Testing the wet to bisque shrinkage rate of native clay

To quote Michael Cardew from his fantastic book, Pioneer Pottery,"An unknown clay should be presumed guilty until proven innocent." Commercially available clays often have the shrinkage, porosity and absorption rates listed in there catalogs, the work has already been done. But what about a unknown native clay?

In the near future my husband and I will be moving to our property in western New York state. Our parcel is filled with native terracotta clay and shale. As a potter this is a potential gold mine for me but I don't know much regarding this particular clay body. Is this a clay body I can use for throwing on the wheel, what temperature does it fire to? One thing I am certain of is that there were local potteries in the old days so chances are pretty good that I can utilize this clay.

After finding a nice pure vein of clay I was able to do a simple plasticity test by rolling out a wet coil and checking for cracks, it passed. Refer to my previous post- "Native clay processing on a large scale". My next step was to make a couple of small balls and bisque fire them in my kiln to cone 05. I fired these small balls of native clay inside a commercial clay bisque fired bowl as a precaution. I did not want the clay to melt and ruin my shelving, I could sacrifice the bowl. The clay survived and fired to the same rich red coloring as my commercial terracotta clay body. Now it's time for some more testing.

To test the shrinkage rate of a native clay works on averages and does not involve complex formulas, thankfully. To take from Tom Buck, Leon Nigrosh and Michael Cardew begin by rolling out a slab of native clay that is 1 cm thick. Allow the slab to set up for a few hours before cutting out your test tiles. Take a piece of box board and cut a rectangle 13 cm long and 4 cm wide. This box board will be your template for the tiles. Using a fettling knife cut out as many tiles as you can, preferably 10. Next draw a line 10 cm long down the middle of each test tile. Set them aside to stiffen up to the point of handling.

Thinking ahead to porosity and absorption testing were going to kill 2 birds with one stone. Label each test tile A, B, C, D and so on. Using a triple beam or digital scale weigh each tile in grams in it's wet state and write it down, always keep notes. Completely dry the tiles flipping as needed and/ or weighting them to prevent warpage. After the tiles have completely dried, measure the 10 cm lines (100 mm) and weigh them again. Example- Tile A is 96 mm (-4 mm), Tile B is 97 mm (-3 mm), Tile C is 95 mm (-5 mm). The average difference of A+B+C+D+E+F+G+H+I+J =X divided by the number of tiles equals your wet to dry shrinkage in percentage. Example- in mm- 4+3+2+3+4+3+2+3+4+3= 31 divided by 10 = 3.1% wet to dry shrinkage.

Next we are going to fire the test tiles in the kiln to bisque temperature, cone 05 or cone 04. After the kiln has cooled and you have removed your tiles measure each 10 cm line again and weigh the tiles again. Tile A is 89 mm (-11 mm), Tile B is 90 mm (-10 mm). Again, take those averages and divide by the number of tiles. This percentage will give you the average wet to bisque shrinkage rate. Somewhere in the range of 10- 15% is good and worth investing the extra time for glaze firing and absorption and porosity testing which will be part of my next post.

Sponge on a stick, Throwing Tool

One of my favorite pots to throw on the potters wheel are narrow neck vases. Any one who makes wheel thrown pottery knows that all the free standing water within the vessel needs to be removed before cutting the pot free from the wheel head. Failure to do so will result in a cracked bottom as the clay absorbs all of that free standing water.

Commercially available sponge on a stick tools (does this have some other name?) are too wide for removing the water from the base of a narrow neck vase and they have the tendency to roll around while the wheel is spinning. I devised a very simple, inexpensive and quick method of making my own sponge on a stick tool that is narrow enough not to damage the neck of my vase when inserting it.

Three simple materials are all that is needed- 1" thick foam found at fabric stores and often sold in 2' X 2' pieces. You will need a strip approximately 2" X 3" X 1" for the making of the tool. Don't despair, the remainder of the foam can be used for throwing sponges, cleaning and as padding for pots. These sponges last for years before giving way. You will also need a 1/4" thick wooden dowel approximately 1 foot in length. And lastly, a thick elastic band like the ones that come with bunches of broccoli at the grocery store.

Simply roll your strip of foam around the dowel (2" thickness, 3" length) leaving 1/2" to 3/4" of the sponge to overhang the end of the dowel so that it will not puncture the base of your pot. Secure in place by wrapping the elastic around the top half of the sponge.

This simple tool only takes minutes to create and pennies to make. Make them as thick or as long as you need them. In the image my larger sponge tool is about 5 years old and still working just fine. The best part is that I can insert it into my narrow neck vases without damaging the neck and it won't roll around inside the pot while the wheel is spinning. Happy tool making.

Patience is a Virtue

I just finished a low fire glaze firing early this afternoon and I am so anxious and excited to see my wares completed.  However, I have to wait until tomorrow morning before cracking the kiln.  

Many folks don't realize just how many steps are involved with pottery and ceramics.  I've always wondered just how many steps there are in making a pot, so here goes.

1- Purchase or recycle clay

2- Soften clay for throwing

3- Wedge clay for throwing

4- Throw pot on the wheel

5- Remove pot from wheel and allow to air dry

6- Trim foot of pot

7- Add handles or stamp impressions etc.

8- Allow pot to dry completely

9- Clean up rough edging marks or bumps

10- Load kiln for bisque firing

11- Bisque fire kiln for 6-8 hours

12- Unload kiln and rinse pots

13- Put wax resist on pots

14- Prepare glazes and glaze pots by dipping or brushing 3 coats

15- Load kiln again for glaze firing

16- Fire kiln for 6+ hours

17- Patiently wait to unload kiln

Okay, there are approximately 17 steps in the basic creation of a pot.  I did not include the methods of recycling clay, cleaning the wheel and equipment, the making of glazes, or the cleaning of the kiln and shelves.  Then there are the additional steps of selling your wares either in shows or online, taking photos, writing listings, figuring out expenses and shipping costs etc.  

I suppose that with anything we do in life there are many steps involved. One of the many aspects of ceramics that I truly appreciate is how it encompasses earth, water, air, fire and metals. If I am not mistaken it is the only craft that encompasses all of those elements.

I'm afraid I patiently have to wait out the night before opening the kiln.  It's my hope that these wares will be 95% successful and then I can take photographs and start my listings on Etsy.

Clay Stamp Crafting for the Home Studio

Alright, I have been pretty lazy lately about my blog and today I was determined to create an entry.  What I didn't expect was that when the inspiration hit I could not get into blogger. After hours of waiting, here I am, finally and my inspiration is lacking.  It could also have a lot to do with the fact that I was out until 2 AM on Saturday morning.  Yep, I still have not recovered from that late night of good conversation and laughter with new friends.  I'm just not used to staying up so late.

Anywho, I really wanted to talk about clay stamp making.  Lately I have been browsing my supply catalogs and seeing a lot of bisque stamps available.  Stamps are on the expensive side but there can be a lot of work involved in making the masters depending on how intricate they are.  I'm the kind of person who enjoys crafting my own clay tools when I can and stamps are something I have been making for years.  

Here's a pretty simple method of crafting your own personalized ceramic bisque stamps for use on pottery and hand built ceramics. This technique will allow you to make the first negative impression of your designs.  Roll out an even slab of smooth earthenware clay, the larger the slab the more designs you can create.  Allow it to air dry for a few hours almost to the point of leather hard stage.  Taking a sharp pencil and draw or carve a design into the leather hard slab. You can pre draw your designs on paper or print them up from your computer.  Simply place the paper on top of the slab and lightly retrace the design with a pencil.  By removing the paper you can then go in and make the lines deeper, tracing allows you to get the line proportions correct.

The pencil or any carving tool will leave behind some rough edging.  After the slab is dry, gently scrape away the raised rough edges with a trimming tool. To remove the clay dust left behind in the carved designs, gently pat the slab with a moist piece of clay.  After this is done you can further clean the edging with a damp soft bristled paint brush.  At this point I recommend you fire your clay slab in the kiln before making positive stamp impressions or you may run the risk of breaking your slab and ruining all of your new designs.  Been there, done that.

To make the positive after the bisque is completed roll out a fresh coil of clay which has a higher moisture content than you would normally use for throwing or hand building, this will limit the cracking around the edges when you make the impression.  Your coil should be approximately 1" thick and  2" long.  Flatten it into the stamp impression allowing yourself a few finger holds.  Another method is to make a flat slab and press it or roll it with a rolling pin into the impression.  After it stiffens up you can remove the excess edging and add a finger hold to the back by slipping and scoring.  Once you create a good impression set it aside to dry and bisque fire your new stamp before using. 

Crafting your own ceramic stamps can be a intricate as you desire just remember that they do not need to be perfect to make a nice impression on your work of art which will be covered with glaze.  

Ye Olde Shanty Shack, Home Sweet Home

It's early, maybe even too early but the chirping Robins outside my window don't care about my rest.  They are too excited for a brand new day to begin,"wake up everyone, the sun is rising!" Chirp, chirp, chirp.

In my morning slumber with a cup of coffee in my hand and notebook in my lap I began to daydream of the days past.  I was thinking about my beginnings in New Mexico, my friendships, freedoms and lessons learned.  My early 20's.  Those were difficult lessons and often they were difficult to swallow.  Equally they were some of the best times I ever had.  I flew with the wind.

Maturity is humorous in retrospect.  In our teens we know everything about everything.  In our 20's we realize we know nothing.  Our sheltered view of the world is not one of reality.  In our 30's we begin to get comfortable in our own skin and learn that it's okay to say no without going into a guilt ridden downward spiral.  Our 40's, well, those lessons are still years away for me.

In my 20's I did something most unexpected and somewhat uncommon compared to others my age.  I packed up and left college due to my many disappointments at the University and found a potter to apprentice with.   He taught me a tremendous amount about clay and firing, his name is Jarrett West.  Jarrett has more spirit and enthusiasm for clay and life than anyone I have ever met. 

In my apprenticeship with the West family, my friend and I needed a place to live.  We were granted permission to put up a tipi or build a temporary structure on their land.  Build a temporary structure we did.  The shanty shack, complete with attached dog shack on the outside.  

The shanty was an 8' X 10' structure that cost us about $80.00 to build and was primarily constructed with recycled building material.  We had scrap pieces of rusted tin complete with multiple holes, plywood, a broken door, old windows and an old gymnasium hardwood floor. The flooring was the centerpiece of the shanty although hardly enough space to play a game of basketball.  Inside we had bunk beds, an old wood stove for heating and cooking, shelving and a milk crate to lounge on.  

Much of our time was spent surviving and taking care of our daily needs.  Gathering firewood in the arroyo, hauling in water by hand, preparing dinner, washing dishes and taking solar showers. Water was most precious and the minimal waste of it was of the utmost importance. There was such a simplicity and honesty in those daily chores, something that takes minutes to do in a conventional home took us hours to complete.  I loved it and in many ways miss the challenges of simple living.

To me, life in the shanty shack was a way of testing myself.  It was a cleansing of my selfish and over indulgent ways and attitudes.  I had to learn that happiness can only be found in your heart and contentedness could only be found within.  Could I survive in the world?  What did I truly need to survive in the world?  In those 6 months that I lived in the shanty shack I learned that I needed water, food, warmth, friendship, good health and love. After that I knew that I would be okay.

As the years have flown by there have many other hardships and challenges in my life. During those times I reflect on the shanty with fondness and remind myself that I have what I need.  Someway, somehow, as I am getting older and a smidgen wiser my life has become more complicated and my responsibilities greater.  I'm still figuring out who I am and what I desire but one certainty is that I have what I need and more.

Inexpensive shelving for your craft space

Okay, I have been slacking on my blogging lately.  It's not because I am lazy, simply that life has been a little chaotic these last few weeks. 

I recently participated in a clean your craft space day forum on Etsy and someone commented on my shelving.  It's not pretty or perfect but it is functional as well as inexpensive to build.  I have over 78 feet of shelving space that cost less than $100.00 to construct.

Somethings you will need for this time consuming project.

1- A handy guy or woman, if you are not.

2- A circular saw, a drill press, electric drill, a pipe cutter or a jig saw, tape measure, safety gear.

3- 2' X 4's,  3/4" conduit pipe, 2 1/2" sheet metal screws and MDF shelves or MDF sheets, you can also substitute 3/4" thick plywood for the MDF if you can afford it.

Construction needs to happen outside due to metal chipping and sawdust.  If you have ever cut MDF you know what I am taking about, it's made from sawdust and it makes a ton of sawdust.  For shelving that is longer that 5 feet expect your MDF to warp a little.

Basically the the 2" X 4"s screw into the studs of your wall and act as peg holders.  The conduit pipe pieces are your pegs and the MDF or plywood is your removable shelf. 

Most importantly you need to know what kind of shelving is appropriate for your craft. How much space do you have available? How much height do you need between shelves? How many studs, pipe pieces and shelf footage do you need?

For example, we are going to create 6 shelves that are 4 feet in length and 10" wide and spaced 1 foot apart.  For this project you will need two 2' X 4' X 8's, Twelve pieces of conduit pipe that are 11" in length (11 feet of piping), six shelves that are 10" wide and 4 feet in length which can be cut out of a 4' X 8' piece of MDF or plywood.

Begin with the pipe cutting , 12 pieces 11" in length.  You will need a jig saw with a metal blade to cut these or a pipe cutter.  A round file or dremel tool is also good to deburr the ends. The tricky part is the drilling of the 2" X 4"s.  Take into consideration whether or not you have baseboard in your measurements as well, you will need to screw the studs above the baseboard. You really need a drill press for this part, drill the holes in the center spaced 1 foot apart, slightly smaller than the width of the conduit pipe and know which end is the bottom and the top of the stud.  After the holes are drilled, pound in the conduit pipe pieces.  There should be approximately 9 1/2" of pipe sticking out of the stud ready to support a 10" wide shelf.  Now you need to screw the studs into the wall studs.  Often times these are spaced on 16" centers if you're lucky.  And lastly place your shelves on top of the pegs and your ready to begin filling them up and asking for more shelving.

It's an in depth process that requires resourcefulness and know how if your not a talented carpenter.  Even though mine are not perfect, no surface in our home is level or square (old 1800's house) I do appreciate not living out of boxes anymore.  Of course, an easier method would be to simply purchase 12 heavy duty shelf brackets.  Nothing in my life is ever that simple, it's just how I am.  I am a process and learn kind of gal.

Couch Potato

This is how I am feeling today.  I kind of wonder if I wouldn't be better off simply relaxing on the couch than attempting any more projects today.  It's just that nothing is coming together no matter how hard I fight against it.  Hmm. 

I could give it one more try... 

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.

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.