Sunday, June 29, 2008

Native clay processing on a large scale

Back in the late '90's I was working as a potters apprentice in the New Mexico desert and one of my jobs was digging and processing native terracotta and stoneware clays.  Some of these clays were over an hour drive away.   I spent many hard weeks screening and processing native clay until I figured out the method that worked best for me.

If you plan on working with native clays there is a lot of testing involved but a simple way to decide if it's worth the extra hours of processing is to begin with a small sample. Make a small moist ball of clay, roll it and see if it sticks together well.  Next flatten it with your fingers, are there a few small cracks or large cracks in the ball?  If on the small scale it may be worth taking the next step, testing, which I will cover in another post.

The best method to collect clay for processing is to dig it dry, if it's not, you will have to completely dry it before moving on.  Assuming you are working with a large quantity of native clay you will need a few supplies to get started.  2 large plastic garbage cans with lids, 2 screen frames (2' by 2') of different mesh (expanded steel and a metal window screen) a couple of 2" X 4" about 3' long, a sturdy 1-2 quart container and lots of water.  Remember to keep this whole operation in close proximity.

Fill 1 garbage can 1/2 full with water and shovel in the dry clay.  Wait 1-2 days for the clay to "slake" down or completely break down into a fine slurry with the lid on.  The clay will settle to the bottom leaving clean water on the top.  Syphon off the top 2/3 of the water and then mix the clay with a shovel to create a uniform slurry.  

Now, take the other garbage can and place the 2' by 4's on the top rim.  Next place your expanded steel frame on top of the 2' by 4's.  With your quart container collect the slurry and pour it onto the screen.  The clay slurry will fall through but the rocks and other organic matter will get caught.  Clean the screen now and again buy dumping out the rocks  *If the clay you are working with is very fine with few rocks you can skip the expanded steel mesh and go to the window screen just add more water to your slurry.

After you have completely screened your clay through the expanded steel it's now time to do it all over again with the window screen.  I never said it wasn't tedious or hard work.  Simply clean out the first garbage can and screen into there.  At this point your clay should be free of debris.  Let the clay slurry settle for a day or more with the lid on and syphon off as much water as you can. 

For the drying process I recommend that you build another expanded steel frame with 2' by 4's.  Create a frame that is 2' X 4' X 4".  Nail the expanded steel mesh to the bottom of the frame with horseshoe nails and line the bottom and sides with an old bed sheet, staple into place. Prop your frame up on 4" X 4"s or make legs.  Now, using your quart container pour the slurry into the bed sheet and let the water drain out the bottom.  Keep the frame covered with a piece of plywood to keep debris out and add more slurry as needed.  In a few days the clay should be moist for wedging and it will peel away from the bed sheet.  Now wasn't that fun! 

It's been years since I processed literally thousands of pounds of native clay but it's a technique I will never soon forget.  Next year Jeff and I hope to move to our land near Alfred, NY.  Lucky for me it is all native terracotta clay that needs processing.

Why you shouldn't mix kitchen tools with the studio

I came across some old handouts I made for my students this morning and was instantly reminded of a personal experience I had 8 years ago involving black copper oxide and my coffee cup.  Here's a good lesson why one should never mix kitchen items with their ceramic studio.

Back in 2000, Jeff and I were living in our camper in New Mexico.  I was creating some small clay pendants and brushing them with a black copper oxide solution I mixed in my coffee cup.  You know I like coffee.  With a limited amount of space and available water we did not always wash the cups.  The next morning Jeff made coffee and poured a steaming hot cup into my glass.  Oh, yummy.  It tasted fine until 10 minutes later when I started to get abdominal cramps.  I slowly crumpled into the fetal position as the cramping increased in severity to the point that I could barely breathe.  The entire experience lasted only 15 minutes but it felt like an eternity.  Needless to say the "coffee" residue in my cup was in fact black copper oxide, something I entirely overlooked.  

Without daily access to the world wide web back then it took me 3 days to get the MSDS sheet on black copper oxide.  Fortunately no serious harm was done.  I learned my lesson painfully well and consider myself fortunate that it wasn't something more serious.

So, if you plan on using any kitchen items I strongly recommend that you go to the thrift store and purchase a second set for the studio.

Saturday, June 28, 2008

Pottery tools for wheel throwing

Okay, every craftsperson needs tools, I have a whole drawer full of them.  Some are purchased, some are made and some come from the kitchen.  How many tools do you really need for pottery?  Well, every potter is different and we each have our own favorite tools.  

For throwing on the wheel I have a few basics, a wire, a pin tool, a kemper KWT6 wooden scraper and kempers RB5 wooden rib, a custom crafted stainless steel metal rib, a sponge and a "sponge on a stick".  And of course, my old jalopy of a potter's wheel circa 1970 from Newton's Potter's Supply.  It's old, it makes noise, it's hard to clean, it was free and I love it.

Now, to get a basic understanding of the tools...

The pin tool- can be used for checking the thickness of the foot of the pot.  It also calls for drastic measures when your pot is so far off center that the lip is has an entire 1 inch variance in height, we use this tool to trim the lip of the pot and make it visually appear as though the pot is nearly centered.  *Note- This simple trick of the trade does nothing to make the trimming process easier if your pot is off center.  Best to just begin from scratch and learn to center properly.

The Kemper KWT6 scraper- a great tool for carving away excess clay on the foot of your pot.  Use it while the wheel is spinning and make a small grove at the base for the wire tool to pass under.

The Kemper RB5 rib tool- I only use this tool when making bowls.  After finishing the thrown bowl and sponging away the excess water I carefully run the curved rib along the inside from top to bottom to remove the slurry and create a nice contoured shape.

The wire tool- I use this for cutting down 25 pounds of clay and for cutting my finished pots off the wheel head or bat head. Always have an extra one of these handy.  Be forewarned, when the wire frays eventually it will seriously puncture a finger just like a pin. 

Metal rib tool- This custom crafted tool is basically used with throwing as well as removing the slurry from the outside of a pot so it can be hand lifted off the wheel.  There is a complex  method to using this tool which I won't elaborate on here.

Sponge tool- Natural sea sponges are really nice, however, they are not eco- friendly.  I use a simple 1" foam padding from a fabric supply store purchased in 4' by 4' lengths and cut it down to size.  One of these little sponges last me a whole year and costs only pennies.  

Sponge on a stick-  This is a great tool for removing excess water from the inside of tall pots or narrow necked pots.  I prefer to make my own as opposed to the commercially available ones.  It's so simple to make, all you need is a wooden craft dowel approx. 1/4 diameter and 12" long, a rectangular piece of sponge and an elastic band like the ones that come with bunches of broccoli.  Roll the sponge around the stick and wrap the elastic around and leaving 1/2" from the base.  That's it and the best part is that it won't fly off the stick when the wheel is spinning.

These are my preferred wheel throwing tools, again, everyone has there favorites.  If you are just beginning to make pots on the wheel a basic kemper tool kit will suffice.  And a simple note on wheel direction, if you are right handed you want the wheel to spin counter clockwise and throwing is done in the 3 o'clock to 4 o'clock position.  Vise versa if you are left handed.

The Creative Process

For me, the creative clay process begins first thing every morning with a cup of coffee and a notebook.  Still in my sleepy slumber, I scribble away drawing designs and pottery forms on scrap pages of paper.  If I like one of my designs I take it further and draw it on graph paper, estimate the dimensions and weight of the clay necessary.  By drawing on graph paper, straight on, I can see the two dimensional proportions of the foot, belly, shoulder and lip of the pot.  This is a simple technique I learned while working in a production pottery.  After creating a few pots on the wheel, I note the actual weights and dimensions with a ruler.  These notes and drawings also make an easy reference to go back to in the future to produce similar works of relative proportion.

Granted, this technique of graph paper drawing can hinder the creative zen while working with clay, however, it's something I can do on a day when I am not getting my hands dirty.