't put a tarp over something that is still burning.

I'm still limping along with my current wood stove inside the house, but it's obvious it's not quite getting up to kiln temps. Almost,  but not quite.  I put in a cup made from a low fire clay from Joanns craft store last night that was from Texas... It again, glowed nice and red.  Half completed the clear glaze I had on it, but uneven heating. And it broke badly. Sigh... The broken pieces showed that I got that one to terra cotta stage, however, unlike my local clay, which only seems to not quite terra cotta but mostly bisque.  At least inside. I have tongo put and rework that outside kiln, maybe go smaller, like the video.   My pit outside is 3 ft across, as well.   One advantage I had firing in my house woodstove before at my last hoise was that I had built a cob surround with 4 inches of insulating clay around the wood stove. Not so at this new house.  So that's probably why I can't seem to get the temps.  It is a newer woodstove, as well, designed to not get hotter like the older ones did so it doesnt burn down your house.  I should follow the rules better. 

 

I did find a pdf file about our local clay here in WA w testing and cone temps and it says this clay is only good for making bricks. https://www.google.com/url?sa=t&source=web&rct=j&url=http://www.dnr.wa.gov/Publications/ger_b24_clay_shales_wa_1.pdf&ved=2ahUKEwi5hpCh6fLfAhXMJt8KHdXXAUUQFjAJegQIBxAB&usg=AOvVaw2qzUrkj9BecVPni4eR02O2

I'm not sure how I'm able to get such plastic, workable,  fine clay out of only brick clay.  I'm up in my craft room making thin walled little cups less than a 1/4 inch thick.  Seems to me that brick clay would fall apart at that thickness, but I'm a noob and I know nothing. 

 

Last night's fooling around w the local clay.  An oil lamp, and a little cup.  Experimenting how thin I can make it.  

I don't  even glaze anymore until I can figure out how to fire it to terra cotta. Then I will fire again and glaze.  This local clay has a lot of iron. 

20190115_233140.jpg

Share this post


Link to post
Share on other sites

Do not use glazes in the pit. They probably won't get hot enough to melt properly, and will make a mess if the pit material gets on them. The reason things are breaking and handles are coming off is probably due to heating too quickly. You can't just light it up and let it rip. You have to heat them slowly and evenly, which is really difficult to do in a pit. That's why most people who pit fire nowadays bisque fire the pieces in an electric kiln first. But that doesn't mean you can't do it.  Native American potters mix a lot of sand with their clay to improve its chances of surviving, and even the the loss rate is high by modern standards. Since you've got all that clay on your property, you may want to play with building a little tube kiln into the ground, like a tiny anagama. Mix a bunch of organic material into the clay and you'll have a nice castable material to build with. It would still be very primitive, but would give you more control than a pit. You would be able to heat it up more slowly by starting the fire outside the tube, and gradually moving it into the tube. It's basically just a semi-horizontal chimney with pots in it.

Share this post


Link to post
Share on other sites

Passing the snake test and forming nicely does not a quality clay body make.

The snake test is basically a test of the clay's plasticity; plasticity is a combination of particle size and water content. The smaller the sizes the more plastic, and the more water the more plastic a clay. I can add water to just about any singular clay (not clay dug from earth, but a refined clay, sold in bags, like EPK), and enough water will allow me to roll out a snake and form with it, but it will never be a suitable clay body for anything other than looking at.

The other thing about plasticity, is that the more plastic a clay, the more it shrinks, and this also is directly related to how much of a tendency it will have to crack.

A clay BODY, which is what is sold in bags/boxes at your local clay supplier is a combination of different clays and materials designed for an optimum working method. Even clays which are dug from the earth and used must be processed, and often times, more so than just removing sediments and gravel/etc. A local potter here digs his own clay from a cut in a highway, and he adds plenty of materials to it, to make it into a suitable utilitarian clay body.

More testing and altering of your local clay may produce a clay body which will be "usable" in the sense that it will not fall apart when you pick it up, but without some kind of vitreous slip, it will likely never be able to hold a liquid without absorbing it (which would be mighty nasty if the milk turns into cheese in the walls of your pots)

A wood stove will have temps ranging from 500-1200 degrees. Much too low for any regular bisque temps. To achieve temps closer to 1800 deg your going to need to insulate and trap that heat; wood stoves are designed to expel heat, not trap it. Many pit firings are chambers which are sealed over with clay once the fire has gotten to a certain point. The earthen chamber, and sealing of the chamber traps the heat, which will build, getting you closer to a bisque temp. Many farms built their homes back in the day with bricks that were made on site; those bricks were fired in a kiln made from the same clay which was fired in a pit first, and then fully fired in their initial firings of the kilns.

"A ting" when you rap the pot with your knuckle does not necessarily indicate that it has been fully fired; if the pot is fully vitrified (good for food) it will ring like a bell. My bisqueware, which is in no way food safe does have a "ting" to it too. Most clays that are dug from the earth have too much iron in them to become fully vitrified.

The one pot, in the middle, where the handle broke off, shows what could be iron coring; could be caused by ecessive iron contents, or a lack of oxygen during your bisque. This is generally thought of as a fault, and does weaken the pot.

I dont want you to mistake what I am saying as a sign that you shouldnt continue doing what you're doing, but do be aware that ignoring food safety issues is your own liability, and you should not subject anyone else to it until you've thoroughly tested the materials and process. Making pots from local, hand dug clay, and fired in your yard is fun, and informative, just use that information wisely!
Best of luck!

 

Share this post


Link to post
Share on other sites

I'm breaking off the cup handles when I am done firing them, or I moved a piece of wood around.  So it will look like it's done, I pull it out.of the now cool woodstove, and the handle  breaks off.  

Ya, this woodstove isn't gonna do it.  Sigh...  Have to build fence before I can build a kiln again- this time, no pit.  Too many breaking things involved in that pit.  But I'm close, I know if I can get that heat, I will have a primitive form of pottery, and then I can improve  from there.  I'm actually ok with imperfections at this point, going for the whole primitive thing. 

 

All this info is very helpful, thank you. Our local college here only does manufactured clay classes with a kiln, and the pottery shop here ships in premade pottery for painting.

Edited by Beggs n Achin
Spelling

Share this post


Link to post
Share on other sites
5 hours ago, Beggs n Achin said:

Too many breaking things involved in that pit.  But I'm close, I know if I can get that heat, I will have a primitive form of pottery, and then I can improve  from there. 

Pits come in all kinds of shapes and sizes, from a simple depression in the earth which gets covered over with clay/soil at a certain time, to a brick lined hole in the earth, which gets covered over with sheet metal and fiber insulation.

A small kiln, made from your local clay, will be more work, but will last longer, and will be the cheapest option of them all. You could make it by forming bricks, and stacking the bricks like you would a house, or you could make a form, and basically make a castable kiln. The castable wont last as long as a brick made kiln, because there is no room for the kiln to expand/contract (bricks slide a little as they expand), but it would be the easiest.

You could make a form using scrap wood/materials, basically a box with an arch on top, place it on the earth (or better yet, on a clay base), and pack your local clay (mixed with sand, straw, etc) around the form until you have 6" or more of walls. You'll have to build in some kind of a firebox, and a chimney (keep it simple and just do a updraft kiln), and some way to seal the opening shut (clay bricks which are "mudded" closed for each firing). Remove your form(design your form so it will "collapse" inwards, making it easy to remove) when the clay is firm enough to hold its own shape, let it dry for a week or more (depending on climate), and then build a small fire inside, gradually increasing the heat until you have "fired" your kiln. From there it'd be ready to use. You'll need to keep water off it; a trash can could be placed on top (if its small enough), or maybe make a small, dog house like structure that you can easily move with 1-2 persons.

Not a guarantee that this kiln could reach mid range(more possible), or high(less likely) fired temps, but its possible that it could with stand the temperatures. Id imagine maybe a pallet (literally the pallet) or two of nice dried oak will get you to bisque temps (if the kiln chamber is 2 cu/ft or less). A lot of this depends on how you stoke your kiln, and the design (chamber size in relation to chimney size/height, primary air, secondary air......lots goes into designing an efficient kiln, and firing with wood is an art form unto itself).
If you can get the proper heat, you will be on your way to eliminating the issues with your clay, and finding the right ratios of additives to make a "usable" clay body. Some research into vitreous slips (which can be made from soils found at creeks/rivers) and more testing may provide you with a native material which could be "food" safe (to an extent).

Share this post


Link to post
Share on other sites

Reaching low fire/pit temps can be done with just about any cobbled up kiln shaped thing with a firebox and a flue. A little more engineering and you'll be able to get to mid range temps or higher. The limit would be how hot your clay can stand to go. A castable material made from your clay mixed with organic material- flour, straw, rice, coffee grounds, etc, will insulate better and withstand the expansion and contraction from the heat. If you do a tunnel/tube, you can bury it for greater insulation. Here's a very rough photo of a primitive tube kiln, set into a hillside. I'd slope the floor more, but you get the idea. In the old days, they were literally just dug out of the hill. You could easily build a version of it by just piling up soil and lining it with clay.

 

Tunnel-Kiln.jpg

Share this post


Link to post
Share on other sites

Begs:

looking at your second unfired piece: there are obvious large particles in your clay. Need to start with some processing: sieving dry clay through an 80 mesh screen would help. You have plenty of iron to produce terra cotta: just need more heat. Get up in the 04-02 range and  the terra cotta will deepen. Adding 15% talc would help: talc will help control thermal expansion/thermal shock issues. The dark grey/black are both carbon (ash) issues: although magnesium can produce those colors. There are ways to control plasticity: rather increasing or decreasing those levels. You have a workable clay: just need to address the deficiencies.

Tom

Share this post


Link to post
Share on other sites

Interesting..    I'm still rollin stuff around in my brain now... lol I need to be.done building cow fence and get back to clay. lol I will never be done w fence.  13 acres of fence w cross fencing....ugh. 

 

Ok, about the kiln idea up here  in the hillside or kiln built w dirt, tube kiln... Let me attach a couple pictures, see if I was close, bc I think I may have been (has since been torn down and is now just a fire pit for bc it was reduced to a collapsed mud pile while on fire, during one rainstorm- it rains sheets of rain sideways, here) - yes, its ugly as sin. 

I had mentioned above we had tried this kiln thing, and the weather attacked it before I could get it to fire pottery. Or finish firing itself. It got hardened, I could punch it with my fist,  but then the rain was right back at it. Sigh... Couldn't get hot enough, heat was being used up  keeping the actual kiln itself dry.  But I haven't given up on that bad boy yet, just throwing a cup in the woodstove for now once in a while w wishful thinking, since I'm burning the wood anyways.  And it IS wishful thinking. I pulled out another cup this morning that was nice and orange on the outside, but I know on the inside it is barely bisqued...  and I saw it glowing nicely red all over. It's  frustrating to see that...

And I have 2 batches of clay that was screened, evaporating the water out in front of the wood stove. 

First pic hete is the mud/straw kiln over top that 3 ft deep pit.  Not finished yet in the pic, but I had a good 4 to 6 inches thick all over on the sides, a little thinner on top, and that wire supported it.  Pieces sitting on the  metal rack. 

 Second pic is that sketch that was posted up above, here,  that I drew on to try to explain what that kiln was, bc it looks very close to what was described here.  It had several issues aside from all the blasted rain and wind here.  If that is close, then I won't start a brand new one, but will rebuild that one to be better. 

Problems with it were... 3 ft pit underneath it.  It got plenty hot, the shiny, half glazed bowl in the above pics... came from that fire.  I made terra cotta all the way through in that pit.  

Pieces were on a rack 3 ft above the fire w the wind howling  in around the sheet metal I plugged the front with.  

Back smoking really bad out the front,  and very little going up the chimney.  Also, when I blocked up the front with mud globs, it made the fire die out. 

The fire was kind of like this pic,  which also resembles a Dakota fire, and also a rocket stove.  All these are kind of the same shape and same idea.  A Dakota fire is a hole dug in the ground to protect it from wind, w an air inlet hole dug out sideways to feed it. 

 

We also dug a smaller, shallow pit beside this one, put a saggar (big terra cotta flower pot) over the piece, and covered it all w sheet metal to protect from the weather, coals and fire all over the thing...   It broke the saggar... didn't fire the piece. Lots of smoke, lots of struggling with weather. Urf.  I tore that one down and challed it up.as another failure after 3 tries. 

So I have filled in the 3 ft hole in this pictured firepit here, and now I'm gonna just do a vertical tube upward from the ground, probly w fire brick bc it won't  melt... and hu s is tires.of messin w mud.  He was belly achin the whole time jow it was gonna fail, anyways.  I will keep the existing rack in there, and have my fire up closer to the rack.   And mud in bricks at  the front opening, hoping the fire wont die when I  cut off the air.  That hole is also about 3 ft wide, too.  The weather is behaving a little better after December. We get clear, calm days now, instead of mini hurricanes.   I tarp the thing when it's not hot.   Someday will have a pretty gazebo there to roast marshmallows in. Someday. After the fence.

Screenshot_20190118-083144_Chrome.jpg

20190118_082331.jpg

Edited by Beggs n Achin
Typos.

Share this post


Link to post
Share on other sites

I was thinking this design on my existing firepit.  Similar to what I already had going, but more vertical

  It seems the idea is to close off the area where pottery is, but do not close off the fire.  Is this correct?    This also seems like this fire would need a lot of ongoing babysitting, shoving little sticks in there every hour.   And these primitive pottery videos don't tell you how long to leave the stuff in the fire.  The Natives and their pit fires lasted a whole day into the night, but this setup is more like a rocket stove, that gets much higher temps bc of its really good air flow at the bottom .  

I have actually built a  little 2 ft tall clay rocket stove in my kitchen once and vented out the window (the stove broke and we were broke, too).  It was 4 inches wide or so... I cooked dinner in a cast iron skillet on top of it, using nothing but little twigs.  Note to self: Use bone dry wood, unleas ypu lime smoke.  Yuck.  They call it a rocket stove bc the terrific draft and using small sticks creates a flame shooting up out of the top that looks like a rocket. Very hot, efficient  fire. 

 

  

 

Edited by Beggs n Achin
Typos.

Share this post


Link to post
Share on other sites

Sheet metal and metal rack might not be a good idea once you get up around bisque temps.  I have a fiber kiln and where there are gaps in the insulating material it straight up burns the sheet metal reflectors back.  These are temperatures that are unfriendly to metal.  You can just build a shelf out of clay that is above and behind the stoking area but in front of the flue.  Think of the wood burning and the heat escaping from the chimney, you want the pots between those two points

Share this post


Link to post
Share on other sites

Admiring your determination. Hope you have better results with better weather. 

Note: a strong draft may be emptying the  kiln of heat before it can build up. A damper on the exit flue will offer more control.

Share this post


Link to post
Share on other sites

What you built looks more like a kiln and less like a pit to me. You are on the right track with what you did. I would make the chamber smaller and put the firebox in front of and leading into the kiln. The kiln chamber should be big enough for you to fire maybe 4-8 pots; what you had is MUCH too big to be learning with and will make it harder to control/learn from. As you get a handle on the firing process, you can make a larger kiln, tweaking it based upon your learned experiences. Omit the wire rack, and maybe make the chimney a little taller. Like Liambesaw said; you can make "shelves" from clay, but traditionally most pit fired pots are tumble stacked. A bed of clay on the ground will work well enough.

The wire in your arch can stay, but I would keep it in the outer 25% of the walls thickness; not that this kiln will be getting to mid range or higher temps, but steel will begin to oxidize and degrade rapidly with heat even at lower temps. If the wire IS the only thing keeping the arch together, you dont want to compromise the integrity of the kiln, during the firing, so best to keep it cooler, than hotter.

You might ask around to see if any local potters have old soft bricks laying around that they dont want anymore; crushing these up into pea-walnut sized chunks, and adding them into your clay mix will help retain heat. Wear a respirator while breaking the bricks up; the dust is not good for you at all!

You need  three things for  combustion ;fuel source, heat, and oxygen. Firing with wood is not like heating with a wood stove. It does require relatively constant feeding of smaller pieces of wood. Dumping a pile on and lighting it will yield less btu's/temperature than if you fed the fire the same amount of wood in small stages. If your firing is fuel rich, it will stall in temp. This is also why you don't want to close off the firebox as you will starve the fire of oxygen; there has to be a nice balance. The opening for your firebox should be about the same as your flue size. If the chimney is bigger it's better as you can use a damper on the chimney to control the air intake. The chimney should also be at the far back of the kiln chamber, this will help pull the heat all the way to the back, minimizing cold zones. Some old roofing metal can keep your kiln dry during use, but no kiln likes to be wet. Keep em dry all the time. Galvanized or painted steel will give off toxic fumes if it is heated high enough, so dont huff the fumes!

The smoke pouring out the front of the kiln is happening because there is not enough draw. For the size of that chamber your chimney is highly anemic.  More draw, less smoke, more heat. If you have a lot of wind, which comes in from a regular direction, consider facing the firebox opening towards the wind; the extra oxygen and "bellows" action from the wind will give you hotter temps. if its SO much wind, that it is making a fire difficult to control, face it away from the prevailing direction.

" I pulled out another cup this morning that was nice and orange on the outside, but I know on the inside it is barely bisqued ". Unless you have REALLY thick work (like numerous inches thick) it is unlikely that the outside would be bisqued and the inside not; The coloration on the outside is more related to the fire/fuel interacting with the minerals in your clay and fumes/ash from the fire itself. Bisque means that the wares have been fired to a point where the clay is no longer able to be slaked back into mud and reused; essentially it has formed a crystalline structure, it has nothing to do with colors formed on the pot

The terra cotta flower pot saggar probably broke due to too much heat, too quickly. Earthenware does handle thermal shock better than other clay bodies, but very few refractories or clays that potters generally use like rapid heating. Try a thicker vessel, and increasing your temp slower or more evenly across the pot.

Edited by hitchmss
spelling, grammar, info

Share this post


Link to post
Share on other sites

Ok, an update.  Maybe y'all can let me pick yer brain some more. 

 

Pictured below is the brick kiln I started working on. There is some fire brick in there at the bottom, but that got expensive quick, hence the red bricks. I figured.... my 100 yr old house chimney is red brick and it's been doin fine for 100 years....?  40 cents is a lot easier to replace than $2 and a half each.  This kiln is much smaller, as suggested above.  BUT it still needs reworked bc apparently the burn chamber where I put the wood is too tiny and needs more air flow. It's snowing right now so... that project is on hold again. 

 

Meanwhile, back inside with the wood stove.  I know. I'm stubborn. It's warmer inside. lol. So... I have a whole shelf of (ware?- learning terminology) I made up, of what you see in the thread above. Probly gonna blow up.  It was the batch I dug from the ground and picked thepugh it w my fingers, amd them wedged it down and worked with it. I was impatient, and now. I'm payin that piper for it. lol. Little pebbles in there, I want to say half the size of a lentil seed... not as small as sand... exploding. Not all of them. Fired pieces still show little quartzite chunks and the occassional basalt type thing in there.  But some.of it has survived. 

 

So I went back to that same place and dug up some more, mixed it with a drill and paint mixer, let it set in front of the wood stove a few weeks in a bucket, then wedged it and mixed in about 10 percent or so of temper or grog, which consisted of smashed up, old fired pieces of the same clay that didn't make it.  I made a few pieces w that, and fired them in my wood stove again, and that is the soap dish pictured here.  When tapped, it makea that distinctive "chink" sound, just like the red bricks I bought at Home Depot to make my outside kiln.  I left the piece in water overnight, and it didn't  break, dissolve, or leak. 

 

So I'm having "some" success using the indoors wood stove, using the same clay I sieves and processed more.  I'm also usi g a saggar that is one of the first bowls I made of the stuff that had little rocks in it. It is a little u der half an inch thick vs the pieces I put in it, which were 1/4" or less thick.  One pendant, I stuffed it in the hot coals and fire and at one point it went past glowing orange, red, to yellow/white- then I removes it with tongs and it cooled quickly to orange and then dull red again. 

Also, I found another, what looks like more pure, clay deposit on the other side of my property, also on a hillside... Grey, lovely clay. 3 ft down. A backhoe unearthed it when hubs was replacing water pipe. I (impatient again) grabbed some and worked it without sieving it, and fired up some atuff with it right away in the wood stove. It dries REALLY fast, like a more kaolinite clay would, but looks like the stuff I have already been working with, and fires to a terra cotta color.  That was the stuff that glowed yellow/white. Looked like a metal foundry or glass blowing. lol  Huns swears this purer stuff is bentonite... near as I can tell, our geology here would give us a (Schmechtite? Spelling...) clay, of which bentonite is one kind. Hubs is the geology guy. I'm reading a study put put in conjuncrion w the state and the mining industry in 1941 and trying to figure out all of these terms and numbers.  The study says pur clay banks are alluvial, put here by the omd river bank now far from here. 

I mention the color in firing, bc my folks found me 2 books on Amazon about primitive pottery, and one of them lists a chart w the colors if the pottery when it is cooking, gives an approximate temperature range, and what chemical changes are going on at that time. I actually found that very useful. I think... Also useful, was the information, that in primitive pottery, the actual firing process can take as little as 20 minutes. 

 

It's kind of surreal to me, and fascinating, and I am dying to know why... a cup will not fire one time, and I can take the same clay and seive it, and it will fire and make at least terra cotta or brick-like something, that is tough and durable, lightweight, and I can hold a cup of water in it.   That just trips me out. lol 

I have also gotten the process down where I heat the wares up on top of the wood stove in a metal bowl sitting on a metal trivet (so it is not in direct contact w the metal stovetop and crack), until it is too hot to touch. Then I take gloves and metal tool and put either the saggar w small pieces in it, or the coffee cup I had warming... into the coals in the fire and add more small pieces on top.  Ironically, the saggar has been through several fires now and still... it makes the dead thunk and no "chink" sound. And I can tell by pushing on it that it wouldn't take much to break it, too. I have a failed coffee cup in the same condition setting in my kitchen sink right now, too... leaking water everywhere. It's weak and will break... yet I grabbed it out of the fire by its cracked handle. 

 Same clay. More rocks. I don't get it.  

But I'm getting somewhere. 

 

We visited the local historical museum today as well. I was looking at Native artifacts, looking for evidence that they used the clays in this area and found only woven baskets, and tools made from rock.  Apparently, they coomed with hot rocks placed in baskets or wooden boxes of water...not clay pots.  I also found what I had read about this area, historically, that a brick making factory was here, and there were samples of bricks from several of the historical writings, one very early one written with directional markers on it in Chinese.   So the white man used the clay here for bricks. The Natives,  maybe not so much. But they were nomadic and moved back.and forth between the mountains and here. Baskets would have been lighter to transport than clay. 

Urf. So the search continues.  So.far I have a very nice soap dish, a couple Asian teacup type things,  and some pendants and beads.  That have not cracked and/or refused to fire. 

 

 

 

 

20190227_155942.jpg

Share this post


Link to post
Share on other sites

K, having technical difficulties. It is only allowing me to upload one picture. Ever. In any posts. Or the whole page. 

 

If you are really bored, I have been uploading pics to my farm.blog.page. 

fb.me/pleasantvalleyroadchehalis

 

And I have a very long, boring video on Youtube regarding my last firing at 

 

 

And if this is all just too neurotic.and self absorbed... y'all gotta tell me, bc I'm just.over here dissectimg stuff w my brain and I won't  even know if y'all think I'm an idiot bc... I'm still tryin research and learn stuff. lol 

Share this post


Link to post
Share on other sites

Beggs:

you referenced a geological study done on local clays? Do you have a link?

from what little info given, and your location, and the fired color-

Washington is one of the very few places were laterite clay can be found in the States. If so, it would explain the deeper iron color I am seeing in the fired pieces due to hematite iron source. The green color can come from calcium hectorite, or it can come from chlorite clay minerals. Those levels would be on the low side; hectorite is highly plastic and you would not have the dry crack issues. I think the reason it is drying so fast that this clay is high in sesquioxides and lower in clay and clay content. Assumptions at this point based on info provided. 

Tom

 

Share this post


Link to post
Share on other sites

Link to.study.  It is Lewis County, if that helps.  


https://www.google.com/url?sa=t&source=web&rct=j&url=http://www.dnr.wa.gov/Publications/ger_b24_clay_shales_wa_1.pdf&ved=2ahUKEwjk56nnr93gAhVVpZ4KHT7SDAAQFjACegQIARAB&usg=AOvVaw2qzUrkj9BecVPni4eR02O2&cshid=1551320749011

 

I think the green color is lighting. That clay is kind.of.tan, brown, or yellow to orange due to iron. The stuff deep in the ground is all grey and dries really fast. 

 

And disregard my gloating aboit finally firi g a.puece. I just broke my stupid soap dish.  It just took a while.of bei g wxposed.tomwater this time before it weakened. It looms like a brick. Sounds like a brick...  Urfh. 

Share this post


Link to post
Share on other sites

Lewis County is primarily shale, with some mica.

Iron is from hematite 4.32%. Alumina averages 36%, so it is a sesquoxide. Water of Plasticity (WOPL) 29.3%. Dry Shrinkage 4.2%

The green cast is coming from shale, and this is a low plasticity clay.

mix 50% of your local clay, 15% talc, 15% OM4 ball clay,  20% frit ( pick one)  this should produce a workable body. The only reason frit is added is to keep it from crumbling. This is not a workable body on its own- sorry. After you mix it, you will have to let it sit 7-10 days before plasticity develops.  

Tom

Share this post


Link to post
Share on other sites

Yes, I was watching the stove very closely and the one piece that glowed that hot was a very small, 2 inch, thin piece and I took it out and let it cool, spread the fire put some and let some heat out.  lol I never expected it to glow that color. lol And... that piece still broke the next day. My brain is fried tryin to figure out how I can rip on it after it cools, TRYING to break it... it does not break so it fools me into thinking I finally got it... then the next day I'm holding it in my hand, and snap.... No water was added, either.  Urf. 

I will try the additive listed above and see what that does. I sold a pig today but that went to feed. So when I sell more pigs. 

Share this post


Link to post
Share on other sites

It's probably a tossup for you on whether Georgie's (Portland) or clay art center (Tacoma) are closer, but both have frit, om4 and talc.  Frit will be the most expensive, but at 20% it shouldn't be too bad, 10lb bag should be like 20 dollars, 10 pounds of om4 probably 5 bucks, same for 10 lbs of talc.  So maybe 35-40 bucks is all it would take to do some experimenting.  Those percentages above would be dry weight, so while you save up for it, sieve and dry some of your clay so it's ready for when you get the materials.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×

Important Information

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