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SLAB ROLLER EXPERIMENTS

While presenting at the Potters Council Handbuilding workshop at the Spruill Center in Atlanta, my students and I began discussing the effects we believed a slab roller had on the clay it was compressing and extending.

We were wondering just what was happening to both sides of the clay and what effect being stretched in one direction had the clay. I kept wondering about this after I got home and decided to try a couple of simple experiments. In order to see how the clay was moving through the rollers I decided to place some colored clay on both sides of a plain slice of clay like this.

                              position

Then. I ran it through my Bailey slab roller.


slab rol 1slab rol:2

After compressing and stretching the clay, I found each surface was different. The pattern on the top of the clay had stretched 7" while the pattern on the bottom of the clay had only stretched 4 1/2".

top  bottom

Notice ... not much size difference side to side..

I decided to flip the piece and roll it again without changing anything else.

2 Bot:top  2 Top:Bot

Now the design is 8" on the original top and 6.25 on the original bottom.

Obviously, the piece was compressed more on its length than its width. So, I wondered what this meant to the shrinkage of a piece of work.

I cut it into a 6" by 6" tile and let it rest. After 30 minutes it had shrunk 1/16th inch on all sides. Next day , it had shrunk 1/8th inch on all sides.

Fin Bot

Even shrinkage and FLAT ... absolutely no warping.

SO ... why did something that appeared to stretch unevenly shrink so evenly? Is the conventional wisdom of rolling again across the grain really a necessary step if this tile stayed perfectly flat without any help?

My husband, the engineer, speculates the slab roller is all about compression, not stretching so this is why it stays even.

 Next experiment will be with stripes so I can examine the center of the slab to see what happens to the clay in the middle.


April/ May 2010

I've just colored 500 pounds of clay !!

clay stains 

palette     colored clay

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LOVE THE BRIGHT COLORS!

Many times people ask me why I pay a higher price for Southern Ice Porcelain. Here is the reason ... same % of stain added to both clay bodies ... Southern Ice is on the right in both images.

pink     yellow

 

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I have  CONGRATULATIONS  to send out ...

First to  Evan Dubchansky of the The Buckley School in Sherman Oaks, CA who received the "Chris Campbell Award for Colored Clay" at the K12 Exhibition in Philadelphia.

wide

Second to Ellen Mahoney, his teacher, & Art Department Chair.  

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May 5, 2010 2:46 PM

Jan/Feb 2010 Murrini

I started designing a new murrini pattern in January and thought you all might enjoy watching the on going process.

It all starts with a sketch ... this took about 4 hours.new - 1 I wanted to have it look like a ribbon falling to the bottom of the vessel. I wanted the color change to be gradual and for the flow of colors to have movement.




Here is the final sketch of the pattern without any color choices. This is the actual size the pattern will be on the finished pieces. All the measurements have been made with allowances  for the shrinkage of the Southern Ice Porcelain.




new - 2This is the color shift want to achieve, so the next step is to build a murrini loaf with these colors. In order to get this look, the loaf was built from a hundred and fifty slices of colored clay.



Once the loaf is built, I cut a slice and fired it to make sure the colors were correct. This step is crucial since it would be a total waste of time to do all the work in building the murrini, only to find out the colors were off. As it happens, I did have to edit the colored loaf to cut out parts I was not happy with.

colored loaf

During the first week in February I created the large white and colored loaf. Once again I proved to myself that sketching a pattern with paper and pencils is a lot easier than executing the pattern with wet clay, slips and thin slices of color. It got a little crazy for a while!


The final loaf is resting now. It's never a good idea to mess with it right away. 

large loaf

As you can see,  the outside looks terrible. I will not know what I have until I see an inside slice of it. Nightmare or lovely ... got to wait.


Today is the day though. After I finish writing this I will head in to my studio to cut into it. Images later ... if it works out!

NEXT DAY ....

Here is the loaf with a slice in front. The pattern looks backwards in the loaf, but you just have to flip the slice to get right side around.

murrini     new - 2 copy

I will be making some test vessels today to check for design and size.

To see the rest of the story, go to the MURRINIS 2 page to see these vessels being built.

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ARTIST'S STATEMENT

Today, I received an e-mail asking for my artist statement. I didn't currently have one.

Statements somehow propel otherwise sane artists into the realms of ancient Latin. They mean well but often end up describing their work in terms both off-putting and incomprehensible. Really, should you have to pull out a dictionary to understand what an artist is trying to do?

So as I explained to Rachel why I did not have one, I inadvertently wrote one.

"Basically, I do what I do because there is nothing else that fascinates and challenges me as much as colored porcelain. I've been working with it for 20 years and still have not come close to trying everything I want to do ... there seems to always be another question, another idea. It's just so much fun."


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Feb 9, 2010 11:50 AM

BLOG ... BLOG ... BLOG

Do you always have to mix colors thoroughly?

The Mason website has listings of all the colors available with a guide showing which ones are suitable for using in clay bodies and which ingredients to avoid in your clear glazes. 

Why does this matter? Every clay body has ingredients in it that can react to a colorant. Sometimes that lovely pink fires green or the blue fires pink because of it. If your clear glaze has the wrong ingredient in it, it will change the colors or bleed them. 

You can be reasonably safe if you stick with their guidelines, but safe is not always fun. I have tried dozens of other stains with great results. The trick is to test every single batch you blend in order to see what happens to the color with and without a glaze. Then you can decide whether to keep using it or not.

I had a pink stain that fired the most lovely pale green. I liked it and kept using it, but since I have the attention span of a gnat, I quickly forgot the pink was really green and ruined a pattern with the wrong color.

This is why I use  the ones that look like the end product.

I would encourage you to buy an ounce or so of different colors and give them a try. Some are incredibly beautiful and are colors you cannot achieve by simply mixing two primaries. 

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Do you always have to mix colors thoroughly?

No. You can mix them in many ways and get great results.

Mixing them in wet or dry you can stop at any point to achieve swirls of color or  small specks of color through the clay. You can thoroughly mix the colors then gently  knead it into white, stopping when you like the pattern. 

mixswirl

Set a bit aside to dry then crush it and knead it back into the white clay for yet another look. You can add multiple colors dry or wet. I have scraped swirls off dry clay and pressed them carefully to keep the shape. There are no rules, so try anything.

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You cannot reach Alaska just by wandering North. You need a map and a plan.”

I believe in the power contained in the simple act of writing down your goals, so I strongly encourage you to do it. Too many years slip past with no evident markers. You can feel as though you have not accomplished anything when in reality, you have. You just don’t have any way of knowing if you have not kept track of your plans. Give yourself this gift in January so you can enjoy it next December. 

The map is a simple statement of your goals. The plan is a list of steps you need to take.

Make the goals realistic and the steps achievable. Don’t defeat yourself by setting huge goals with impossible deadlines. If you finish reasonable goals early, you can make a new plan. 

Post this plan somewhere you will see it every day.

Have a fat marker nearby so you can cross out steps when done. 

Of course the first goal is to make a plan, so that is one line you can stroke out immediately after you are done!


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Q: Why color your own clay? There are places to buy it pre-colored and that seems like a lot less work.

Yes, you can buy pre-made colored clay and there is nothing wrong with doing so. The reason I don't is because I want to choose my own colors, have them as dark or as light as I want and I want to use my own porcelain clay body.

color chartwebSAMPLESweb

One supplier I called would not tell me what the basic clay body was that they were making it from. Without this information it is impossible for me to lighten their pre-set color or use white along with it to make a pattern.

I like vibrant colors and use a lot more Mason Stain by % than they do. I can always lighten them up by adding white.

Even though it is a messy job, it is also a very simple job to color clay.

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Dec 30, 2009 12:11 PM
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